Test 3: MHC molecules

Question 1

What peptides are displayed by Class I MHC molecules?

Answer 1

short fragments (8-11 aa’s) that come from endogenous, cellular proteins

Question 2

What are the 3 alleles for MHC I molecules and how many different molecules are displayed?

Answer 2

• HLA-A B and C

- co-dominant expression=6 different molecules on each nucleated cell

Question 3

What are the differences in structure of MHC I and II molecules?

Answer 3

MHC I: alpha chain anchored to membrane with invariant beta chain covalently bound, alpha 1 and 2 are polymorphic (peptide binding cleft), alpha 3 is invariant
MHC II: polymorphic alpha and beta chains both anchored to membrane; alpha and beta 2 are invariant

Question 4

What are the differences in structure of MHC I and II molecules?

Answer 4

MHC I: alpha chain anchored to membrane with invariant beta chain covalently bound, alpha 1 and 2 are polymorphic (peptide binding cleft), alpha 3 is invariant
MHC II: polymorphic alpha and beta chains both anchored to membrane; alpha and beta 2 are invariant

Question 5

What are the characteristics of peptides displayed by Class II MHC molecules?

Answer 5

-longer peptides (10-30 aa’s) from exogenous extracellular proteins

Question 6

What cells contain class II MHCs?

Answer 6

professional APCs: macrophages, dendritic cells, B cells, human endothelial cells

Question 7

What alleles are displayed for MHC II and how many molecules can be expressed per cell?

Answer 7

HLA DR, DQ, and DP; codominant expression= 10-30 different class II MHCs

Question 8

How does the T cell receptor have dual recognition?

Answer 8

1st recognizes the peptide fragment, 2nd recognizes the polymorphic regions of the MHC

Question 9

T/F:MHC molecules have low affinity and high specificity

Answer 9

False!: Low affinity and broad specificity; many different peptides can bind to the same MHC molecule