Chapter 8 MHC

Question 1

Where are the MHC genes found in humans and mice and what do the 3 classes of MHC do?

Answer 1

humans= 6
mice= 17
Class I= on all nucleated cells
II= on APCs
III= involved in inflammation and complement

Question 2

Genetics of MHC:

How is it inherited, describe why there is so much variance and what does it mean by codominant alleles?

Answer 2

One haplotype from each parent given to child, genes very close so crossing wont over occurs a lot, codominant means they both coexist together

Question 3

Differentiate between the structure and function of MHC I and MHC II

Answer 3

I= presents antigen that accumulate in the cytosol, Alpha one chain, transmembrane and encoded by A, B, C region in humans and a Beta chain encoded by highly conserved gene on chromosome 15

II= Alpha 1 and 2 chain and Beta 1 and 2 chain, present antigen from extracellular spaces that have been engulfed by a cell, DQDPDR, transmembrane

Question 4

Describe in Detail the endogenous pathway for MHCI.

Answer 4

• endogenous antigen broken down by proteosome
• some of the peptide fragments at carried to the Rough ER and bind to MHCI (carried by transporter), this MHCI-peptide complex is processed in the Golgi and then presented on the cell surface for CD8+ Tc cells via exocytosis.

Question 5

Describe in detail the exogenous pathway and how endogenous antigens are blocked

Answer 5

In the RER, there is an invariant chain that binds to the alpha and beta chain of MHCII to block endogenous antigen. This complex is sent to the golgi when a exogenous antigen is engulfed and broken down (receptor mediated endocytosis). When the two meet, the invariant “clip” is removed by HLADM and the antigen and MHC II molecule bind. These are the presented on the cell surface to CD4+ or Th cells via exocytosis.

Question 6

MHC diversity,

- Cheetah screwed why

Answer 6

• inbred species, polymorphism limited.

Question 7

Skin grafts, MHC

Answer 7

medelian genetics