Lecture 19 + 20 - blood groups Flashcards
what are surface antigens composed of
glycoproteins
glycolipids
what chromosome are genes encoding ABO antigens on
chromosome 9
what do ABO genesdo
- produce glycotransferases
- add sugars to H substance (by making the enzymes that are responsible for adding it)
what does O gene add to H substance
no effect
what does group A gene add to H substance
N-acetyl galactosamine (GlcNAc)
what does group B add to H substance
D-galactose (Gal)
what is the cause of productions of antibodies
produced in response to the environemnt
as many things in nature have similar complexes to RBC sugars = elicit production of antibodies
what antibodies does AB type have
none
what antibodies does O type have
anti A and anti B
subtypes of type A and their prevelance
A1 = 80%
A2 = 20%
when might subtypes create an issue for transfusion
repeated transfusions can cause a reaction
what is the Bombay phenotype
- cant form 2-L-fucosyltransferase necassary for H substance formation
- so NO h substance
- and so present as O type
- but they have antibodies to A, B (like O) and H substance
- but when transfused with O = agglutinates
- can only have blood from eah other
all the antigens of Rh blood group system
C
c
D (biggest clinical influence)
E
e
what are the genes for the Rh blood system
RhD = codes proteins with D antigen
and RhCE = codes for RhCE protein with C, c, E and e antigens
RHD gene
on chromosome 1
is dominant
if you inherit even one Rh+ then you are positive
its either present or not
RHCE gene
can have 4 variations
what is R0 blood type
someone with R0 is always +ve, and has Dce
so always have the D gene