Lecture # 10 Comparison of B Cell and T cell Antigen Receptors MHC structure/function

Question 1

T Cell Receptors recognize and bind to

Answer 1

Peptide antigen bound withing MHC proteins.

Question 2

In the steady state or a non infectious situation, MHC class I molecules are transported to the surface:

Answer 2

with self peptide bound

Question 3

Are CD4+/CD8+ T cell receptors?

Answer 3

No. CD4+ and CD8+ are co-receptors on the surface of T cells.

Question 4

What is the difference between antigen recognition in T cells and B cells?

Answer 4

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.

Question 5

Effect of CD4+ and CD8+

Answer 5

CD4+ activate macrophages to kill phagocytosed microbes; CD8+ kill infected cells

Question 6

Do TCRs bind to peptide fragments directly?

Answer 6

NO!!! TCR responds to short amino acid sequences, contiguous, internal, need to be unfolded and processed.

Question 7

What are the difference between epitope recognition in B Cells and T Cells?

Answer 7

B Cells recognize epitopes displayed on the surface of antigens, while T cells recognize peptide fragments of antigens (often are buried)

Question 8

Which HLA class binds larger peptide fragments?

Answer 8

Class II binds larger fragments, smaller fragments for MHC I

Question 9

MHC I Binding character

Answer 9

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.

Question 10

MHC II binding characteristics

Answer 10

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

Question 11

Which MHC is correlated to CD8+? CD4+?

Answer 11

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

Question 12

What types of cells express Class I MHC? Class II MHC?

Answer 12

Class I CD8+ is present on all nucleated cells ( looking for intracellularly infected cells); Class II CD4+ are present on APCs DCs, macrophages, phagocytes. CD4+ increases the pathogenic nature of DCs, macrophages etc.