Activated T cells in the synovial fluid of arthritic patients. II. In vitro activation of the autologous blood lymphocytes.

Lymphocytes isolated from the synovial fluid of arthritic patients were shown to express characteristics of immunoactivated T cells, such as the formation of stable E rosettes and natural attachment to normal and malignant cells. During 5 days incubation in autologous serum, the synovial T cells reverted to resting state. If, however, the synovial serum was present in the culture, the activated state was maintained. The blood lymphocytes of these patients did not have the markers of activation. When blood lymphocytes were mixed in vitro with the autologous synovial T cells, a proportion of them acquired the capacity to form stable E rosettes and to express natural attachment. Synovial polymorphonuclear cells or synovial serum were without effect on the blood lymphocytes. This phenomenon may represent an in vivo mechanism for the perpetuation of the cellular immune reactivity in the joint cavity.