Final Exam (Lecture 20) - Type II Cytotoxic Hypersensitivity Flashcards
List the components of the Type II reaction and describe their role in a Type II hypersensitivity reaction. Highlight the antibody that most commonly mediates this reaction.
Antibody to cellular target:
- IgG but can be IgM
Cellular target:
- Antigen on cell surface
Describe how cellular targets are destroyed. Compare and contrast to other killing mechanisms discussed.
1) Complement fixation/cell lysis:
- IgG coats the cell
- Complement fixation
- MAC lyses cell
2) Opsonization and phagocytosis:
- IgG opsonizes cell
- Phagocytosed by macrophage/neutrophil
3) ADCC:
- IgG coats cell
- NK cells, macrophages, and neutrophils bind via
FcR and kill cell
4) Macrophages release granule contents and oxidative
metabolites; NK cells = apoptosis by perforin and
granzyme
Explain the difference between natural antibodies and immunogenic RBC antigens (no natural antibody to these).
1) Natural antibodies:
- Are IgM (B cells do not isotype switch)
2) Immunogenic RBC antigens:
- Stimulate an immune response upon exposure
- Antibodies form afer exposure
- The individual becomes sensitized
Describe the human, cat, dog, and horse blood types in this lecture (important antigens, natural antibodies, and immunogenic antigens).
1) Human:
- Antigen: Rh factor, A, B
- Natural antibodies: A, B, O (has natural to both)
- Immunogenic antigens: Rh
2) Cats:
- Antigen: A, B
- Natural antibodies: A, B
- Immunogenic antigens: A if given to type B; and
vice versa
3) Dogs:
- Antigen: 8 blood group antigens
- Natural antibodies: No
- Immunogenic antigens: 1.1, 1.2
4) Horses:
- Antigen: A, C, Q, U, K, D, P
- Natural antibodies: No
- Immunogenic antigens: A, Q
Define blood typing and identify the blood type of an animal when given information from a card test.
Blood typing:
- Determining patient blood type based on which
antigens are present on the RBC
Identifying blood type:
- Ex: If anti-A antibodies are present on the blood
typing card and there is agglutination when the
patient blood is added, the patient has type A blood
Describe what is mixed together for a major crossmatch and the results you look for.
Donor RBCs and recipient serum
Look for cell lysis and agglutination
Explain why blood typing and cross-matching are especially important before a blood transfusion in some exotic breeds of cats.
Exotic breeds tend to be type B and they have anti-A antibodies that are strongly hemolytic.
If a cat with type B blood is given as little as 1mL of type A blood, it can lead to shock.
Explain why it has been said that you can do one transfusion without a cross-match in the dog.
Dogs do not have natural antibodies.
However, DEA 1.1 and 1.2 are highly immunogenic and elicit a response and become sensitized.
- So the next time, it would elicit a transfusion
reaction
Explain the factors that result in hemolytic disease of the newborn.
Not seen with first pregnancies; only subsequent ones due to mother developing antibodies to newborn’s RBC antigen.
- It is a concern because IgG can cross the placenta
- Antibodies will be in colostrum which will cause
RBC lysis in the newborn
Describe a major difference between hemolytic disease in humans compared to foals and how each is prevented.
1) Humans:
- Problems in utero (across placenta)
2) Horses:
- Problems with colostrum
You are presented with a very anemic exotic breed of cat. This is a very special cat, and the owner is extremely worried. She has plans to breed this cat. You determine that a transfusion is required. You remember from immunology that you can’t just grab any cay to us as a donor for the transfusion. You explain to the owner that you will be blood-tying the cat and doing a major cross-match before giving the cat a transfusion. Please explain the following:
- Why do you do the major cross-match (what do you want to know)?
- What do you mix together to do a major cross-match?
- List two reactions of the cross-match that would indicate incompatibility.
1) You do major cross-matching to ensure that there will
be no transfusion reaction after the transfusion is
performed (make sure the recipient isn’t going to
destroy the RBCs it receives).
2) Donor RBCs and recipient plasma.
3) Cell lysis and agglutination
You blood type the cat (from previous question) using the card test with antibody against the red cell antigen lyophilized on the card. There is agglutination under the B, and no agglutination under the other.
- What is the cat’s blood type?
- Draw a picture of the cells and molecules leading to the result you see.
1) The cat’s blood type is B
2) See notes (lecture 20 study questions)
If this cat is bred and the kittens have a different blood type than the queen, will the kittens have a problem in utero? Why or why not? (Think about the isotype of the antibody that you are concerned about).
No because IgM does not cross the placenta.
One of the blood types in horses is A. Horses with type A blood have the A antigen (A+) on their RBCs. This antigen is very immunogenic in horses who are negative for the A antigen (A-). If a mare who is A- is bred to a stallion who is A+, the fetus may be A+. There isn’t a natural antibody to the A antigen but exposure to the A antigen will induce an immune response resulting in high-titered IgG. So, during parturition, the mare is exposed to the foal’s RBCs with the A antigen. On a subsequent pregnancy resulting from this mating, there is a risk of neonatal isoerythrolysis (hemolytic disease of the newborn).
- Is the foal at risk in utero?
- After colostrum?
- How are the RBCs destroyed?
- If you wanted to give RBCs to the foal and you only had the choice of giving RBCs from the mare or the stallion, which would you choose and why?
1) No
2) Yes
3) IgG from mare binds to foal’s RBCs and cause lysis
4) Washed RBCs from the mare because she doesn’t
have the antigen
