Estrogen induced suppression of collagen arthritis. V: Physiological level of estrogen in DBA/1 mice is therapeutic on established arthritis, suppresses anti-type II collagen T-cell dependent immunity and stimulates polyclonal B-cell activity.

Immunization of castrated female DBA/1 mice with rat type II collagen (CII) induces severe polyarthritis with an onset 3-5 weeks after immunization and with 80-100% incidence. Estrogen treatment, inducing physiological 17 beta-estradiol (E2) levels, during a limited period before and after the immunization, or during another period before the expected onset of arthritis, delayed the arthritic onset by approximately 10 days but did not affect the incidence of severity of arthritis. Treatment with physiological doses of E2 after onset of arthritis decreased severity and duration of disease. The T-cell dependent anti-CII autoantibody response was suppressed if the E2 treatment was given immediately before and after CII immunization and was not significantly affected if E2 treatment was given after CII immunization. Neither the total anti-CII Ig levels nor the anti-CII IgG2a levels correlated with development of arthritis. We also titrated the serum levels of estrogen and recorded the vaginal smear response after injections of various doses of E2. This enabled us to work in a physiological range of estrogen levels, spanning the levels found at the end of pregnancy and those found during the normal estrous cycle. These levels were found to suppress antigen-specific T-cell functions but enhance certain B-cell activities since the delayed type hypersensitivity (DTH) reaction against CII was suppressed while the total number of splenic Ig-secreting cells increased. These findings suggest that estrogen in physiological doses is therapeutic for the development of collagen-induced arthritis and that estrogen exerts dualistic effects on the immune system by suppressing T-cell functions and stimulating certain B-cell activities. The suppressive effect on arthritis could not be explained by suppression of anti-CII autoantibody response and must therefore depend on other T-cell-mediated functions.