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21 Cards in this Set
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- Back
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The success of tissue and organ transplants depends on what?
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The donors and recipients HLA(human leukocyte antigen) encoded by HLA genes.
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Are these proteins alloantigens?
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Yes. They differ among members of the same species.
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If the HLA proteins differ on the donors cells from those of the recipients, an immune response occurs. TRUE/FALSE
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TRUE.
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The genes for the HLA proteins are found where?
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They are clustered on the MHC, located on the short arm of chromosome 6.
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Genes HLA-A, B and C code for what?
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They code for class 1 MHC proteins.
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Each person has 2 haplotypes. TRUE/FALSE
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TRUE. Two sets of these genes, one on the paternal and the other on the maternal chromosome 6. These genes are diverse and polymorphic. No one can make more than two class 1 and 11 proteins at each locus. Expression is codominant..
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Are minor antigens created at any time?
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Yes. In addition to the major antigens encoded by HLA genes, there are an unknown number of minor antigens encoded by genes at sites other than the HLA locus.
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Can these minor genes cause harm?
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They can induce a weak immune response that can result in slow rejection of a graft. They are allelic variants.
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Is there a class 111?
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Between class 1 and 11 gene loci is a third locus, sometimes called class 111.This locus has several immunologically important genes encoding 2 cytokines, TNF(tumor necrosis factoe, and lymphotoxin) and 2 complement components, C2 and C4.
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Where are class 1 MHC proteins found?
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On the surface of virtually all nucleated cells.
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How many proteins are encoded by the allelic genes?
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App. 20 at the A locus, 40 at the B, and app. 8 at the C.
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The complete class 1 protein is composed of what?
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A 45,000 molecular weight heavy chain nonconvalently bound to a B2 microglobulin.
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The polymorphism of these molecules is important in the recognition of self and non-self. TRUE/FALSE
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TRUE.
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What are class 11 MHC proteins?
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These are glycoproteins found on the surface of certain cells, including macrophages, B cells and dendritic cells of the spleen, and Langherhan cells of the skin.
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What are they composed of?
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Two polypeptides, MW 33,000 and 28,000 that are noncovalently bound. The two peptides also have a constant region where the CD4 proteins of the helper T cells bind.
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The ability of T cells to recognize antigen is dependent on what?
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It is dependent on the association of the antigen with either class 1 or class 11 proteins.
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Give an example of the above statement.
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Cytotoxic T cells respond to antigen in association with class 1 MHC protein. A cytotoxic T cell, that kills a virus infected cell, will not kill a cell infected with the same virus if the cell does not also express the appropriate class 1 proteins.
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Helper cell activity depends on what?
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Depends on both the recognition of the antigen on APCs and on the presence on these cells of self class 11 MHC proteins
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What is MHC restriction?
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The requirement to recognize antigen in association with a self MHC protein.
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When do T cells recognize antigens?
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Only when the antigens are presented on the surface of cells(in association with either class 1 or 11 MHC proteins), whereas B cells do not have that requirement and can recognize soluble antigens in plasma with their surface monomer IgM acting as the antigen receptor.
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MHC genes and proteins are important in 2 medical contexts. What are they?
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1. Many autoimmune diseases occur in people who carry certain MHC genes.
2. Success of organ transplants is in large part, determined by the compatibility of the MHC genes of the donor and recipienr. |
