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26 Cards in this Set
- Front
- Back
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What is tolerance?
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- failure to respond to self antigens
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what happens when cells fail to induce tolerance?
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- autoimmune disease
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What are features of Ags that induce tolerance?
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- Ags on tissue
- present in thymus/bone marrow - are not present with secondary signals - long lived Ag may induce prolonged TCR engagement |
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What are features of Ags that induce immunogenicity?
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- Ag on a microbe
- concentrated in peripheral lymphoid organs - present with secondary signals - short lived and is eliminated by immune system |
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What are 2 consequences of tolerance?
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- anergy
- apoptosis |
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What is the consequence of ignorance?
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- no response to nonimmunnogenic Ag
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What is central tolerance?
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- immature lymphocytes encounter self-Ag in thymus/bone marrow
- if cell reacts too strongly to self-Ag targeted for apoptosis OR B cells: receptor editing T cells: reprogramming to regulatory T cells |
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What is peripheral tolerance?
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- mature lymphocytes that are unresponsive to self Ags
- 3 outcomes 1) inactive/anergic 2) overactive and deleted 3) suppressed by regulatory T cellsed |
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What does B7 bind to on the T cell when self Ag is presented?
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- CTLA-4, an inhibitory receptor
- anergic T cell |
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How does deletion occur when T cells fail peripheral tolerance?
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- Without 2nd signal of IL-2, pro-apoptotic proteins outweigh the number of anti-apoptotic proteins
- death receptor ligand binds to death receptor to initiate apoptosis |
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Tregs are a subpopulation of what type of T cell?
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- CD4
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What molecules are on Tregs that are not on other T cells?
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- High levels of CD25 (increases affinity of IL-2R b/c cell cannot make its own IL-2)
- FOXP3 (TF required for dvp and function to promote immunosuppresent molecules and inhibit effector molecules) |
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What do Tregs inhibit?
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- T cell activation
- T cell effector functions |
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How is central tolerance broken?
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- mature lymphocytes encounter a self-Ag in periphery that have not been exposed to
- Tregs do not develop/function |
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What is Autoimmune Regulator (AIRE)?
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- TF that exposes lymphocytes to some tissue specific Ags
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What are 3 factors that contribute to autoimmunity?
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1) Genetics (MHC genes often involved)
2) infections (molecular mimicry) 3) hormonal (higher in females) |
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What does Foxp3 mutations cause?
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- early death b/c Tregs are designed to regulate autoimmunity
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What happens if there is a defect in the Fas/FasL genes?
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- not able to destroy self reactive lymphocytes
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What happens if there is a mutation in IL-2 or IL-2R
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- deficiency of regulatory T cells
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What is the target of Myasthenia gravis?
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- ACH receptor
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What is the target of Grave's disease?
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- Thyroid stimulating hormone receptor
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What is the target of pernicious anemia?
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-intrinsic factor of gastric parietal cells
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What is the target of Type I diabetes?
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- Beta cells (pancreatic islet Ag)
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What is the target of rheumatoid arthritis?
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- Ag in joints
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What are current methods to treat autoimmune diseases?
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- immunosuppressive drugs (cortisone)
- anti-inflammatory - plasmapheresis (removes self-reactive cells and replace w normal) - palliative |
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what are potential methods to treat autoimmune diseases?
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- Biotherapeautics (use Ab/cytokines to neutralize only defective part of immune)
- Self-Therapy with Tregs (isolate patient's Tregs, grow in lab, inject back in) |
