The endocrine role of the thymus and its hormone, thymosin, in the regulation of the growth and maturation of host immunological competence.

Abstract

This chapter describes the endocrine role of the thymus and its hormone, thymosin, in the regulation of the growth and maturation of host immunological competence. The essential role of thymosin, and perhaps of other thymic factors, in growth and development is reflected in the two established roles of the thymus gland. These are: (1) the provision in early postnatal life of lymphoid cells that are exported from the thymus to the peripheral lymphoid structures and which become a cell population that endows the neonatal organism with immunological competence, and (2) the secretion from thymic epithelial cells of one or more hormones, one of which is thymosin. These humoral factors apparently function by acting on both stem cells and thymus-derived cells to activate and/or depress a cell that has all the potential to function as a mature immunologically competent lymphocyte. In addition, thymosin may act to reverse aberrations of lymphoid cell functions, for example, proliferation of aberrant thymocytes.