T-cell Receptor Flashcards
What is a TCR?
It is a membrane-bound heterodimer of either alpha or beta chains or gamma and delta chains
How are the two chains held together?
Disulphide linkage
What does each chain posses?
A transmembrane domain and a short cytoplasmic tail
What is the transmembrane region rich in? What does this allow for?
It is rich in positive amino acids which allows the association of other molecules
How is TCR Ag recognition mediated?
By the V domain of both peptide chains
What does the Ag contact on the TCR?
3 hypervariable loops (CDR1-3)
In addition to the 3CDR regions, what stabilizes the structure?
Hypervariable loop 4 (HV4) contributes to Ag recog. and stabilizes structure
What must occur for the TCR to recognize Ag?
The Ag has to be presented in the context of the correct MHC
What does the TCR contact?
The Ag and MHC
What influences the TCR recognizing AG?
The surface of the MHC
Why do some vaccines not work?
Some ppl don’t have the right MHC so the TCR can’t see the Ag
What is the result of a TCR unable to engage the MHC?
Failure to recognize the bound Ag
How are self restricted TCR generated?
Positive and negative selection of immature T-lymphocytes in the thymus
What do my immature T cells see?
Everyone’s MHC
What do my mature T cells see?
Only my MHC
Why can a TCR not mediate intracellular signaling?
It has a short cytoplasmic tail
How is Ag signaling facilitated in TCR?
By accessory molecules CD3
What is CD3?
What does it do?
Transmembrane proteins with ITAM motifs on their cytoplasmic tails
The accessory molecule that mediates intracellular signaling in TCR
What does CD3 have that allows it to cluster w/ TCR?
It has negatively charged residues in the transmembrane domain
What are TCR co-receptors?
CD4 and CD8
Where do co-receptors bind?
The invariant regions of the MHC molecules
CD4 goes with which MHC class?
MHC class 2 (Killer)
CD8 goes with which MHC class?
MHC class 1 (Helper)
What increases the sensitivity to the Ag?
The co-receptors CD4 and CD8
