Final T-cell receptor Flashcards
What is the structures of TCR’s?
- membrane bound heterodimer of either a and b chains or y and delta chains
- two chains held together by a disulphide linkage
- each chain has a transmembrane domain and a cytoplasmic tail
What is on the transmembrane region?
It is rich with positively charged amino acids
What is TCR antigen recognition mediated by?
The V domain of both peptide chains
What is the antigen contacted by?
Three hyper variable loops designated CDR 1-3
Besides the 3 CDR’s what else contributes to antigen recognition
Hypervariable loop 4 (HV4)
When can TCR recognize antigens
- TCR can only recognize antigens when presented with the correct MHC
- the TCR simultaneously contacts both the peptide and the MHC molecule
What is self restriction?
Self restriction is the result of a need for the TCR to properly engage the MHC molecule in addition to the specific peptide
How is the self restriction generated?
Through the positive and negative selection of immature T-lymphocytes in the thymus
Is the TCR’s cytoplasmic tail capable of signalling
No, it can’t signal
What is antigen signalling in T cells facilitated by?
Accessory molecules CD3
What are the CD3 chains?
Trans-membrane proteins with ITAM motifs on their cytoplasmic tails
What are the co-markers CD4+ and CD8+ used for
- used to distinguish helper cells from cytotoxic cells
- bind the invariant regions of the MHC molecules
- CD4-MHC2
- CD8-MHC1
For diversity, what does each TCR gene family contain?
- several variable gene segments (V)
- several joining gene segments (J)
- 1 or 2 constant gene segments (C)
Explain TCR gene rearrangement
- beta rearranges first
- expressed on the cell surface with a Pre-T alpha chain
- successful arrangement of TCR b will then allow the thymocyte rearrange its TCR a chain
What is retried to mediate the initial recombination signal sequences (RSS) recognition and DNA cleavage?
The products of the recombination activating genes 1 and 2
