Bursal fabricii as a peripheral lymphoid organ. Transport of various materials from the anal lips to the bursal lymphoid follicles with reference to its immunological importance.

In tracer studies, various particulate and molecular materials applied on the anal lips of chickens were transported to the bursal lumen. From here some of the tracers were further transported into the bursal lymphoid follicles and colloidal carbon even to the bursal stroma. In immunization experiments, Brucella abortus organisms and SRBC were applied on the anal lips of 1-day-old, 4-week-old and 10-week-old chicks on 5 consecutive days. Although Brucella bacteria in tracer studies were not found in the bursal tissue, agglutinin response to Brucella was observed in the 4-week and 10-week groups as early as 3 days after the last application of this antigen. The response to SRBC was strong only in the oldest group of chickens. When stimulated continuously, the agglutinin titres reached their highest values after the 2nd week and then began to decrease to rather low levels. In the youngest age group, the anti-SRBC titres, however, remained low during the whole experimental period, and even in the 4-week group the anti-SRBC response was weak. Bursectomy, carried out at the age of 10 weeks, inhibited the agglutinin response to Brucella but affected only little the response to SRBC. It is concluded that by taking up antigens per anum the chicken possibly gains part of its basic immunity. In this immune response the bursa seems to play an important role at least with some antigens, and thus the bursa may have an immunofunction comparable with that found in peripheral lymphoid organs.