Immunohemotology Flashcards
O: cell antigens, ABs, safe donors, safe recipients, possible genotypes
o Cell antigens: none (unless given to Bombay patients) o Antibodies: anti-A, anti-B o Safe donors: O o Safe recipients: all (not Bombay) o Possible genotypes: OO (recessive)
A: cell antigens, ABs, safe donors, safe recipients, possible genotypes
o Cell antigens: A o Antibodies: anti-B o Safe donors: O, A o Safe recipients: A, AB o Possible genotypes: AA, AO
B: cell antigens, ABs, safe donors, safe recipients, possible genotypes
o Cell antigens: B o Antibodies: anti-A o Safe donors: O, B o Safe recipients: B, AB o Possible genotypes: BB, BO
AB: cell antigens, ABs, safe donors, safe recipients, possible genotypes
o Cell antigens: A and B o Antibodies: none o Safe donors: all o Safe recipients: AB o Possible genotypes: AB
most common blood types –> least common
O>A>B>AB
Name the antibody class of most ABO isohemagglutinins
IgM (Can’t cross the placenta!)
Explain the ABO antigen situation in a person of Bombay blood type, and the consequences of a transfusion of non-Bombay blood into such a patient
you lack even the basic fucose sugar on your ABO antigen. So even if you have an A or B sugar-adding enzyme, they can’t be added to the ABO antigen (no fucose). Bombay folks type as O (antibodies to both A and B), but actually have antibodies to O (thus will result in ABO-mismatch reaction). Probably best approach is for the individual to bank their own blood in case of emergency.
Define the crossmatch, and explain why it is important.
From least to most sensitive:
(1) donor red cells + patient’s plasma. You’re looking for agglutinating antibody reactions (the worst of which would be an IgM anti-ABO reacton). If the cells agglutinate, then there’s a really severe reaction going on. DON’T use that blood
(2) look for ABs that are there but not expressing themselves under those conditions. Repeat the donor red cells + recipient plasma test under low-ionic solutions (this minimizes red cell-red cell repulsion and allows the agglutination test more sensitivity).
(3) Coombs indirect test. If agglutination occurs, it’s a sign, again, of red cell antibodies. This test is extremely sensitive and it’s the last way you crossmatch the red cells before giving them to the recipient.
Explain how red cells are destroyed following a mismatched transfusion, and why this may be devastating to the recipient.
• Cells are destroyed in a mismatched transfusion the same way any other antigen would be in the presence of antibodies to it. Since the antibodies are IgM, this is mostly complement-mediated lysis, opsonization, anaphylaxis, and inflammation. There seems to be a competition among which complement result can kill your patient fastest, but lysis, with precipitation of hemoglobin in the blood, resulting in emergent kidney failure and death, is currently on top.
direct antiglobulin test: technique and question designed to answer
Do these red cells already have antibody on them? Tested by adding anti-antibody directly to washed cells.
o i.e. autoimmune hemolytic disorders
indirect antiglobulin test: technique and question designed to answer
Are there antibodies in this plasma that could react with these red cells I have?
o This involves using antibody to human antibodies: apply red cells + recipient serum, wash off any unbound recipient antibody, and then use antibody against human-antibody to detect any bound recipient antibodies on the donor red cells. If agglutination occurs, it’s a sign, again, of red cell antibodies.
o i.e. crossmatching blood before transfusion
Heterophile antibody:
antibody that reacts with more than one antigen. This fact is used to come up with easy ways to test if the antibodies a person is making are against particular organisms
identify a common disease in which one type of heterophile AB is increased enough to be useful diagnostically
antibodies against the Epstein-Barr virus (mononucleosis) in humans are the same antibodies, or as close as makes no difference, as antibodies against sheep red blood cells. If you have someone you suspect has mono, you can test their antibodies against sheep’s blood cells and come up with your answer
HDN: the consequences of severe hemolysis in the newborn
• If a child is undergoing massive hemolysis, then heme’s breakdown product, bilirubin, can spill across the blood-brain barrier, causing cerebral palsy in the fetus. To avoid this outcome in neonates you can put the newborn under bilirubin lights or do exchange transfusions
HDN: the way in which the mother becomes sensitized
Largest transfusion of blood cells from fetus to mother occurs during placental separation, at birth. Note that if you infuse the mother at the point of delivery with anti-Rh antibodies, Rh proteins never make it to the lymph nodes to be made into antibodies. This helps prevent the sequential worsening of the condition with subsequent pregnancies.
- Newer treatment: Put in one shot at 28 weeks, the other at birth. Can also give a shot after any kind of trauma that results in fetal blood leaking into the mother’s circulation.
- Notice that this is a prophylaxis only– does not reverse the fact that there’s maternal antibodies to the infant’s blood.
HDN: the class of antibody to Rh(D) the mother makes
negative (so can make ABs against the baby’s postive!)
HDN: the consequences of sensitization to subsequent fetuses
The anti-Rh dose is low enough that the fetus is more or less unaffected.
HDN: the role of Rh-immune globulin
These antibodies combine with the fetal red cells, opsonizing them, and they are destroyed before they get a chance to immunize her. Note: she is not made tolerant -> just not immunized. She must receive Rh immune globulin each time there is a chance of being immunized by Rh(D)-> cells: this includes all subsequent normal deliveries, abortions, fetal manipulations, amniocenteses, etc
Explain the situation in which ABO hemolytic disease of the newborn can occur
some women, in rare cases, do make IgG hemoagglutinins to ABO antigens instead of/in addition to IgM. This results in refractory hemolytic disease of the newborn. So if an O, A, or B mother has an AB kid, the kid’s blood is not long for this world
