Autostimulatory factor produced by B-cell lines from patients with Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune disease with a predisposition to transform into a B-cell lymphoma. Stable B-cell lines were established (without exogenous stimulation other than fetal bovine serum) from the peripheral blood of three SS patients. These cell lines secreted immunoglobulin (either IgG, IgM or both) and expressed cytoplasmic immunoglobulin. They were positive for the B-cell markers Leu 12 and Leu 16, and also for HLA-DR and the transferrin receptor. The cells lacked CD3 and the IL-2 receptor. Supernatants from these cell lines had autostimulatory activity. When 24-h culture supernatants were added to freshly cultured peripheral blood mononuclear cells, the proliferation index was 2-3 times higher as compared to cells cultured with HB101 medium alone. This autostimulatory activity can be attributed to a B-cell growth factor since these supernatants were also able (1) to support the growth of BD9 cells and (2) to augment the proliferation of PB B cells preactivated with S. aureus Cowan strain I. Furthermore, the supernatants did not contain IL-1, IL-2, or gamma-interferon. Thus, B cells that grow spontaneously from the peripheral blood of SS patients spontaneously produce a B-cell growth factor. This factor could contribute importantly to the autoantibody production, tissue lymphoid infiltration and B-cell lymphoma seen in this disease.