Transfusion Immunology Flashcards
what are the 3 basic concepts involved in blood groups and transfusion reactions?
1- self and foreigness
2- T dependency and independency
3- genetic polymorphism and inheritance
blood cell antigens are what kind of antigens?
alloantigens
what determines the chemical composition of blood cell antigens?
polysaccharide determined by glycosyl transferases
what are the mechanisms of inheritance of blood cell antigens?
…
what are the mechanisms of expression of blood cell antigens?
dominant or codominant
what gene codes for the backbone in the sugar moiety?
H gene
what does the H gene encode?
a fucosyltransferase which encodes the O antigen base structure
the H gene is absent in which form of leukocyte deficiency?
Bombay blood group phenotype
sugar for A allele
N-acetylgalactosamine glycosyl transferase
sugar for B allele
galactosyl transferase
the carbohydrate structure is recognized by which cells?
B cells (found only in individuals not expressing the phenotype)
Natural antibodies or isohemagglutinin immune responses against the shared bacterial antigens are dependent on which cells?
T cells
Is the H allele recessive or dominant?
recessive
- it is considered recessive because individuals develop antibodies against the missing blood group antigen around the 3-6th month of life
Anti-A and Anti-B antibodies represent what class?
IgM
what are the other blood groups?
secretor Lewis MNSs Kell Duffy
secretor
most of us encode a gene which allows the A,B and H antigens to be secreted
Lewis
LeA and LeB are not ABO linked by are structurally related; natural antibodies in Le- individuals
MNSs
- MN group located on glycophorin A
- Ss group on glycophorin B
Kell
- K and k allelic forms; K is the stronger antigen
- protein antigen may provoke strong transfusion reaction and HDN
Duffy
Duffy antigen receptor for chemokines (DARC)
- FyA or FyB - an important receptor on RBCs for the malarial parasite Plasmodium vivax; also binds various chemokines
- Fy- or Duffy null - 60% African or of African descent
the Rh system has how many different antigens?
44
which of the 6 alleles of the Rho system is clinically the most important because of its high immunogeneicity?
D
when does Rh appear in a human?
early fetal development
induced antibodies in Rh- person can be found following which events?
- mis-matched transfusion
- pregnancy
- abortion
transfusion reactions occur due to reactivity btw _____ antibodies and _____ red blood cells
recipient
donor
what hemolytic symptoms occur after an incompatibility rxn?
diffuse muscular pain headache vomiting rise in temperature shock renal failure
what is the primary means by which HDN occurs?
Rh- mother has a Rh+ baby
what is the second most common HDN blood group?
Kell
under what condition would HDN happen to the first baby?
1- if mother had previously received mismatched transfusion
2- mother had a previous miscarriage or abortion of an Rh+ baby
in HDN mother becomes _____ with baby’s cells when they enter ______during first pregnancy; this number is ususally too low to induce problems for that baby
sensitized
circulation
What are the steps for HDN that begin with a mother is pregnant with her first Rh+ fetus?
1- sensitization of mother
2- during delivery, Rh+ from cord blood mix with mom’s blood
3- mother becomes immunized producing anti Rh+ IgG
4- IgG can cross placenta and damage subsequent Rh+ fetus
___ incompatibility MAY diminish the possibilities of HDN
AB;
Normally occurring anti-A and anti-B blood groups in the mother may clear antigenic Rh+ fetal RBCs and prevent sensitization
approximately what percent of cases are due to ABO incompatibility?
50-60%;
Cases are usu minor with transient anemia and jaundice with slightly elevated bilirubin
Direct Coombs testing purpose
detects presence of antibodies on RBCs
INdirect Coombs testing
detects presence of antibodies against RBC antigens
cross matching
matches rbc of donor against serum of recipient to avoid reaction against other antigens (indirect coomb’s)
practice coombs
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