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282 Cards in this Set
- Front
- Back
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Protection provided by immune responses that mature throughout life; involves B cells and T cells.
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Adaptive Immunity
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Y-shaped protein that binds antigen
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Antibody
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Molecule that reacts specifically with either an antibody or an antigen receptor on a lymphocyte
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Antigen
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A group of white blood cells (leukocytes) that have antigen-specific receptors on their surface; includes B cells and T cells
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Lymphocyte
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Antigen-presenting cells: Cells such as B cells, macrophages, and dendritic cells that can present exogenous antigens to naive or memory T cells, activating them
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APC's
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Type of lymphocyte programmed to make antibodies
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B Cells
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Immunity involving a T-Cell response
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Cell-Mediated immunity
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Process in which a lymphocyte's antigen receptor binds to an antigen, allowing the lymphocyte to proliferate
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Clonal selection
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Type of lymphocyte programmed to destroy infected or cancerous "self" cells
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Cytotoxic T Cell
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Cell type responsible for activating naive T cells
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Dendritic Cell
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White blood cells
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Leukocyte
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Type of lymphocyte programmed to activate B cells and macrophages, and assist other parts of the adaptive immune response
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Helper T Cell
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Immunity involving B cells and an antibody response
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Humoral immunity
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Cell surface molecules that present antigen to T cells; includes MHC class I molecules and MHC class II molecules
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Major Histocompatibility Complex (MHC) Molecules
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Long-lived descendants of activated lymphocytes that can quickly respond when a specific antigen is encountered again
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Memory Lymphocytes
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Effector forms of a B cell; it functions as an antibody-secreting factory
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Plasma Cell
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Effector form of a cytotoxic T cell; it induces apoptosis in infected or cancerous "self" cells
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Tc Cell
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Effector form of a helper T cell; it activates B cells and macrophages, and releases cytokines that stimulate other parts of the immune system
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TH cell
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Host defenses involving anatomical barriers, sensor systems that recognize patterns associated with microbes or tissue damage, phagocytic cells, and the inflammatory response.
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Innate immunity
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Programmed death of "self"cells that does not cause inflammation
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Apoptosis
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Cell death that does not cause inflammation
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Apoptosis
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how long does it take for adaptive immunity to build?
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A week or more
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An important characteristic of adaptive immunity. A stronger response to re-exposure.
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Memory
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Series of proteins in blood and tissue fluids that can be activated to help destroy and remove invading microbes
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Complement system
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Proteins that function as chemical messengers, allowing cells to communicate
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Cytokines
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Coordinated innate response with the purpose of containing a site of damage, localizing the response, eliminating the invader and restoring tissue function. The signs of inflammation are swelling, heat, redness, and pain in the infected area.
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Inflammatory response
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In which type of immune response does the inflammation process take place?
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Innate immune response
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What are the signs of inflammation
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swelling, heat, redness, and pain in the infected area.
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Host defenses involving anatomical barriers, sensor systems that recognize patterns associated with microbes or tissue damage, phagocytic cells, and the inflammatory response.
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Innate immunity
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Type of phagocytic cell that resides in tissues and has multiple roles, including scavenging debris and producing pro-inflammatory cytokines
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Macrophage
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Any group of cytokines that contribute to the inflammatory resonse.
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Pro-inflammatory cytokines
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Complement system components that assemble to form pores in membranes of invading cells
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Membrane Attack Complex (MAC)
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MAC
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Membrane Attack Complex
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Major type of phagocytic cell in blood; neutrophils quickly move to infected tissues to destroy invading microbes.
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Neutrophil
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Coating of an object with molecules for which phagocytes have receptors, making it easier for phagocytosis to occur.
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Opsonization
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Proteins on or in cells that recognize specific compounds unique to microbes or tissue damage, allowing the cells to sense the presence of invading microbes or damage.
