Effect of thymus enclosed in millipore diffusion envelopes on thymectomized hamsters.

yr HERE IS INCREASING EVIDENCE that the thymus has a central role in the development of the immune system.1’2 Surgical removal of the thymus in newborn mice and rats results in wasting, lymphocytopenia, and impaired immune responses.”2 Previous studies from our laboratory demonstrated that similar effects were also produced in hamsters subjected to neonatal thymectomy.3’4 The existence of a humoral thymic factor which maintains immune responsiveness has been suggested by the prevention of wasting disease and loss of immune competence iii thymectomized mice and rats implanted with cell-tight diffusion chambers containing thymus.5 #{176}’59 These animals with implanted diffusiomi chambers, however, still showed evidence of lymphocyte depletion even though humoral antibody responses and homograft rejection were largely intact.5’6’8’10’”59 The present report describes our studies on the effect of thymus and other tissues, enclosed in Milhipore diffusion envelopes, on thymectomized hamsters. Part of these studies have been previously pnesented. Our results indicate that a humoral substance, apparently specific to the thymus, was capable of maintaining a normal humoral antibody response in thymectomized hamsters. This humoral substance was apparently produced by thymic epithehial-neticular cells; it failed to maintain normal levels of blood lymphocytes.