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9 Cards in this Set
- Front
- Back
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where do T cells come from, where do they go first, and what's the major thing they get when they arrive?
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start out in the bone marrow, but have to move to the thymus to get their T-cell receptors (TCR) and become mature. Note th
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what do the T cells do in the thymus, generally, and when are they allowed to leave?
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3 parts:
Migrate to it, then proliferate inside it. Most will be selected against here. Differentiate - Get their TCR, their CD3, and then select to become CD4 or CD8 cells. They also have Positive and Negative selection: Positive means that they bind (but not too much) self-MHC molecules. They're given a survival signal if they can bind self-MHC. Negative means that they react with self antigens, and this is bad. They're inactivated (if half-binding) or killed off (if super binding). |
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in the THYMUS, where do most of the cells live? what are the layers?
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the cortex has most of the T cells. Lower down, in the medulla, has fewer cells but more APC's from the bone and macrophages.
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what are the forms that a TCR comes in
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alpha beta is >95% and the one we should know.
Gamma delta is the other. Just know it exists. |
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CD4, CD8, etc -how do cells start out, and how do they end up?
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Start out as dual negative, then as dual positive - then during positive seleciton, you eliminate one and are left with being positive in only one.
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what are the chemicals that the T cell encounters in the thymus?
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thymosin, thymopoetin, and thymulin - these are all about making it build a TCR.
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how do you become a CD4 or Cd8 cell?
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this depends on what kind of MHC you're presented with.
If you get an MHC class II, you become a CD4 cell. If it's MHC class I, you become CD8. Note that this is called positive selection. If you bind super tight or too weakly, you're apoptosed. Need to bind to self MHC just the right amount. This gives you your survival signal. |
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what's negative selection and where does it happen? what cells do it?
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any T cell that bind something self (that's self MHC) is eliminated
remember that less than 5% of T-cells ever make it out of the thymus. to do this test, you need cells that can release self antigen. these include macrophages and medullary epithelial cells. this happens as they descend from the cortex into the medulla. |
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what's CD3 and what does it do?
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It's found on all peripheral T cells.
Without it, you can't be a proper T cell. Signaling is perceived by the T-cell receptor, but the signal is transduced by CD3 into the cell. CD3 plus the TCR is called the antigen recognition unit. Note that CD4 and CD8 are about stabilization of the interaction of MHC and T cell. |
