Oestrogen is a potent immunomodulator of murine experimental rheumatoid disease.

Oestrogen has important modulatory effects on autoimmune diseases. Earlier studies, both in humans and in experimental models, have convincingly suggested that oestrogen exaggerates lupus disease and enhances autoantibody production in lupus. However, a general effect by oestrogen to stimulate auto-immune disease does not fit with recent findings in human rheumatoid arthritis and in certain experimental autoimmune models. Here it is shown that oestrogen treatment suppresses development of type II collagen induced arthritis in mice and rats, which is a T-cell dependent experimental model for human RA. The oestrogen-mediated effects are obtainable in physiological levels and both incidence and severity of disease can be suppressed. It is demonstrated that oestrogen has a dualistic effect on the immune system by suppressing antigen-specific T-cell dependent immune reactions while enhancing B-cell activities. On these grounds, we suggest that autoimmune diseases should be divided into two groups, one in which oestrogen accelerates disease progression and another in which oestrogen is beneficial.