Immunization of chickens via the bursa of Fabricius isolated from the rest of the gut-associated lymphoid tissue using four surgical techniques.

To study the role of the chicken bursa of Fabricius separately from the rest of the gut-associated lymphoid tissue (GALT), four operating methods were developed; these techniques are described in detail. Bursal function and immunological state of the operated chickens were assessed by applying colloidal carbon, Brucella abortus organism, and sheep red blood cells (SRBC) into the isolated bursa and then measuring the humoral immune responses. Closing the bursal duct, after administering antigens through it, was shown to be a reliable and reproducible method for immunizing chickens strictly via the bursal system. In this method, morphology and endocytosis of carbon in the isolated bursae were normal. Furthermore, the anti-Brucella titers did not significantly differ from those in the unoperated per anum immunized control chickens, whereas the response to SRBC was significantly lower (P less than .001) in the operated chickens compared with controls. Separation of the bursa from the rest of the GALT showed that the chicken bursa of Fabricius functions as a peripheral lymphoid organ; specific antibodies are formed against antigens introduced into the bursal lumen. The operating method also has confirmed that Brucella is a bursa-dependent antigen, but that SRBC need cooperation of the GALT to evolve a good humoral immune response.