Lecture 11 - TCR Flashcards
What are T cell receptors?
Membrane-bound Ig-like molecule expressed on T cells
What affinity do TCRs bind with?
Low affinity
TCR binding affinity vs antibody
TCR - 3-30x10^-6 M binding Antibody - 10^-9 - 10^-12 M binding
TCR structure 1) 2) 3) 4) 5) 6)
1) Two chains: alpha and beta chain 2) Each chain made up of a constant region and a variable region 3) Variable region is on top 4) Disulphide link between alpha and beta chains below C region 5) Charged regions in plasma membrane 6) No signalling motifs in cytoplasmic reigon
Is the proteosome a specific immune system protein?
No Highly conserved, from bacteria, so not initially required for antigen processing
How does TCR send an effector signal?
Recruits CD3, which includes ITAM
What is ITAM?
Immunoreceptor Tyrosine-based Activation Motif Involved in TCR and BCR signal transduction
What makes up CD3?
Gamma, delta, epsilon, zeta chains
Where is ITAM found?
Cytoplasmic region of CD3, Igalpha/Igbeta BCR cytoplasmic region
What is a gamma/delta TCR?
Uncommon type of TCR Cells expressing gamma/delta instead of alpha/beta TCR are often CD4-, CD8-. Function not known
Do T cell specificities change during the immune response?
No. No equivalent of somatic hypermutation
Which TCR chain has V, D and J regions?
Beta
Which TCR region has V and J regions?
Alpha
Difference between T cell genomes and other cells
In T cell genomes, TCR alpha and beta chain loci have undergone somatic rearrangement In other cells, these are in germline configuraiton
How do T cell alpha and beta chains undergo somatic rearrangement?
With heptamer/nonamer RSS, 12/23 rule, V(D)J recombinase complex With allelic exclusion
Rough guide to where CDRs bind to MHC/antigen complex
