Major Histocompatability Lecture 6

Question 1

What are the two main types of MCH gene products?

Answer 1

Class 1 and class 2 molecules

Question 2

What are the three types of genetic loci that make up the HLA?

Answer 2

Class 1, class 2, class 3

Question 3

What are the loci within class 1? Where are these molecules present? What cells do they present antigen to?

Answer 3

HLA-A
HLA-B
HLA-C

Virtually all nucleated cells

Present antigen to CD8+ Tlyphocytes

Question 4

What are the loci within class 2? where are these molecules present? What cells do they present antigen to?

Answer 4

HLA-D 
Subset loci (DR, DQ, DP)

• these molecules are found on dendritic cells, b-lymph, and macrophages
• Present antigen to CD4+T lymphocytes

Question 5

What type of cell do class 3 loci present to?

Answer 5

Dont present antigen to T-lymphocytes

Question 6

Where is the HLA complex found?

Answer 6

Short arm of Chromosome 6

Question 7

What does the cell surface molecule of Class 1 look like?

Answer 7

• 1 alpha chain (class 1 polypeptide) (44,000 daltons)
• 1 light chain beta2 microglobulin (specified by a gene on anothr chromasome) (12,000 daltons)

-they are associated non-covalently

Question 8

What holds up the a2 and a1 chains on the MHC class 1 molecule?

Answer 8

B2 and a3 make up a beta pleated sheet platform

Question 9

What do the two helices on the MHC class1 molecule form?

Answer 9

Cleft that binds antigenic peptide fragments

Question 10

Which class 2 loci code for?

Answer 10

2 polypeptide chains
a chain (34,00 daltons)
b chain (29,00 daltons)

-alpha 1 and beta 1 make cleft

Question 11

What type of peptides does MHC class 1 bind vs MHC class 2?

Answer 11

MHC class 1: short peptides of 8-10 aa in length 
MHC class 2: longer peptides of 13-17 aa in length

Question 12

Are anchor residues that bind a particular MHC class 1 molecule need to be identical? How else do peptides bind to class1 MHC molecules?

Answer 12

No but they are always related such as all hydrophobic.

-Also bind through their amino and carboxy termini

Question 13

Are anchor residues that bind a particular MHC class 2 molecule need to be identical?

Answer 13

No but they are always related such as hydrophobic, negatively charged, basic aa, hydrophobic

Question 14

Where do the proteins that are encoded by MHC start out then go to and as what?

Answer 14

associate with the ER and then shuttle to the cell surface where they are membrane glycoproteins

Question 15

How are MHC antigens codominatly expressed?

Answer 15

each individual express 3 maternal and 3 paternal for class 1 and 3 maternal and 3 paternal for class 2

Question 16

Does each individual have 2 half sets of genes both expressed equally?

Answer 16

yes

Question 17

What is MHC restriction?

Answer 17

The dependence of the T cells reactivity on
1. Ag
2. MHC products
rather than just the Ag alone

Question 18

What do cytotoxic T lymphocytes recognize?

Answer 18

complex of viral peptides with MHC class 1 and kills infected cells

Question 19

What do T helper lymphocytes recognize?

Answer 19

foreign Ag plus the products of class 2 loci