P1 incompatibility in pigeon breeders.

Pigeon breeders of the P2 blood phenotype may develop anti-P1 haemagglutinins as a consequence of natural immunization to pigeon dust. The half-life of labelled P1 erythrocytes was determined in two P2 pigeon breeders otherwise compatible except for the presence of anti-P1 antibodies and in four compatible controls without anti-P1. The half-life of tagged cells was within the normal range in one breeder but significantly reduced in the other, indicating that P1 incompatibility may occur in vivo. Since anti-P1 antibodies are found in about 20% of P2 pigeon breeders, it is suggested that this group may be prone to developing an incompatibility to transfused P1 red cells.