Formation of germinal centres during neonatal tolerance in the chicken.

Chickens were made tolerant to BSA at the time of hatching. During the tolerance, antigenic stimulation with BSA resulted in poor germinal centre formation as compared to normal immunized control birds. The tolerance persisted for at least 6 weeks. Its breakdown had hardly started at the age of 12 weeks, both IgM and IgG antibody responses against BSA remaining negligible. Stimulation with the unrelated antigens SRBC and Brucella abortus resulted in good antibody responses, but the number of germinal centres was smaller in the tolerant birds than in normal controls.