Estrogen-induced suppression of collagen arthritis. III. Adult thymectomy does not affect the course of arthritis or the estrogen-mediated suppression of T-cell immunity.

Type II collagen-induced arthritis is dependent on the activation of T-helper cells and is modulated by female sex hormones. It is shown that treatment of castrated female DBA/1 mice with beta-estradiol decreases the incidence (32% vs 88%) as well as the severity of the disease. The estrogen-induced suppression of both the development of collagen arthritis and T-cell immunity were not dependent on the thymus. Thus, estrogen treatment of thymectomized and castrated female mice suppressed the incidence (21% versus 100% in controls) and severity of arthritis. Similarly, estrogen treatment of thymectomized and castrated female mice suppressed both antigen-specific delayed-type hypersensitivity and T-cell proliferative responses. These data suggest that the estrogen-mediated suppression of arthritis and T-cell immunity is not dependent on the presence of an intact thymus.