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Pattern Recognition Receptors (PRR's)
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PRR
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Pattern Recognition Receptors
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Cell type that specializes in engulfing and digesting microbes and cell debris
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Phagocyte
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The process by which a phagocyte engulfs an invader
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Phagocytosis
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Cells that eat
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Phagocytes
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Preventing disease by exposing a person's immune system to harmless forms of the pathogen or its products.
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Vaccination
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Why can influenza be contracted repeatedly?
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The pathogen's ability to continually evade the host defenses.
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Which immune response has molecular specificity
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Adaptive immune response
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The ability to ignore any given molecule
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tolerance
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The ability of the immune system to distinguish normal host cells from invading microbes
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Self versus non-self recognition
or "healthy self" versus "dangerous". Dangerous includes invading microbes as well as cancerous or other "corrupt" cells |
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Why is it important to have cell tolerance?
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without it the immune system would routinely turn against the body's own cells, attacking them just as it does invading microbes.
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The primary participants in the adaptive immune responses
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Lymphocytes
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First response to a particular antigen
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Primary response
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Two basic strategies for countering foreign material used by the adaptive immune system
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Humoral immunity and cell-mediated immunity (CMI)
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CMI
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Cell-mediated immunity
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Works to eliminate extracellular antigens
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Humoral immunity
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Deals with antigens residing within a host cell such as a virus infecting a cell
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Cell-mediated immunity
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Other name for B cells
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B lymphocytes
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Which cells of the adaptive immune system are responsible for humoral immunity?
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B cells
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Where do B cells develop?
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bone marrow
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B cells differentiate into what kind of cells?
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Plasma cells
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These cells function as factories that produce Y-shaped antigens
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Plasma cells
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Y-shaped proteins
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antibodies
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Long-lived B cells that respond more quickly if the antigen is encountered again
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B memory cells
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How many function regions do antibodies have?
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Two. The two identical arms and the stem.
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What are the two regions of antibodies
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Stem and two identical arms
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Where is the sequence of amino acids located on an antibody that makes that antibody unique?
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The end of the arms called the variable region
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What provides a basis for the specificity of antibodies?
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The amino acid sequence of the end of the antibody arms or the variable region.
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Which cells of the adaptive immune system are responsible for humoral immunity?
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B cells
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Where do B cells develop?
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bone marrow
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B cells differentiate into what kind of cells?
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Plasma cells
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These cells function as factories that produce Y-shaped antigens
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Plasma cells
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Y-shaped proteins
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antibodies
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Long-lived B cells that respond more quickly if the antigen is encountered again
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B memory cells
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How many function regions do antibodies have?
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Two. The two identical arms and the stem.
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What are the two regions of antibodies
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Stem and two identical arms
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Where is the sequence of amino acids located on an antibody that makes that antibody unique?
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The end of the arms called the variable region
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What provides a basis for the specificity of antibodies?
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The amino acid sequence of the end of the antibody arms or the variable region.
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Give an example of a direct mechanism and an indirect mechanism used by antibodies to protect the host
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Direct: their ability to bind antigens and coating them, thereby preventing it from attaching to a host cell. An antibody-coated viral particle cannot attach to its receptor, and therefore can not enter the cell.
Indirect: due to the "red flag" region tagging the antigen for elimination. |
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BCR
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B Cell receptor
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A membrane-bound version of the specific antibody the B cell is programmed to make
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BCR B cell receptor
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What happens if a naive B cell encounters an antigen that its BCR binds? (very next step only)
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The B cell is triggered to multiply
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The type of cells involved in Cell-mediated immunity
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T lymphocytes or T cells
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Where do T cells mature?
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Thymus
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What are the two subsets of T cells?
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cytotoxic T cells and helper T cells
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TCR
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T-cell receptor
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Surface molecule which allows the cell to bind a specific antigen on T cells
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TCR T-cell receptor
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Which receptor, BCR or TCR, recognizes free antigen?
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BCR only. TCR must recognize an antigen being presented by other cells.
