LW - graft rejection MHC

Question 1

What is the definition of MHC restriction?

Answer 1

The antigen has to be bound to the correct MHC in order to cause t-cell activation.

Question 2

What are the comparative structural differences of MHC1 and MHC2?

Answer 2

1 heavy chain, 2 heavy chains.
Associated with B2 micro globulin, extended groove.
Short peptides 8-14, longer peptides 15-24.

Question 3

What is the MHC?

Answer 3

A linked series of genes located on a specific chromosome.
Location and complexity differs between species.
Encodes for MHC1, MHC2 and proteins involved in antigen processing and presentation.

Question 4

Describe the genetic organisation of human MHC.

Answer 4

Class II genes -> codes for antigen presentation to CD4+ T-cells
Class III genes -> complement, cytokines, enzymes
Class I genes -> Antigen presentation of CD8+ T-cells.

Question 5

Why can the MHC be described as polygenic?

Answer 5

Contains several copies of MHCI and MHCII

Question 6

Why can the MHC be described as polymorphic?

Answer 6

Multiple variants of each gene in the population.

Question 7

Which features of the MHC make it difficult for pathogens?

Answer 7

Polygenic.
Polymorphic.
Each individual expresses a number of different MHC antigens and this is the “tissue type”

Question 8

How is the MHC inherited?

Answer 8

• Each individual has 2 sets of MHC - MHC haplotype.
• Maternal and paternal sets.
• MHC gene expression is co-dominant.
• Most inheritance is ‘en block’ -> inherit the whole haplotype.

Question 9

Do MHCI genes or MHCII genes have more variation and why?

Answer 9

MHCII genes because different alpha and beta chains can be joined together.

Question 10

What is the chance that 2 siblings can be haplo-identical?

Answer 10

1/4

This means that they could be a potential recipient match for transplantation.

Question 11

Why do chickens have a strong genetic association to disease?

Answer 11

They only have 19 MHC genes.
Has only a single classical class I and class II molecule expressed at a higher level.
This property confers resistance of susceptibility to particular pathogens.

Question 12

What is an autograft?

Answer 12

Graft from the same individual

Question 13

What is an isograft?

Answer 13

Graft from someone who is genetically identical.

Question 14

What is a xenograft?

Answer 14

Graft from a different species.

Question 15

What is an allograft?

Answer 15

A graft from the same species, but a different genetic composition.

Question 16

Why can graft rejection take place in terms of MHC molecules and T-cells?

Answer 16

Transplanted organs from donors bear MHC molecules that differ from the recipient.
Can be rejected because there is a large number of T-cells that are allogenic to MHC.

Question 17

What is alloreactivity?

Answer 17

Immunological basis for graft rejection. This is the recognition of peptides complexed with non-self MHC.

Question 18

Why are MHC types related to disease susceptibility/resistance in veterinary medicine?

Answer 18

There may be a direct role of MHC types in disease or is inherited with other “disease associated genes”
This is known as linkage disequilibrium.