T cell development Flashcards
95% of T-cells have _/5% have _
αβ-chains/γδ-chains
CD3
Associates with TCR, contains ITAMS
TCR simultanously binds two things. Which?
MHC and peptide
TCR co-receptors
CD4 and CD8. Strengthen binding to MHC and carries Lck for ITAM phosphorylation
CD8 cells can bind
MHCI on all cells
CD4 cells can bind
MHCII on immune cells, APCs
T cell devolpment hapens in
The thymus
Four stages of T cell maturation
Stage 1: Stem cells arrive in the thymus, stage 2: diverse TCRs are generated by germline DNA rearrangement, stage 3: Positive selection of T cells capable of somewhat binding peptides on MHC, stage 4: negative selection of T-cell that binds too strong to self-antigen.
β chain rearrangement steps
DJ-joining, V-DJ joining
γδ-chain rearrangement
Happens as a race; if they make a useful receptor before β or α chain is made, the T cell becomes a γδ T cell.
β chain is tested how
By pairing with a surrogate protein and forming of pre-T cell receptor. If superdimer is made by pre-TCR, CD3 clustering sends a signal to pause rearrangement, proliferate and express CD4 and CD8
Double positive
T cell that expresses CD4 and CD8
Junctional diversity
Is generated in both α and β chain.
P-nucleotides
From palindromic sequences in junction
N-nucleotides
From random nucleotide addition by TdT
Positive selection
Binding of MHCI or II on epithelial cells in thymus causes survival and CD4/8 determination in T cells
Failure to bind MHCI or II results in
Continued α chain rearrangements, made possible by lots of V and J segments.
Negative selection
Too tight binding to MHC on dendritic cells and macrophages in thymus causes apoptosis.
Natural Treg cells
Tight but not too tight programs T cells to become immunosupressive - peripheral tolerance.
