Gamma Globulin Production and Antibody Synthesis in Chickens bursectomized as Embryos

Abstract

DEVELOPMENT of the immunoglobulin producing system of cells is controlled by the avian bursa of Fabricius^1,2. Elucidation of the role of the bursa in developing immunological potential began with the discovery that surgical removal of this hindgut lymphoid organ in the newly hatched chicken prevents later development of normal antibody response³. Depression of antibody response is greatest when the bursa is removed immediately after hatching. After 8–10 weeks, bursectomy alone no longer has a demonstrable effect on antibody response⁴. It was discovered later that normal embryonic development of the bursa could be inhibited by testosterone or other androgens⁵. Chickens which are given testosterone during embryonic life are often even more immunologically deficient than chickens which are subjected to bursal removal at hatching. Chickens which are surgically or hormonally bursectomized have reduced numbers of plasma cells and decreased levels of circulating gamma globulin. Near lethal whole body irradiation of newly hatched chicks in addition to bursectomy completely prevents later development of germinal centres and plasma cells and such chickens are agammaglobulinaemic^6,7. Germinal centres, plasma cells and immunoglobulin synthesis can be restored in bursectomized-irradiated chicks by injection of their unirradiated bursal lymphocytes⁸. These observations suggest that the bursa could be the only source of the germinal centre and plasma cell line but that some radiosensitive bursal cells leave the bursa before hatching.