Immunogenetics and Transplant

Question 1

What is the MHC or HLA?

Answer 1

MHC= Major Histocompatibility Complex
HLA= Human Leukocyte Antigen

It is a region of genes that encode for proteins that are involved in antigen presenting.

Question 2

In which cells do we find Class II MHC (HLA)?

Answer 2

Dentritic Cells
Macrophages
B-cells

Question 3

In which cells do we find Class I MHC (HLA)?

Answer 3

All

Question 4

Why is HLA-DR important?

Answer 4

It is the most expressed class II gene on surfaces of cells and important for transplants

Question 5

What are the most important/expressed HLA s in class I?

Answer 5

A and B

Question 6

Why are transplants so difficult with respect to HLAs?

Answer 6

There are so many polymorphisms in HLA genes because of the gene duplication that happened.

Question 7

What is a haplotype?

Answer 7

The set of alleles at a group of linked loci (no recombination).

I.e. the specific genes you inherit from 1 parent.

Question 8

What are the different genes in the HLA class II?

Answer 8

DP DQ DR

As a group it is also known as HLA-D

Question 9

What are the different genes in the HLA class I?

Answer 9

A, B, C

Question 10

A father’s HLA phenotype is A1, A3, B5, B7, DR9, DR11. The mother’s phenotype is A2, A4, B6, B8, DR10, DR12. They have had a baby whose phenotype is A1, A4, B6, B7, DR11, DR12. What are the father’s, mother’s and child’s haplotypes?

Answer 10

Father-A1,B7,D11 & A3,B5,DR9
Mother- A4,B6,D12 & A2,B8,D10

Child- A1,B7,D11 & A4,B6,D12

Question 11

A father’s HLA phenotype is A1, A3, B5, B7, DR9, DR11. The mother’s phenotype is A2, A4, B6, B8, DR10, DR12. They have had a baby whose phenotype is A1, A4, B6, B7, DR11, DR12. Could they have a child who is A1, A2, B7, B8, DR10, DR11? or A3, A4, B5, B8, DR9, DR12?

Answer 11

Father-A1,B7,D11 & A3,B5,DR9
Mother- A4,B6,D12 & A2,B8,D10

A1, A2, B7, B8, DR10, DR11? Yes
A3, A4, B5, B8, DR9, DR12? No

Question 12

Who is the best possible donor for a patient needing a transplant?

Answer 12

Siblings

There is a 1/4 chance they have the same HLAs as you.

Question 13

How does MLR work and what is it used for?

Answer 13

• Collect WBC from donor and patient.
• Radiate WBC from donor to kill Tcells. (not transplanting T-cells)
• See if patient T-cells react against donor monocytes.

Question 14

Which class of HLA do Th1 cells recognize?

Answer 14

Class II only

Question 15

Describe the cellular and molecular events which go on during graft rejection, including cytotoxic T cells, Th1 cells, and macrophages

Answer 15

• Host Th1 cells recognize Class II HLA on transplanted macrophages or DC.
• Activated Th1 secretes IFN-y and recruits host Macs.
• Also secretes IL-2 which recruits CTLs.

Question 16

What is alloreactivity? And what role does it play in transplants?

Answer 16

Alloreactivity is the immune reaction that occurs between members of the same species.

Your own Tcells are activated by something that looks “not quite like you.” This can be your MHC + antigen, or someone else’s MHC + antigen.

Question 17

How do autoimmune diseases and HLA alleles relate?

Answer 17

Every autoimmune disease is associated with a specific HLA-allele.

Ex. Diabetes type I and DQ2 and DQ8

Question 18

When do hyperacute rejections occur?

Answer 18

When the recipient has a preexisting antibody IgG or IgM against the donor tissue in some way.