THE EFFECTS OF THYMUS AND OTHER LYMPHOID ORGANS ENCLOSED IN MILLIPORE DIFFUSION CHAMBERS ON NEONATALLY THYMECTOMIZED MICE

Abstract

When neonatally thymectomized CBA mice were implanted at 9 to 12 days of age with Millipore diffusion chambers (pore size, 0.1 µ) containing either syngeneic or allogeneic neonatal thymus, they were subsequently found to have the capacity to reject skin homografts and to form antibodies to sheep erythrocytes. In spite of displaying restored immune reactivity, thymectomized mice bearing thymus-filled diffusion chambers still had a lymphopenia and diminished numbers of small lymphocytes in their spleens, lymph nodes and Peyer's patches. Comparison of the lymphoid organs of these mice with those of the thymectomized control mice did not reveal any appreciable difference in the numbers of primary follicles or small lymphocytes. It is postulated that the thymus humoral factor induced immunological competence in lymphoid cells which had left the thymus prior to neonatal thymectomy. The paucity of circulating and tissue small lymphocytes in thymectomized animals, the immune reactivity of which was restored by thymus tissue in diffusion chambers, argues against the theory that the thymus humoral factor has a lymphocytosis-stimulating effect.