Auto-anti-A1: another cause of ABO discrepancy.

Anti-A1 was found in the serum of a patient of blood group A1 who had never received a blood transfusion. The patient's serum caused agglutination of his own red blood cells. The anti-A1 could be totally absorbed by red blood cells from the patient and from other A1 individuals. The anti-A1 was inhibitable by soluble group A-specific substance and was denatured by 2-mercaptoethanol. The A and H serum transferases were normal. The presence of auto-anti-A1 in the serum of an A1 individual is yet another cause of ABO discrepancy.