Flashcards in Regulation of the Immune System- L11 Deck (14):
1
Tolerance
Lack of response to a specific antigen
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2 major mechanisms of tolerance induction
1. Deletion of reactive cells
2. Inactivation of reactive cells: Anergy
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Clonal deletion in T cells
-Occurs in thymus
-Tight association of autoreactive TCR to MHC presented antigen on thymic dendritic cells causes apoptosis
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Clonal anergy in T cells
T cells become inactivated if an appropriate co-stimulatory signal is not received
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Generation of T regs
Active process, suppresses autoreactivity
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Mechanisms of tolerance in T cells
1. Clonal deletion
2. Clonal anergy
3. Functional deletion
4. Generation of suppressor or T reg cells
5. Blocking of presentation or activation
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Mechanisms of tolerance in B cells
1. Clonal deletion
2. Clonal abortion/clonal anergy
3. Functional deletion
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T regs
FoxP3+CD25+CD4+T cells that actively suppress pathological and physiological immune responses
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IPEX
Syndrome where FoxP3 is lost and T regs cannot differentiate. Patients with IPEX develop many autoimmune disorders.
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Mechanisms of regulation by T regs
-Direct contact with target cells
-Cytokine mediated suppression of T cells
-Cytokine mediated suppression of pAPC function
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B7:CTLA4
Stop signal for T cells, binding inactivates them
CTLA4 expressed by T cells, B7 by APCs.
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Protein antigens can induce
-Humoral immunity
-Cell mediated immunity
-Class switching
-Affinity maturation
-Generation of memory cells
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Polysaccharide and lipid antigens can induce
-Humoral immmunity
-Can NOT induce CMI
-This is why we don't have long-lived immunity to encapsulated bacteria!!!!
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