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What cells are responsible for T-cell activation?
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Dendritic cells
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Which type of immunity are dendritic cells technically part of?
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Innate immunity
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Effector helper T cells
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TH cells
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Effector cytotoxic cells
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Tc cells
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Can all three (B cells, TH cells and Tc cells) form memory cells?
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Yes
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These cells respond to intracellular antigens
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Tc Cells
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What do Tc cells do when an intracellular antigen is recognized in order to protect the host?
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Tc cells induce the "self" cell that harbors the antigen to undergo apoptosis. Ie viral infected cells.
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What is one positive side effect of sacrificing host cells which were infected with a virus?
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Unassembled viral components are released, provoking a humoral response.
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These cells are programmed to orchestrate the adaptive immune response
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Helper T cells
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How is the strategy of the cell-mediated response different from that of the humoral response?
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Cell-mediated sacrifices a host cell in order to prevent the spread of intracellular antigens. Humoral response involves phagocytizing the antigen.
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Why is it important that B cells and T cells be activated before they can mount a response against antigen?
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B cells and T cells can cause damage to host tissues, also they would attack self cells if not activated.
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How would you expect a Tc cell to respond if it encountered a TH cell that was infected with a virus?
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The Tc cell would prompt the infected TH cell to undergo apoptosis
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A collection of tissues and organs that bring the population B cells and T cells into contact with antigens
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Lymphatic system
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What is the fluid called in the Lymphatic system?
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Lymph
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How is a B-cell receptor similar to an antibody?
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It is a membrane-bound version of the specific antibody the B cell is programmed to make.
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Flow within the lymphatic system occurs via the _________.
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Lymphatic vessels, or lymphatics
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Explain where lymph fluid comes from.
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Capillaries filter the blood and supply tissues with the oxygen and nutrients carried by the blood. Most of that fluid then reenters the capillaries, but some enters the lymphatics instead. They lymph - which also contains white blood cells and antigens that have entered the tissues, travels via the lymphatics to the lymph nodes, where proteins, cells, and other materials are removed. The lymph then empties back into the blood circulatory system. Note that the inflammaotry response causes more fluid to enter the tissues at the site of inflammation; this causes a corresponding increase in the antigen-containing fluids that enter the lymph vessels
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The sites where lymphocytes gather to contact the various antigens
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Secondary lymphoid organs
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Give some examples of secondary lymphoid organs
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lymph nodes, spleen, tonsils, adenoids and appendix
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Lymph nodes capture materials from ___________ and spleen captures materials from ___________
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lymphatics; blood
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__________ capture materials from lymphatics and __________ captures materials from the blood
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Lymph nodes; spleen
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The anatomy of the secondary lymphoid organs provides a structured center for various cells of the immune system to interact and transfer _________
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Cytokines p 358
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The purpose of the secondary lymphoid organs
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To capture antigens and bring them into contact with lymphocytes.
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Where are Peyer's Patches located?
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Intestinal walls
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What are Peyer's Patches?
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Lymphoid tissues located in the intestinal walls that inspect sample of intestinal contents.
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What kind of epithelial cells transfer material from the intestinal lumen to the Peyer's Patches?
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M cells
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a network of lymphoid tissues which includes Peyer's patches?
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Mucoso-Associated lymphoid tissue (MALT)
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MALT
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Mucosa-Associated lymphoid tissue
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These play a critical role in mucosal immunity (the immune response that prevents microbes from invading the body via mucous membranes
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MALT
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The immune response that prevents microbes from invading the body via mucous membranes
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Mucosal immunity
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Lymphoid tissues located under the skin
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SALT Skin-Associated lymphoid tissues
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SALT
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Skin-Associated Lymphoid Tissue
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These lymph organs include the bone marrow and thymus
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Primary lymphoid organs
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These cells give rise to all blood cells
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Hematopoietic stem cells
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Where do hematopoietic stem cells reside?
