Immunobiologic Role of the Bursa of Fabricius and Thymus in the Development of the Competence to Produce Serum Antibody in Chickens

Abstract

Groups of chickens which were surgically thymectomized or bursectomized immediately after hatching, or hormonally bursectomized by testosterone injection at an early embryonic stage, or thymo-bursectomized were used in an attempt to elucidate the immunobiologic roles of the bursa of Fabricius and the thymus of the chicken in the initial development of immunologic competence, particularly the ability to produce serum antibody. There were no significant differences in the rate of elimination of an injected antigen (¹³¹ I-human serum albumin) from the blood of all the groups. However, a significant difference was observed in antibody production; no antibody was produced in the sera of hormonally bursectomized birds after the primary and secondary injections, while there was recognizable production of antibody in the sera of surgically thymectomized or bursectomized birds. Further, no antibody production was observed in tissue cultures of spleen cells derived from hormonally bursectomized chickens after immunization with human serum albumin or sheep erythrocytes. The injection of viable cells of the bursa restored to a significant degree the impaired capacity to produce antibody in hormonally bursectomized and surgically thymectomized birds as well as surgically thymo-bursectomized birds, while cell-free extracts of the bursa could restore the capacity only in the latter group of birds. These results suggest that in the chicken, only the bursa is concerned in the development of immunologic competence as measured by the ability to produce serum antibodies. The main role of the bursa seems to be to provide the initial supply of lymphoid cells and, in addition, the production of a humoral factor which promotes the proliferation of lymphoid cells and their immunological maturity.