Antibody-producing cells in chickens tolerant to human serum albumin

Cells forming antibodies to HSA were determined by the haemolytic plaque technique in the spleens of chickens in which tolerance to HSA was induced on the day of hatching. After immunization with HSA 2 weeks after hatching, no anti-HSA PFC or their very low numbers were observed in chickens rendered tolerant by the dose of 100 mg HSA. In a considerable proportion of the chickens, in which tolerance was induced by 1 mg or 0.1 mg of HSA, PFC were detected, though in statistically significantly lower numbers than in control birds. In tolerant chickens receiving 100 mg of HSA after hatching, the number of PFC after immunization at 4 weeks of age was statistically significantly and at 6 weeks non-significantly lower than in the controls. After immunization with BSA at 4 weeks of age, chickens injected with 100 mg HSA after hatching had the number of anti-HSA plaque-forming cells higher than the controls, but the difference was not statistically significant.