ANDROGENS ACCELERATE THYMOCYTE APOPTOSIS

Mechanisms of androgen-induced thymic involution are largely undefined . We have found that significant decreases in thymic size occur 2-4 h after a dose of testosterone is administered to castrated male mice. T his rapid rate of change suggests a role for androgen-induced apoptosi s in modulating the size and composition of the thymus. Using thymic o rgan cultures to define these effects of androgens, me found that dihy drotestosterone treatment of thymus tissues from females or from castr ated males results in enhancement of thymocyte apoptosis. Intact (andr ogen-replete) or testicular feminization, Tfm/Y (androgen-resistant) m ice failed to show apoptotic change with androgen treatment, although the apoptotic response to glucocorticoids was present, suggesting a re quirement for a functional androgen receptor. Acceleration of thymocyt e apoptosis by androgens may mediate processes of thymocyte selection, with the potential to impart gender-specific characteristics on the p eripheral T cell repertoire.