Test 3:Blood group antigens Flashcards
What are the antigenic determinants for blood groups made of and what are they mostly bound to?
Carbohydrates bound to glycosphingolipids
What does the H gene encode for?
Fucosyl transferase enzyme
When can Bombay type (Oh) have type A or B blood?
Never! Without H chain, no other sugars can be added.
What is added in A-group transferase?
N-acetylglucosamine
What is added in B-group transferase?
D-galactose
What sugar is at the end of the O-group chain?
Fucose
What type of antibody can be naturally produced against group A and/or B?
IgM (coming from B2B cells at young age 3-6)
Which Rh gene does not have a recessive allele?
D
When a person has the RHD gene, what is their phenotype?
Rh positive
What do ‘type and screens’ test for?
ABO and Rh; along with antibodies for any erythrocyte antigens
Which Rh antigen is the most immunogenic?
RhD
What are some signs of immediate hemolytic transfusion reaction? (incompatible blood type transfused)
chest pain, nausea, flushing, dyspnea, fever, chills, hemoglobinuria–>shock, DIC (kills RBCs), renal failure
What are signs/symptoms of delayed hemolytic transfusion reactions? (3-10 days later)
fever, anemia, jaundice–could come from second transfusion (IgM–>IgG)
What do hemolytic transfusion complexes activate?
Hageman factor (XIIa) and complement
What effects does the hageman factor have?
- activates Kinin system–>bradykinin dilates and increases permeability–>hypotension–>renal failure
- activates clotting cascade followed by DIC
What effect does complement have?
-intravascular hemolysis and histamine release from mast cells
When is IgG produced from Rh antigen exposure?
-Second exposure; very rapid
What is erythroblastosis fetalis?
IgG anti-D antibodies are formed and cross the placenta which will cause hemolysis of fetal erythrocytes
What is transplacental fetal hemorrhage and how many women have this?
mixing of fetal blood with maternal blood from placental separation–>sensitization of Rh- mothers; 75%
What is involved in Rh prophylaxis?
High titer anti-Rh immunoglobulin (RhIg) administered in the Rh- mother; suppressor T cells are stimulated which inhibits primary response