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Bone marrow
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Where do B cells and T cells originate?
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Bone marrow
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Immature T cells migrate to the ________ to mature
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Thymus
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Where do immature B cells mature?
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Bone marrow
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Where do mature B cells go after the maturation process?
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Thymus
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Any molecule that reacts specifically with an antibody, a B-cell receptor, or a T-cell receptor
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Antibody
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Referring specifically to an antigen that elicits an immune response in a given situation
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Immunogen
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Two general categories of antigens
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T-dependent antigens,
T-independent antigens |
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If the responding B cell requires assistance from a TH cell, the antigen is _________________
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T-dependent
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If the responding B cell does not require assistance from a TH cell, the antigen is _____________
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T-independent
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________________ can activate B cells without TH cell help
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T-independent
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Examples of T-independent antigens, and why they are T-independent
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Lipopolysaccharide (LPS) and some carbohydrates. T-independent because of their repeating subunits
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Various antigens differ in their effectiveness in stimulating an immune respons. __________ generally induce a strong response, wherease ____________ often do not.
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Proteins, lipids
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Are antigens generally large or small molecules?
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Large
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Antigenic determinants
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Epitopes
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How is an epitope different from an antigen?
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An epitope is a discrete region of the antigen.
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Would a denatured antigen be expected to have the same epitopes as its native (undenatured) counterpart?
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No.
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Antibodies are often called ____________
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Immunoglobulins
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Two identical arms of antibodies
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Fab region
(fragments that are antigen binding) |
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The stem of an antibody
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Fc region
(fragments that could be crystallized) |
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All antibodies have the same basic Y-shaped structure called the
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Antibody monomer
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Two types of antibody chains
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Heavy chain, made up of heavy molecular weight polypeptides, and Light chain, made up of lower-molecular-weight polypeptide. Light chain makes up the outer part of the Fab region of the antibody
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How many domains do light chains have?
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Two each
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How many domains do heavy chains have?
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Four each
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Each light chain is linked to a heavy chain via ___________
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Disulfide bond
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One or more ___________ link the two heavy chains at the hinge region of the antibody
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disulfide bonds
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The portion at the ends of the Fab region of an antibody
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Variable region
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This accounts for the antigen-binding specificity on the antibody
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Variable region
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The antigen-binding site on the antibody is located where?
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At the end of the Fab's variable region between the heavy and light chain
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The antigen-binding site on an antibody attaches to what?
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Specific epitope of microorganisms
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How do antigen-binding sites attach to epitopes?
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Covalent bonds
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The constant region of the antibody
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Fc Region + part of the Fab region. All except the variable region is considered constant
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Why do we need a constant region of an antibody?
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Because it provides the body with something steady, consistent and recognizable even with the large number of antibodies present in the body
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List the five major classes of immunoglobulin
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IgM, IgG, IgA, IgD and IgE
(GAMED) |
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Immunoglobulin is another name for what?
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Antigen
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List six protective outcomes of antibody-antigen binding
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Neutralization, Opsonization, Complement system activation, Immobilization and adherence, Cross-linking and Antibody-dependent cellular cytotoxicity (ADCC)
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What is Neutralization in regards to Ab/Ag binding?
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Coating the toxin or virus with antibodies.
Toxins and viruses must bind specific molecules on a cell surface before they can damage that cell. A toxin or virus coated with antibodies cannot attach to cells and is said to be neutralized. |
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What is Opsonization in regards to Ab/Ag binding?
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The variable region of an IgG antibody attaches to a microorganism, and the constant region (Fc) sticks out and acts as an opsonin for phagocytes to phagocytize the mo.
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What kind of antigen is used as an opsonin?
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IgG
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What is Complement system activation in regards to Ab/Ag binding?
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Immune complexes where C1 protein binds and is activated to initiate the complement system.
