1. Positive selection: selection for self-MHC 2. Negative selection: selection against those having receptors recognizing self-antigens
What is immature T cell called?
MHC restriction is:
AKA self-MHC restriction, the ability of T cells to recognize only our own MHC molecules
2 types of TCRs
1. αβ TCR - consists of 1 α chain and 1 β chain . More numerous and diverse 2. γδ TCR - consists of 1 γ chain and 1 δ chain . Interact with non-classical MHC molecules . Found in specific tissues (peripheral lymphoid, epithelial cells, intestines, etc.)
Components of pre-TCR
β chain, CD3 and ζ chains
First signal of T cell activation
via CD3 complex, TCR recognizes and engages its MHC-peptide complex
Second signal of T cell activation
Interaction between CD80/CD86 on APC and CD28 on T cell or IL-1 secreted by APC
Previously activated T cell needs 1 or 2 signals?
Once a T cell has been previously activated, only the 1st signal is required to stimulate the T cell again
Which chain does not follow rule of allelic exclusion?
α chain (it's possible to have one T cell with two different TCRs, same β chain but different α chains)
2 ways to generate antigen-independent diversity of TCR genes
1. Combinatorial diversity - any V with any D with any J, etc. 2. Junctional diversity - P-nucleotide addition, etc.
Which TCR is double negative?
Components of full TCR complex
αβ TCR, CD3, 2 ζ chains
Which domain of MHC class II does CD4 interact with?
Which domain of MHC class I does CD8 interact with?
α2 & α3
Exceptions of TCR gene rearrangement
. β and δ chains can skip D gene/have multiple D genes . α chain does not follow allelic exclusion
Functions of CD3
. With ζ chains, CD3 chaperons successfully rearranged β chain to surface . Provides biophysical means for signal transduction to activate T cell
What does activated T cell express on surface?
What does activated T cell secret?
What does interaction of IL-2R and IL-2 result in?
Further proliferation and differentiation of the activated T cells
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