Flashcards in Lecture # 10 Comparison of B Cell and T cell Antigen Receptors MHC structure/function Deck (12):
T Cell Receptors recognize and bind to
Peptide antigen bound withing MHC proteins.
In the steady state or a non infectious situation, MHC class I molecules are transported to the surface:
with self peptide bound
Are CD4+/CD8+ T cell receptors?
No. CD4+ and CD8+ are co-receptors on the surface of T cells.
What is the difference between antigen recognition in T cells and B cells?
T cells must recognize antigens in the context of MHC of a cell, whereas B cells are more independent and recognize pathogens in extracellular spaces.
Effect of CD4+ and CD8+
CD4+ activate macrophages to kill phagocytosed microbes; CD8+ kill infected cells
Do TCRs bind to peptide fragments directly?
NO!!! TCR responds to short amino acid sequences, contiguous, internal, need to be unfolded and processed.
What are the difference between epitope recognition in B Cells and T Cells?
B Cells recognize epitopes displayed on the surface of antigens, while T cells recognize peptide fragments of antigens (often are buried)
Which HLA class binds larger peptide fragments?
Class II binds larger fragments, smaller fragments for MHC I
MHC I Binding character
8-10 peptides, anchor residues ( aas at the end of the peptide) bind tightly to the MHC cleft. Class I only two binding residues; Class MHC binding groove is more closed.
MHC II binding characteristics
usually 12-16 aa, but can be upwards of 30+. Anchor residues are in the middle of; anchor residues lie within the peptide length away from the ends. Class II has four anchor residues; binding groove is more open
Which MHC is correlated to CD8+? CD4+?
CD8+ binds to MHC I, CD4+ binds to MHC II; CD8+ and CD4+ are both co receptors that bind to non polymorphic regions on MHC