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Another name for antigen/antibody complex
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Immune complex
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What is Immobilization and prevention of adherence in regards to Ab/Ag binding?
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Binding of antibodies to flagella interferes with a microbe's ability to move, and binding to pili prevents it from attaching to surfaces. Both can prevent infection.
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What is Cross-linking in regards to Ab/Ag binding?
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The two arms of an antibody can bind separate but identical antigen molecules, linking them. The purpose is to create a larger target for phagocytes
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What is Antibody-dependent cellular cytotoxicity (ADCC) in regards to Ab/Ag binding?
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When multiple IgG molecules bind to a virally infected cell or a tumor cell, that cell becomes a target for destruction by natural killer cells (NK cells). The NK cell attaches to the Fc regions of IgG and once attached kills the target cell by delivering compounds directly to it.
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How many immunoglobulin classes are there?
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5
GAMED |
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The first immunoglobulin class produced during the primary response to an antigen
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IgM
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IgM accounts for ________% of the circulating antigens.
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5%-13%
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The principle class of immunoglobulin in response to some T-independent antigens
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IgM
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Which immunoglobulin is a pentamer?
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IgM
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Which immunoglobulin has the primary role of controlling bloodstream infections and why?
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IgM because its large size prevents it from crossing from the bloodstream into tissues.
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How many antigen-binding sites does IgM have?
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10
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The most efficient class in triggering the classical pathway of complement system activation.
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IgM
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Can a fetus make IgM in utero?
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Yes.
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IgG accounts for __________% of the total serum immunoglobulin
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80% - 85%
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What is serum?
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the liquid portion of the blood
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Where is IgG usually?
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Circulating in the blood but exits the vessels to enter tissues well
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Which immunoglobulin provides the longest-term protection of any antibody class?
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IgG
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What is the half life of IgG?
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21 days
Meaning that a given number of IgG molecules will be reduced by about 50% after 21 days. |
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What is the first and most abundant circulating class produced during the secondary response?
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IgG Class
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Which immunoglobulin provides protection by means of all six mechanisms?
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IgG
neutralization, opsonization, complement activation, immobilization and prevention of adherence, cross-linking and ADCC. |
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Which immunoglobulin is transported across the placenta into the fetus' bloodstream?
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IgG
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Which immunoglobulins protect the newborn?
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Maternal IgG from in utero, IgG and IgA from breast milk.
IgG is in colostrum, IgA is in breast milk after colostrum as well. |
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How long is a newborn protected by maternal antibodies?
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Approximately 6 months
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What is colostrum?
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First breast milk produced after giving birth.
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IgA accounts for ________% of antibodies in the serum.
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10%-13%
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What is the half life of IgM?
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10 days
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What is the half life of IgG?
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21 days
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What is the half life of IgA?
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6 days
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What is the half life of IgD?
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3 days
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What is the half life of IgE?
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2 days
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The most abundant immunoglobulin produced (not just in serum)
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IgA
It's present in mucus. |
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The dimer of this immunoglobulin is found on the mucous membranes.
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IgA
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The secreted form of this immunoglobulin is found in gastrointestinal, genitourinary and respiratory tracts.
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IgA
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This immunoglobulin is found in secretions such as saliva, tears and breast milk.
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IgA
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What mechanisms does IgA utilize to protect the host?
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Neutralization, interfering with attachment of microbes to host cells.
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How and where is IgA produced?
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In the plasma cells located in mucosa-associated lymphoid tissues (MALT).
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How is IgA protected from enzymes on the mucosal surface?
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A polypeptide called the secretory component is attached to IgA as IgA is transported across the mucosa.
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IgD accounts for _______% of immunoglobulin in the serum
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<1%
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Which immunoglobulin's functions are not very well defined?
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IgD
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IgE accounts for ________% of immunoglobulin in the serum
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<0.01%, IgE is barely detectable in blood
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Why is IgE barely detectable in the serum?
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It is the most tightly bound by the FC region to basophils and mast cells rather than being free in circulation.
