Hypersensitvity Type II - Hunter

Question 1

What does Type II Hypersensitivity (TIIH) involve?

Answer 1

It involves IgG antibodies that bind to cells or tissues and engenders an immune response.

Question 2

Name some mechanisms of TIIH.

Answer 2

1. antibody binds causes opsonization with or without complement and triggers phagocytosis.
2. antibody binds and fixes complement and induces inflammation. This occurs if the phagocyte cannot phagocytose and instead releases its mediators. This occurs when antibody binds to fixed tissues and is called frustrated phagocytosis.
3. antibody binds to receptor on self cell and inhibits binding of its normal ligand or the antibody stimulates the receptor.

Question 3

What is mismatched transfusion?

Answer 3

When a person gets a blood transfusion that involves blood of a different blood type their body will mount an immune response by pre-existing natural antibodies to A and B blood group antigens. This is a Type II hypersensitivity reaction.

Question 4

What are the 2 mechanisms of antibody-mediated RBC destruction in?

Answer 4

1. anti-RBC antibodies engage Fc receptors on macrophages and promote phagocytosis and killing.
2. Anti-RBC antibodies can activate complement and promote RBC hemolysis.

Question 5

What is a natural antibody?

Answer 5

B1 type of Bcells can make natural antibodies without T cell stimulation but only to a very few specific things - one of these is the carb groups on the membranes of RBC’s that determines blood group.

Question 6

Describe immunohemolytic anemia?

Answer 6

1. RBC surface proteins are conjugated to penicillin happen.
2. In the presence of a danger signal this hapten complex is presented to CD4 T cells.
3. B cells that also recognize the hapten complex receive T cell help and begin to produce anti-penicillin antibodies.
4. Antibodies bind to penicillin modified RBC’s and cause their destruction via phagocytosis or complement mediated hemolysis.

Question 7

Describe hemolytic disease of the newborn.

Answer 7

1. An Rh- mom is pregnant with an Rh+ baby. During birth the baby’s blood is transferred to mom and she mounts an immune response against Rh, making Rh antibodies and memory B cells.
2. If mom becomes pregnant with an Rh+ baby again, her IgG antibodies to the Rh will cross the placenta and will cause hemolysis of the fetal RBC’s. This can lead to severe anemia in the fetus leading to heart failure and massive edema. If the baby survives it may have brain damage due to the heme metabolite bilirubin.

Question 8

How can you test to see if the fetus of an Rh- mom is Rh positive?

Answer 8

1. direct coombs test - take fetal blood and wash then add rabbit anti-human antibody, wash again. If the baby’s RBC has the Rh antibody attached then the rabbit anti-antibody will agglutinate.
2. indirect coombs test - take a sample of mom’s serum and add Rh+ RBC’s, wash and then add rabbit anti-human antibody and wash again. If mom had Rh antibodies they will attach to the Rh+ RBC’s and then the anti-human antibody will attach and cause agglutination.