The bursal origin of an immunocompetent cell for antibody formation in the chicken.

Surgically bursectomized and irradiated chickens were given bursal, splenic, bone marrow or thymic cells taken from syngeneic donors, together with killed Brucella abortus and Salmonella pullorum. Blood samples were taken from those chickens 7 days later, and the serum agglutinin titres were determined. The cells of any lymphoid organ taken from 28-day-old chickens were more effective in restoring antibody response than those from 18-day-old ones. The restorative capacities of the bursa and splenic cells were greater than those of the bone marrow and thymic cells. On the other hand, splenic, bone marrow or thymic cells taken from bursa-less chickens, and lymphoid cells taken from normal chickens but treated with anti-bursa serum in the persence of complement, were virtually incapable of restoring the immune response. Bursal, splenic or bone marrow cells taken from neonatally thymectomized chickens, and bursal or thymic cells treated with anti-thymus serum were effective, being comparable with the corresponding cells taken from normal chickens or treated with normal sera, in restoring the suppressed immune response in chickens devoid of the lymphoid system. These facts clearly indicate that the primary and central agent crucial for development of the humoral immune response against the two bacterial antigens tested is the bursa. It is strongly suggested from the results of adoptive immunization using intrabursally primed cells that the cells recognizing Brucella abortus exist within the bursa of 4-day-old chicken.