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Bound _________ allows mast cells and basophils to detect and respond to antigens.
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IgE
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When antigen binds to two adjacent IgE molecules on a mast cell or basophil _______ is released by the mast cell or basophil.
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Histamine and other inflammatory mediators
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_________ - mediated responses are important in eliminating parasites, particularly helminths
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IgE
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_______ and ________ release their chemicals when IgE binds to normally harmless materials such as foods, dust and pollens
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Basophils and mast cells.
this is called hypersensitivity reaction. |
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Pneumonic for the six mechanisms of function of immunoglobulins.
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INOCCA
Immobilization and prevention of adherence Neutralization Opsonization Complement system activation Cross-linking Antibody-dependent cellular cytotoxicity (ADCC) |
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Why is IgM particularly effect at cross-linking antigens?
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It is a pentamer and has 10 linking sites and can link 10 microbes at once.
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Which maternal antibody classes protect a breast-fed newborn?
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IgG and IgA
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In opsonization with IgG, why is it important that phagocytes recognize the antibodies only after they bind antigen?
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Phagocytes could phagocytize just the antibodies before they have attached to anything.
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Does clonal selection pertain to both B cells and T cells?
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Yes
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These lymphocytes have not fully developed their antigen-specific receptors
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Immature lymphocytes
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These lymphocytes have antigen receptors, but have not yet encountered the antigen to which they are programmed to respond
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Naive lymphocytes
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These lymphocytes are able to proliferate; they have bound antigen via their antigen receptor and have received he required accessory signals from another cell, confirming that the antigen merits response
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Activated lymphocyte
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These lymphocytes are descendants of activated lymphocytes, armed with the ability to produce specific cytokines or other protective substances.
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Effector lymphocytes
p. 363 Plasma cells are effector B cells, Tc cells are effector cytotoxic T cells, and TH cells are effector T helper cells. |
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These lymphocytes are long-lived descendants of activated lymphocytes; they can quickly become activated when an antigen is encountered again. They are responsible for the speed and effectiveness of the secondary response.
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Memory lymphocytes
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Describe the clonal selection theory.
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The process by which the binding of an B cell receptor to an antigen activates that B cell and allows it to differentiate into memory B cells and plasma cells which create antibodies for the antigen and release the into the system.
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How does a naive lymphocyte differ from an activated one?
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Naive has never bound antigen. Activated has bound antigen.
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If the heavy chain of an antibody is approx. 450 amino acids long, how much DNA would be required to encode 10^9 separate heavy chain genes?
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3 x 10^9 because an amino acid is 3 a nucleotide sequence
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The process in which a B cell takes in an antigen when it encounters it
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Endocytosis
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What is endocytosis?
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The process by which cells bring molecules into it by engulfing it with cell membrane and pinching it off from the outer environment.
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MHC Class II molecules
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Major-histocompatibility molecules. Proteins on the surface of B cells which bind with peptide fragments of a mo the cell had bound to. They present the mo to Th cells.
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MHC Class I molecules
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Major-histocompatability complex on the surface of cells used to present antigen to cytotoxic T cells
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How do Th cells activate B cells when they recognize an antigen the B cell is presenting?
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By releasing cytokines.
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What is anergic?
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unresponsive to future exposure to the antigen, resulting in tolerance to that antigen.
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What happens if no TH cells recognize the antigen presented by the B cell?
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The B cell becomes anergic to the antigen, meaning it becomes tolerant of it. This is an important process of being tolerant of self and harmless antigens.
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A form of natural selection among proliferating B cells
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Affinity maturation
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What accounts for the change in a B cell's ability to bind antigen?
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Affinity maturation
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All B cells are initially programmed to differentiate into plasma cells that secret ______ immunoglobulin.
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IgM
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If class switching occurs in Peyer's patches, which immunoglobulin will likely be the end result?
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IgA.
