Identification of Blood Group A Subgroups

While 80% of persons possessing blood group A are of group A1, 6 other subgroups of A substance may occur.

How encountered:

(1) unexpected anti-A activity (mismatch between front and back typings)

(2) weak or absent reaction with antisera

Method for evaluation:

(1) reaction of cells with specific antisera or with lectins having an activity mimicing an antisera

(2) reaction of sera with cells of known phenotype

(3) if the person is a secretor, the presence or absence of A substance in the saliva

cells with	A1	A-int	A2	A3
• anti-A	4+	4+	4+	2+ mixed field
• anti-A1 or lectin Dolichos diblorus	4+	2+	0	0
• anti-A,B	4+	4+	4+	2+ mixed field
• anti-B	0	0	0	0
• anti-H or lectin Eulex europaeus	0	3+	2+	3+
serum with
• A1 cells	0	0	0 to 4+	0 to 4+
• A2 cells	0	0	0	0
• B cells	4+	4+	4+	4+
• O cells	0	0	0	0
A substance in saliva of secretors?	Yes	Yes	Yes	Yes

where:

• anti-A1 may be present in 1-8% of patients with type A2 and 22-35% with type A2B.

• anti-A1 may rarely be found in patients with type A3 or A3B

• A person with type AB would show a reaction between cells and anti-B, while anti-B would not be in the sera.

cells with	Am	Ax	Ael
• anti-A	0 to +/-	0 to +/-	0
• anti-A1 or lectin Dolichos diblorus	0	0	0
• anti-A,B	0 to +/-	1+ to 2+	0
• anti-B	0	0	0
• anti-H or lectin Eulex europaeus	4+	4+	4+
serum with
• A1 cells	0	0 to 2+	0 to 2+
• A2 cells	0	0 to 1+	0
• B cells	4+	4+	4+
• O cells	0	0	0
A substance in saliva of secretors?	Yes	No	No

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