Effect of Adult Thymectomy on Immune Potentials, Endocrine Organs and Tumor Incidence in Long-Lived Mice

Abstract

The thymus is known to be a central lymphoid tissue playing an important role in the ontogenic development of the immune system. Neonatal thymectomy causes severe immunodeficiency in mice, which usually die from wasting disease in the conventional environment (1). In contrast, thymectomy performed at the adult state results in no immediate effect on the immune potentials of the mice (2). However, since the thymic functions to promote T cell-differentiation are known to be maintained in the thymus of mice of any age, although these functions decline progressively with age (3), it would be expected that removal of the adult thymus would result in a delayed impairment of T cell-dependent immune potentials (4,5). The T celldependent component of the immune system is also said to play an important role in immune surveillance (6) If so, the incidence of naturally occurring tumors would increase in adult thymectomized mice. Moreover, growth and involution of the thymus is said to be closely interrelated with normal function of the other endocrine organs (7). If so, adult thymectomy would also influence the function of the other endocrine organs.