Peyer's patches are part of the system in which IgA is most abundant |
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The ___________ response is significantly faster and more effective than the ___________ response
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secondary; primary
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______________ are responsible for the efficiency of the secondary response
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Memory B cells
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___________ can activate B cells without the aid of TH cells
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T-independent antigens
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Affinity maturation and class switching occur in the ________ (primary/secondary) response?
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Primary response
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Do T cells ever produce antibodies?
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No
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What is the difference between a B cell receptor and a T cell receptor (structure)
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B cell receptor is a membrane bound version of the antibodies that B cell is programmed to make. Its structure is identical to the antibodies.
T cell receptor has either alpha/beta or gamma/delta polypeptide chains, each with a variable and a constant region. |
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How do T cell receptors interact with antigen?
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Must be presented by another host cell
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A T cell receptor is similar to which part of a B cell receptor?
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One arm of the B cell receptor
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MHC Class _____ present endogenous antigens and MHC Clsss _____ present exogenous antigens
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I, II
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Describe endogenous and exogenous antigens
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Endogenous antigens are made within the cell (viral particles) and exogenous have been taken up by the cell (B cell)
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What kind of cells produce Class I MHC?
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Nucleated cells
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What kind of cells produce Class II MHC?
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Antigen presenting cells (APC's) such as B cells, macrophages, dendritic cells.
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_______ T cells recognize MHC Class I molecules
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Tc Cells
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_______T cells recognize MHC Class II molecules
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TH cells
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How do scientists distinguish cytotoxic and helper T cells since they are identically microscopically?
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CD Markers
Cluster of differentiation markers which are proteins on the cells. |
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Most cytotoxic T cells have _____ marker.
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CD8
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Most helper T cells have _____ marker.
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CD4
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Which CD marker is a receptor for HIV?
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CD4, which is why helper T cells are the target for HIV
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What is the fate of a cell that presents antigen recognized by a Tc cell?
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The cell will be prompted by cytotoxins released by the Tc cell to undergo apoptosis.
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What is the fate of a cell that presents antigen recognized by a TH cell?
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The presenting cell will become activated and multiply.
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The scouts of innate immunity
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Dendritic cells
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______ cells play a crucial role in T cell activation
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Dendritic cells
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How do dendritic cells gather material from the respiratory tract and the lumen of the intestine?
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By sending tentacle-like extensions between the epithelial cells of the barriers.
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What kind of receptors do dendritic cells have?
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Toll like receptors and others
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What does a dendritic cell do after it recognizes a pathogen?
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Travels to the secondary lymphoid organs where it will encounter naive T cells
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What kind of cells do dendritic cells interact with in the secondary lymphoid tissues?
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Naive T cells
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Dendritic cells are naive until they mature when?
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En route to the secondary lymphoid organs.
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Dendritic cells that detected pathogens produce surface proteins called __________.
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Co-stimulatory molecules
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What two things must be present for a naive T cell to become activated?
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Antigen recognition and the dendritic cell must be presenting co-stimulatory molecules.
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What happens to a naive T call that recognizes antigen being displayed by dendritic cells but there are no co-stimulatory molecules present?
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The naive T cell becomes anergic, which means it has a tolerance to that antigen. The antigen could be a self antigen or is simply just not harmful. The t cell will eventually undergo apoptosis.
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What kind of molecules (class I or class II) do dendritic cells present peptides on?
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Both class I and class II, called cross presentation
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What is meant by "cross present"
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The ability of a (dendritic) cell to present peptide on both class I and class II MHC molecules
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Cross presentation by dendritic cells allows activation of which type of T cell?
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Both cytotoxic T cells and helper T cells.
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Tc Cells expose target cells to these two things in order to initiate target cell apoptosis?
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Perforin (a molecule that forms pores in the cell membrane) and several proteases (cause reactions from within the cell which trigger apoptosis)
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What is perforin?
