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12 Cards in this Set
- Front
- Back
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Describe structure of TCR.
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2 chains (alpha/beta 90% or gamma/delta in mucosa) held together by S-S bond. Variable & constant region. Transmembrane cytoplamic tail
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How are TCR like Ig.
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Undergo recombination & allelic exclusion
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Describe TCR recombination.
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In the thymus, VDJ genes rearrange to form the beta chain V region & V & J genes rearrange to form the alpha region. Allelic exclusion guarantees only 1 alpha & beta expressed per cell. Jcnal diversity. Cregions expressed randomly
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What is a major diff b/w TCR & Ig?
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In their specificities: Ig can bind a wide array of Ag but TCR are restricted in the specificities (must be bound to MHC)
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What is (+) selection?
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During T-cell maturation , T-cells that bind self Ag on thymic dendritic cells are killed
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Describe the endocytic pathway.
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APC phago Ag-> lysosome + phagosome->digest. Mean while, MHC-II assembled in ER are bound by Ii chain to block Ag-> exocytosedfrom golgi. MHC-II vesicle + phagolysosome fuse-> Ii released-> Ag binds-> exocytosed to cell membrane
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Describe cytosolic pathway.
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Virus (via ubiquitine) degraded by proteosome-> TAP transports to ER. Mean while, MHC-I assembled in ER are bound by calnexin to stabilize. Ag binds MHC-I-> exocytosed to celll surface
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What are the accessory molec for TCR?
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CD3, CD28, CD40L
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What are the receptors on APC for CD28 & CD40L
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CD28 bind B7 on dendritic cells. CD40 L binds CD 40 on macro or B-cells
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What are the charac of CD3?
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3 glycoprotein chains. Assoc w/ TCR in ER and then adds zeta homodimer in golgi
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Describe the 1st step in the signal transduction pathway for TCR?
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Needs 2 signals. 1) CD8 or CD4 binds MHCI or MHCII (+CD3)-> Ca release & DNA binding factors.
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Describe the 2nd step in the signal transduction pathway for TCR?
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2) CD28 or CD40L bind B7 or CD40-> stabilize mRNA, secretes IL-2 that binds IL-2 receptor-> JAK/STAT-> cell prolif
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