Development of immunity against antigens of the A and B blood groups during postembryogenesis in chickens

51Cr-labelled erythrocytes were injected into young chicks, F1 hybrids of the inbred chicken lines, from hatching to 2 months of age. The onset of immunity was measured by means of elimination of labelled red blood cells. It was found that with the B-locus difference between donors and recipients the immune response developed from 4 days of age to the end of the first week, whereas with the A-locus difference it developed during the second week of life. The onset of immunity is delayed in inbred chickens compared to outbred chickens, because we have used one alloantigen difference.