T cell recognition Flashcards
TCR
T cell receptor
What is a TCR made up of?
Alpha-beta heterodimer (small proportion have gamma-delta)
What does a TCR recognise?
Antigen complex of antigen peptide fragment with self MHC molecule
Do T cells have CDRs?
Yes
How are the alpha and gamma chains organised?
Rearrangement of V and J segments + C segment
How are the beta and gamma chains organised?
Rearrangement of the V, D, and J segments + C segment
What catalyses the V-J and V-D-J joining?
RAG-1/2 recombinase enzyme
What is the major difference between Ig and TCR genes?
No somatic mutation in TCR genes
What is the TCR complex made up of?
Antigen recognition proteins and invariant signalling proteins
How long is the cytoplasmic tail of TCRs?
3 amino acids (too short to signal)
How does TCR signalling occur?
Clustering with CD3 and recruiting protein kinases to CD3 cytoplasmic tails
What is CD3 composed of?
3 dimers
What are the 2 main groups of T cells
CD4+ or CD8+
What do CDs bind to?
Conserved regions of MHC molecules
What is the role of MHC molecules?
Present antigen to T cell
What does CD4 recognise?
MHC class II
What does CD8 recognise?
MHC class I
What is an example of co-stimulatory molecule?
B7.1 and B7.2 (CD80 and CD86) on APCs
What do co-stimulatory molecules do?
Bind to CD28 on T cells (activatory) - induces IL-2 expression
What is CTLA-4?
Inhibitory receptor for B7 molecules
What is the effect of the co-stimulatory signal alone?
No effect on T cell (both signals needed - costimulatory and specific signal alone)
What happens when T cells are activated?
Develop into effector T cells - helper or cytotoxic
What do Th cells do?
Travel around providing help to B cells and Tc cells. Can activate macrophage or B cell
What is the difference in CD4+ T cells?
Activated and developed in different cytokine environments
What does CTL stand for?
Cytotoxic T lymphocytes
What controls the strength of the CTL response?
Th cells - need exogenous IL-2 to replicate
What is needed to generate memory CTLs
Th cells
What are gamma-delta T cells
Mostly CD4-/CD8- or CD8+
Where are gamma-delta T cells found and what do they recognise
Mainly mucosal tissues. Recognise peptide and non-peptide antigens
Do gamma-delta T cells require MHC?
No
What is the minor (
CD1
What does CD1 recognise
Lipid, glycolipid and other hydrophobic antigens
How are CD1 antigens presented?
By non-polymorphic CD-1 proteins
