| Term | Definition |
|---|
| Antigen that induces tolerance or unresponsiveness | Tolerogen |
| autoimmune disease | What happens when tolerance mechanisms fail? |
| B - bone marrow T - thymus | Where does central tolerance occur for B and T cells? |
| self antigens only | What types of antigens are expressed in the generative lymphoid organs? |
| If T-cell receptors bind to MHC molecules at all they are positively selected | What is positive selection? |
| T-cells that bind too strongly to self-MHC die | What is negative selection? |
| B-cells that bind too strongly have another chance to rearrange the L chain of the receptor and undergo peripheral tolerance before dying | What is the difference between T and B cell central tolerance? |
| Molecule expressed by T-cells that causes it to undergo anergy if poor response | What is CTLA-4? |
| No expression of co-stimulator molecules | What do APC's do to prevent T-cells from living? |
| repeated activation by self ag, signaling through CD25 (absent) by IL-2 (growth), and lack of costimulatory molecules producing pro-apoptotic proteins | What are three ways that apoptosis is activated in T-cell tolerance? |
| Normally Bcl-2/Bcl-X inhibit the Bax/Bak channel; BH3, a proapoptotic signal inhibits Bcl-2/Bcl-X from clogging the channel = cell pore formation; also activation of caspases | How does apoptosis occur in T-cells? |
| if they respond to self-ag they undergo anergy via decrease in CXCR5 (can't get into follicle) | How do B-cells undergo peripheral tolerance? |
| 1. Fas-FasL signals from Th cells; 2. lack of anti-apoptotic factors which are found normally in the follicle | What are the two mechanisms of B-cell apoptosis? |
| CD-25 | What do Treg cells constitutively express? |
| IL-2Ra | What is the CD-25 molecule? |
| MHC class II | What are most autoimmune diseases associated with? |
| 1. APC is activated by a microbe and then accidentally activates a self-reactive T cell; 2. molecular mimicry-APC presents a microbe that resembles a self AG to a T-cell who then thinks self tissues are foreign because they look so similar | What are the two ways that T-cells can become activated due to environmental stimuli? |
| IL-10 or TGF-B | What do Treg cells secrete to suppress self-reactive cells? |
| Their TCR has a lower threshold for signaling than regular T cells | T-reg cells can be activated by self-Ag because? |
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