27- Transplantation and Transfusion Immunology

Question 1

What is the importance of MHC as an antigen in transplant rejection?

Answer 1

They are highly polymorphic and are unlikely to be similar between individuals. Polymorphic variants can thus be recognized as foreign antigens when shared between individuals

Question 2

MHC II is the most important alloantigen. Why?

Answer 2

MCH II is expressed on APCs and present exogenous antigens from endosomes/lysosomes and consists of polymorphic alpha and beta chains

Question 3

Name the four types of tissue grafts and their definitions

Answer 3

• Autograft (autologous): from one individual to self
• Isograft (syngenetic): Between two genetically identical individuals
• Allograft (allogenetic): Between genetically different individuals of the same species
• Xenograft (xenogeneic): between individuals of different species

Question 4

What is the mechanism for hyperacute reactions?

Answer 4

• occur within minutes
• directed against graft vasculature
• due to the presence of preformed antibodies
• typically directed against blood type antigens that are also expressed on the surfaces of endothelial cells
  This is very rare because you usually ensure both individuals have the same blood type

Question 5

What is the mechanism for acute reactions?

Answer 5

• occur within days to weeks
• mediated by T-cells and antibodies specific for alloantigens
• current immunosuppressive therapy is directed at preventing acute reactions (by suppressing lymphoid activation or antigen recognition)

Question 6

What is the mechanism for chronic reactions?

Answer 6

• occur over months to years
• adaptive immune response
• mediated by T cells and antibodies specific for alloantigens
• current immunosuppressive therapy is NOT effective at preventing

Question 7

RBCs don’t have MHC, rather each blood type is characterized by the presence of specific _________.

Answer 7

Glycoproteins

Question 8

Animals may make antibodies to foreign blood group antigens. If pre-existing antibodies are present, they can recognize and bind RBC antigens leading to __________, _________, and ____________.

Answer 8

Agglutination, hemolysis, opsonization

Question 9

What are the major RBC antigens in cats?

Answer 9

A, B, AB blood types: A is dominant

Question 10

What are the major RBC antigens in canines?

Answer 10

DEA 1.1, 1.2, 3, 4, 5, 6, 7, 8
DEA 1.1 is most antigenic

Question 11

What are the major RBC antigens in horses?

Answer 11

A, C, D, K, P, Q, U
Aa and Qa are most antigenic

Question 12

What is the mechanism for transfusion rejections in cats?

Answer 12

Cats have pre-formed antibodies. 2/3 of Type A and all of type B have high antibodies of the opposing type. If given blood opposite of their type, it would cause a hyperacute reaction

Question 13

What is the mechanism for transfusion rejections in dogs?

Answer 13

Dogs do not have iso-antibodies to incompatible blood groups until there is an initial exposure. About 2/3 of dogs are DEA 1.1+ which is the most antigenic and that means they can receive blood from any donor. If any dog that is DEA 1= dog is transfused with blood from a + blood donor, the dog will become sensitized. This means if this dog was to receive another transfusion with the same blood type, it will lead to a hyperacute reaction

Question 14

What is the mechanism for transfusion rejections in horses?

Answer 14

Same as in dogs. However, is a mare is previously sensitized to the same blood type that their foal has, it can lead to HDN (Neonatal Isoerythrolysis) of the newborn.

Question 15

When giving packed RBCs, you need roughly _____ml/kg to increase the PCV by 10%.

Answer 15

10

Question 16

When using whole blood, you need roughly ____ml/kg to increase the PCV by 10%.

Answer 16

20