Functional lymphocytes in the chicken pineal gland

The primary antibody response of lymphoid tissue occupying the pineal gland of 6-wk-old chickens was studied subsequent to injection of the carotid artery with sheep red blood cells (SRBC) or bovine serum albumin (BSA). Injection of SRBC did not produce plaque-forming cells (PFC) among pineal lymphocytes whereas BSA stimulated synthesis of anti-BSA immunoglobulin in pineal lymphoid tissue. A cytotoxic assay using appropriate anti-lymphocyte sera indicated that single-cell suspensions of pineal lymphocytes were composed of 42% B lymphocytes and 51% T lymphocytes. Bursal and thymic lymphocytes labeled with tritiated thymidine migrated into pineal lymphoid tissue when injected into 4- and 5-wk-old naive chicks. These observations indicate that the bursa and thymus make equivalent contributions to the lymphoid mass in the chicken pineal gland. Challenge of pineal-established lymphocytes by antigen introduced via the blood vascular system suggests that soluble antigens--rather than particulate ones--stimulate antibody production in the pineal gland. Collectively, these studies indicate that the pineal gland should be considered as a functional component of the chicken's lymphomyeloid system.