Immune response and the B blood group locus in chickens.

Chickens of three blood group genotypes, B1B1, B1B2 and B1B19, were compared in their ability to produce antibodies. The B locus is the major histocompatibility locus in this species. Homozygous B1 pullets had significantly higher adult mortality than did the B1 heterozygotes. In two separate experiments the B1B1 females produced significantly fewer antibodies to Salmonella pullorum than did the B1 heterozygotes. Also the B1B1 pullets responded with lower antibody titers following immunization with ferritin, bovine serum albumin and parainfluenza-3 virus, although the differences were not significant. The results of this study suggest that an immune response gene is associated with the major histocompatibility locus in chickens, paralleling the H-2 locus and Ir genes in mice.