WEEK 3: ABO Blood Groups Flashcards
what is a blood group?
An inherited character of the red cell surface detected by a specific alloantibody
what is the biological role of a blood group? (4)
–Recognition of self and non-self
–Maintenance of cellular integrity
–Involvement in cell maturation
–Susceptibility or resistance to disease
which two classes of immunoglobulin are of interest in blood groups for transfusion?
IgM and IgG
what is the structure of IgM?
pentameric - means 5 sub units. It is a big molecule
how many antigen binding sites does IgM have?
10
why do rbcs repel each other?
the membrane has a negative charge
do IgM anti bodies cross the placenta?
no.
what temp does IgM work best?
below 37 celcius
what is the structure of IgG?
monomeric (a protein that has a single polypeptide chain)
how many antigen binding sites does IgG have?
2
Which antibody causes agglutination? IgM or IgG?
IgM
can IgG cross placenta?
yes.
why doesn’t IgG not usually bind complement?
there’s not enough to activate cascade
what percentage of people in the UK have the blood group O?
47%
what percentage of people in the UK have the blood group A?
42%
what percentage of people in the UK have the blood group B?
8%
what percentage of people in the UK have the blood group AB?
3%
what 3 genes governs the presence of A and B blood groups?
H gene, A gene and B gene
what chromosomes are H, A and B genes located on?
H is on chromosome 19. A and B are both located on chromosome 9 and are co-dominant alleles.
what enzyme does the H gene code for?
H enzyme
what enzyme does the B gene code for?
B enzyme
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what genotypes produce blood group A? (2)
AA and AO
what genotypes produce blood group B? (2)
BB and BO
what genotype produces blood group AB?
AB
what genotype produces blood group O?
OO
what percentage is there of each subgroup of A antigen?
*A1 –80%
*A2 –20%
when do antibodies develop?
over the first 4 months after birth
are ABO antigens sugars or proteins?
sugars
what is Landsteiner’s Law?
ABO antibodies are found in the plasma against the ABO antigens an individual lacks
give the antigen on rbc and antibody in plasma if patient has blood group O.
antigen on rbc - none
antibody in plasma - anti-A and anti-B
give the antigen on rbc and antibody in plasma if patient has blood group A
antigen on rbc - A
antibody in plasma - anti-B
give the antigen on rbc and antibody in plasma if patient has blood group B
antigen on rbc - B
antibody in plasma - anti-A
give the antigen on rbc and antibody in plasma if patient has blood group AB
antigen on rbc - A and B
antibody in plasma - none
when do antigens develop?
development over first 1-2 years of life
what gene allows the RhD antigen to be incorporated into the cell?
RhAG gene on chromosome 6
what are the characteristics of weak D?
- possesses all normal D antigens but has less
- cannot produce anti-D
what are the characteristics of partial D?
- lacks part of a normal D antigen
- can produce anti-D
- regarded as RhD neg as a donor
what do RhD negative individuals lack?
they lack the D antigen (no RhD gene)