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A cytotoxin which forms pores in a cell membrane, particularly a cell targeted by a Tc cell for apoptosis.
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What is a death receptor?
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A receptor on a self cell which can be engaged by a specific molecule on Tc Cells to initiate self cell apoptosis.
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Why is it more beneficial to kill a target cell by means of apoptosis rather than cell lysis?
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It minimizes the number of intracellular microbes that might spill into the surrounding area and infect other cells.
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Does a Tc cell die after it affects a target self cell?
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No, it can go on to kill other targets.
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What are the functions of two cytokines released into the environment after a Tc cell initiates apoptosis of an infected self cell?
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One cytokine stimulates antigen processing and presentation in neighboring cells, causing them to present more antigen on their surfaces which makes it easier for other Tc cells to find them and see if they were also infected.
Another cytokine activates local macrophages whose TLR's have been triggered. Macrophages will come phagocytize the dead self cell. |
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_______ cells orchestrate the immune response
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TH cells
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How do TH cells orchestrate the immune response?
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They activate B cells and macrophages, and direct the activity of B cells, macrophages and T cells.
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Describe how a conjugate vaccine works and why it is needed.
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Ie meningitis in small children
Meningitis is surrounded by a capsule made of a polypeptide chain, which is a T-independent antigen. Small children do not deal with T-independent antigens so by covalently attaching a large protein to the meningitis molecule. the polysaccharide component binds to a B cell receptor and the entire molecule is taken in. Because the B cell will present some of the protein component, the TH cells will recognize it and induce a better immune response. |
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A molecule that binds B cell receptor yet does not normally elicit antibody production
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Hapten
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Why would TH cells activate macrophages?
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If the macrophage can't control an invader by phagocytosis, a TH cell can activate it, allowing it to produce more potent destructive mechanisms.
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What physical changes does a macrophage undergo once it is activated?
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It becomes larger, the plasma membrane becomes ruffled and irregular, and the cell increases its metabolism so lysosomes increase in number, produces nitric oxide.
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If activated macrophage response is still not sufficient, macrophages fuse together to form ________.
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Giant cells
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What are giant cells?
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Macrophages fused together that work with other macrophages and T cells and form granulomas that wall off the offending agent, preventing offending microbes from escaping and infecting other cells.
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What kind of organism can survive within a macrophage?
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Tuberculosis
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If tuberculosis survives phagocytosis, what is the back up plan?
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TH cells activate the macrophage to release more potent reactions.
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Name three types of antigen-presenting cells.
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B cells, macrophages and dendritic cells
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If an effector CD8 cell recognizes antigen presented on an MHC class I molecule, how should it respond?
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By releasing cytokines which induce cell apoptosis, as well as cytokines which increase antigen recognition and presentation in neighboring cells.
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Why would a person who has AIDS be more susceptible to the bacterium that causes tuberculosis?
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TH cells are invaded and killed by the AIDS virus, and TH cells are required when a macrophage attempts and fails to phagocytize tuberculosis because the tuberculosis is not degraded by phagocytosis. In this case a TH cell would activate the macrophage allowing it to produce more powerful means to kill the tuberculosis.
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What is the mechanism used by Natural Killer cells to kill antibody-bound cells?
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Antibody-dependent cellular toxicity
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Some viruses have adapted to prevent a cell from producing MHC Class I molecules. How are these cells managed?
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Natural killer cells recognize a cell's lack of MHC Class I molecules on its surface along with other signals that the cell is under stress, and initiate apoptosis.
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Why would a self cell not display a MHC Class I molecule?
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A virus may have adapted to prevent the cell from producing MHC Class I molecules in an effort to prevent Tc Cells from initiating apoptosis on the cell.
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Why might a virus encode its own version of an MHC Class I molecule?
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Because at least there will be some version of the MHC molecule on the cell surface which would trick the natural killer cells into not initiating apoptosis due to the cell's lack of MHC Class I surface molecules.
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