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ABO subgroups represent
Phenotypes that show weaker variable serologic reactivity with commonly used human polyclonal anti-a, anti-b and anti-a,b
Inheritance of ABO subgroups
Alternate allele at the A or B locus
_ subgroups are more common than B subgroups
A
Lectins
Seed extracts that agglutinate human cells with some degree of specificity
A1 lectin
Dolichos biflorus: agglutinates A1 and A1B
B lectin
Griffonia(banderiaea) simplicifolia: agglutinates B cells
H lectin
Ulex europaeus: agglutinates O cells (H specificity) and other ABO groups based on H antigen sites available
H lectin reacting strength
O>A2>B>A2b>A1>A1B
A subgroups are _% A1 or A1B
80
A subgroups are _% A2 or A2B
20
Quantitative difference between A1 and A2
Decreased # of antigen sites, lower amount of transferase enzyme, and lower amount of branching
Qualitative difference between A1 and A2
difference in precursor oligosaccharide chains, subtle difference in transferase enzyme, and formation of anti-a1 in some subgroups
Inheritance of the A1 gene elicits production of
High concentrations of 3-N-acetylgalactosaminyltransferase which converts all of the H precursor to A1 antigens
A1 antigen sites
810,000-1,170,000
A2 antigen sites
240,000-290,000
Immunodominant sugar for both A1 and A2
N-acetly-D-galactosamine
Difference between A1 and A2
Concentration of 3-N-acetylgalactosaminyltransferase
_% of A2 produce anti-A1
1-8%
_% of A2B produce Anti-A1
22-35%
How is human based Anti-A1 antisera made?
Group B plasma is mixed with A2 cells, anti-a is absorbed into the cells and anti-A1 stays in the serum. Centrifuge, remove the A2 cells, and anti-a1 is left
Anti-A1 lectin resembles
The action of a specific antibody but is not one, it only agglutinates with A1 cells but not A2 cells
Compatible units for an A2 subgroup
1st A2
2nd O
Compatible units for an A2B person
1st: A2 or A2B
2nd: B
3rd: O
Which A type would be more compatible with O platelet products and why?
A2 because they lack the A1 antigen that O makes an antibody to
Besides AB, what group is also considered universal platelet donors?
A2
Subgroups of B are
Very rare
Classifications of B subgroups are made by
Alternate alleles at the B locus
Criteria used to determine weak B phenotypes (5)
Strength of anti-b, anti-a,b, and anti-h
Presence or a sense of ABO isoagglutinins in serum (back typing)
Absorption in elution studies
B soluble substance in saliva
If galactose gene is present
Bombay genotype defect
Defect in FUT1 (H gene) and FUT2 (secretor gene)
Bombay inheritance
hh usually occurs in children of consanguineous marriages
Can be classic or para-bombay
Classic bombay
Can inherit ABO genes (written with superscripts)
Para-bombay
Rare; mutated FUT1 gene with or without FUT2
Mutation has the L-Fucose enzyme reduced that can have small traces of H, A, and B antigens (detected by elution)
Bombay red cell reactions
Fail to react with anti-a, anti-b, and anti-H
Bombay serum reactions
Contains anti-a, anti-b, anti-a,b , and anti-h (very potent and reacts at 37°)
Transfusion to Bombay individual
Normal O red cells would cause immediate lysis (IgM)
Only Bombay blood will be compatible
Bombay screening reactions
Screen and cross match: all reaction
Auto control: negative
A3 forward type reactions
Anti a: ++mf
Anti-b: 0
Anti-a,b: ++ mf
Anti-H: 3+
A3 reverse type reactions
Anti-A: no
Anti-B: yes
Anti-a1: sometimes
Substances present in saliva of A3
A,H
A3 number of antigen sites
35
Ax forward type reactions
Anti-a: wk/0
Anti-b: 0
Anti-a,b: 2+
Anti-h: 4+
Ax reverse type reactions
Anti-a: 0/wk
Anti-b: yes
Anti-a1: almost always
Substances in saliva of Ax
H
Ax antigen sites
5
Ay forward type reactions
Negative for all except anti-h
Ay reverse type reactions
Only anti-b +
Substances in saliva of Ay*
A and H*
Number of antigen sites in Ay
1
A(el) forward type
Same as Ay
A(el) reverse type
Anti-a: some
Anti-b: yes
Anti-a1: yes
Substances present in Ael saliva
H
Number of antigen sites for A(el)
0.7
B3 forward reaction
Anti-A: 0
Anti-b: ++mf
Anti-a,b: ++mf
Anti-h: 3+
B3 serum antibodies present
Anti-a
Substances present in saliva of B3
B and H