Hypersensitivity type 2 Flashcards
What is a hypersensitivity type 2 reaction defined as
Destruction of normal tissue/cells by antibody (specifically IgG or IgM) with activation of complement or antibody dependent cell cytotoxicity (using NK cells)
Common examples of hypersensitivity type 2 reactions
Blood transfusion reactions
Hemolytic anemia of newborns
Penicillin induced anemia
Some autoimmune disease
Why are red blood cells commonly affected in type 2 hypersensitivity reactions
Because they do NOT display MHC
Transfusions are performed with
Blood loss
Trauma
Surgery
Low RBC count
How high is the risk of a reaction to a blood transfusion
Species dependent because some species are able to receive “one free” transfusion without a risk of reaction (body has no antibodies/it was never sensitized to another blood type)
What is ACD (acid citrate Dextrose) solution used for
Used in blood collection as an anticoagulant and energy source for red blood cells
Often found in human blood collection packs
What is the formula for ACD solution
Trisodium citrate 22.0g
Citric acid (monohydrate) 8.0g
Dextrose (monohydrate) 24.6g
Distilled water to make it up to 1L
For each 100ml of blood collected, you need ___ml of ACD solution (pH 5.0)
15 ml
Blood group antigens: name often starts with a species code and EA (erythrocyte antigen) followed by a letter or number denoting the order of discovery, what is DEA1.1
DEA: dog erythrocyte antigen
1.1: first allele of antigen 1
A recipient of a blood transfusion may contain pre existing antibody as a result of;
Previous blood exposure or exposure through the diet
The risk of dietary exposure to a blood group antibody is species dependent, who is it often seen in and why
Cattle and some cats
Due to ingesting colostrum with antibodies
What is the mechanism behind a blood transfusion reaction
Pre existing antibody binds to the erythrocyte antigens and activates a complement reaction Causing
Hemolysis
Anaphylatoxin release and mast cell degranulation
Free hemoglobin (can cause secondary damage to the kidneys)
How do you prevent transfusion reactions
Cross matching
The most important cross matching technique is a major cross match, describe this
Using the donors RBCs and the recipients serum
Look for lysis (complement) and agglutination
What is a minor cross match (less important)
Donor serum and recipient RBCs
What are the signs of a mild to moderate transfusion reaction
sweating, salivation, diarrhea vomiting, increased RR/HR
What are the signs of a severe transfusion reaction
Shock Weakness Hyperpnea Hypotension Collapse Death (arrhythmia or apnea)
What are the signs of the recovery phase of transfusion reactions
Hemoglobin from ruptured RBCs eventually converted to bilirubin
Icterus (yellowing) of mucosae and sclera
Describe blood transfusions in cattle
MANY blood types
Blood typing used to check parentage
Transfusions are often incompatible
Some cattle have pre-formed antibodies against foreign RBCs often due to dietary antigens
First transfusions last days to a week
Repeated transfusions needed for the shorter life of RBCs
Dogs have no preformed antibodies against foreign RBCs, they do have many RBC antigens though, what is the major antigen in dogs that causes most problems with transfusions
Only one group, DEA 1 (strong antigen) (there is a card to test this antigen)
DEA 1.1 is a subgroup and the major cause of concern with DEA 1 dogs
40% of dogs are DEA 1.1 positive. They can receive blood from DEA positive AND negative dogs, making them universal blood recipients
if DEA 1.1 (an ideally 1.2) positive dogs are universal recipients, what does that mean for DEA 1.1/1.2 negative dogs
Universal blood donors (don’t need to worry about most dangerous group of antigens)
Greyhounds are universal donors because most are DEA negative
What happens when you transfuse a DEA 1.1 negative dog with a DEA 1.1 positive dog
First transfusion is “free” -it will be okay because there is no preformed antibodies but the body will start to make new antibodies for the next exposure
Transfusion reactions will be seen on subsequent transfusions
This is a common problem in puppies (neonatal isoerythrolysis)
Recommended that you always ____ on subsequent transfusions in breeding bitches
Cross match
Does antigen testing for strong antigens prevent:
Problems on first transfusions: yes
Problems on subsequent transfusions: yes (small risk of incompatibilities from minor antigens)