Immunohematology Flashcards
T or F: RBC’s carry MHC molecules
False
T or F: Platelets carry MHC molecules
True. People repeatedly needing platelets, which do bear HLA (Class I), they may develop an alloimmunization problem, in which case HLA typing as well becomes necessary.
What are blood group antigens?
Blood group antigens are glycolipids found on the surface of all body cells, including of course red cells
What are A, B or O. Blood group substances ?
glycoproteins with similar sugars, found in the body fluids of people who have the Secretor (Se) phenotype
What is the most common blood groups?
O type and Rh+
Least common blood groups?
AB type and Rh-
Group A plasma antigen and possible genotype?
- Anti-B
- AA or AO
Group B plasma antigen and possible genotype?
- Anti-A
- BB or BO
Group AB plasma antigen and possible genotype?
- None
- AB
- universal recipient
Group O plasma antigen and possible genotype?
- Anti-A & B
- OO
- Universal Donor
What is the the Bombay phenotype (Oh)?
some people who lack the transferase gene that puts the final sugar on the “core”, and thus do not express even the H antigen. Very rare. All blood, even type O, is foreign to such people.
What are ISOHEMAGGLUTININS?
Very common in environment and you will become immunized to them. These antibodies are sometimes called “naturally-occurring,” although like all antibodies we believe that their production is in response to antigenic stimulation. Are of the IgM class
What allele do we care about for Rh factor?
D allele
Is Rh an isoheamagglutinin?
No. you don’t make antibody to it unless you’re Rh(D)- and become immunized with Rh(D)+ red cells.
Define crossmatching.
antibodies in a recipient’s plasma which can react with antigens on donor’s red blood cells. The crossmatch therefore is a lab test in which plasma from the prospective recipient is mixed with red cells from the prospective donor and observed for agglutination.
What is the direct anti globulin test?
asks, is there antibody already on these cells I am interested in? You rinse off the cells and add antiglobulin to find out. The direct test detects cells that were coated with antibody in vivo.
What is the INdirect anti globulin test?
asks, is there unexpected antibody to red cell antigens in the plasma of this potential recipient? You take red cells, add the plasma, rinse the cells (we assume they haven’t agglutinated,) and then add antiglobulin. If the cells now agglutinate, there must have been antibody to them in the plasma, because antiglobulin alone won’t react with red cells.
Define Heterophile antibody.
These are antibodies to one antigen which bind, fortuitously, to another; a fancy name for cross-reactive antibodies. Appears in pts with infectious mononucleosis and binds to sheep red blood cells. Known as the Monospot test.
List Consequences of severe hemolysis in the newborn with Hemolytic Disease of Newborn (HDN)
high levels of bilirubin (a breakdown product of hemoglobin) can cross the blood-brain barrier and damage the basal ganglia, resulting in cerebral palsy or, if there is very severe damage, fetal death.
How is a mother sensitized in HDN?
Exposure to Rh+ baby blood while being Rh- during delivery of 1st child.
What class of Ab to Rh(D) that the mother makes?
IgG (crosses the placenta, kills RBC)
What are the consequences of sensitization to subsequent fetuses?
HDN disease
What is the role of Rh-immune globulin?
IgG antibody to Rh(D). These antibodies combine with the fetal red cells, opsonizing them, and they are destroyed before they get a chance to immunize her.
Explain how ABO hemolytic disease of the newborn can occur.
Occasional people do make IgG isohemagglutinins. This is especially true of group O people. So A or B fetuses of these women are at some risk of ABO hemolytic disease
