Autostimulatory growth factors produced by Sjögren's syndrome B cell lines

Sjögren's syndrome (SS) is a systemic autoimmune disorder characterized by polyclonal hypergammaglobulinemia, autoantibody formation, and intense tissue infiltration by lymphoid and plasma cells. These patients have a predisposition to the development of monoclonal immunoglobulins and B cell lymphomas. To study the role of B cells in this disease, we established B cell lines from three patients with benign primary SS. These B cell lines grew spontaneously without any stimulation and expressed EBV nuclear antigen. The lines secreted an autostimulatory factor which had properties of a B cell growth factor. Peripheral blood B cells from SS patients, after culture for 3 days, secreted a similar factor which stimulated the proliferation of established SS B cell lines. These results suggest that circulating B cells in SS produce an autocrine growth factor that may contribute to lymphoproliferation and ultimately to the emergence of B cell lymphomas.