Chapter 9 T-cell Receptor Dr. Capers. Kuby IMMUNOLOGY Sixth Edition Chapter 9 T-Cell Receptor...
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Transcript of Chapter 9 T-cell Receptor Dr. Capers. Kuby IMMUNOLOGY Sixth Edition Chapter 9 T-Cell Receptor...
Chapter 9
T-cell Receptor
Dr. Capers
Kuby IMMUNOLOGYSixth Edition
Chapter 9T-Cell Receptor
Copyright © 2007 by W. H. Freeman and Company
Kindt • Goldsby • Osborne
T cell receptor vs B cell receptor T cell receptor is only membrane bound
○ Doesn’t appear in soluble form like antibodies so more difficult to assess it’s structure
Antigen binding of T cell receptor is weaker than that of antibodies
Antigen recognized by T cells is not antigen alone but antigen associated with MHC molecules
(a) T cell receptor (TCR) is specific for peptide A
(b) Right MHC haplotype but wrong antigen (peptide B)
(c) Right antigen (peptide A) but wrong haplotype
T cell receptor (TCRs)○ TCR heterodimers are similar to
immunoglobulinsTherefore they are classified in immunoglobulin
superfamilyResembles Fab fragment
TCRs○ Associate with MHC – αβ TCR○ Do not associate with MHC – γδ TCR
- Much remains to be learned of function of γδ TCR
Rearrangement of TCR genes Similar to that of Ig
Rearrangement of α and γ chains○ V, J, and C segments
Rearrangement of β and δ chains○ V, D, J, and C segments
Generation of TCR diversity (a lot like Ig)○ Multiple germ-line gene segments○ Combinatorial V-(D)-J joining○ Junctional flexibility○ P-region nucleotide addition○ N-region nucleotide addition○ Combinatorial association of light and heavy
chains However, there is no somatic mutation with
TCR○ May be to ensure that after thymic selection, the
TCR doesn’t change to cause self-reactive T cell
TCR-CD3 Complex Accessory
molecules help in signal transduction after interaction of T cell with antigen2 Zeta ζζ chainsHeterodimer of delta
epsilon γε chainsHeterodimer of
delta epsilon εδ chains
T cell accessory molecules T cells can be divided into 2
populations:○ CD4+
Recognize antigen associated with Class II MHC OR
○ CD8+Recognize antigen associated with Class I
MHC
○ CD4 and CD8 function as coreceptors and assist with signal transduction
Affinity of TCR for peptide-MHC complexes is enhanced by coreceptors
Allogenic – genetically different individuals of same species
Alloreactivity of T cells is puzzling:○ Evidence supports that T cells can only
respond to antigen+MHC○ However, T cells can recognize a foreign MHC
molecule alone- As with transplants