Characterization of a B cell-derived growth-enhancing factor produced by a human B cell line established from a patient with rheumatoid arthritis.

A human B cell line, TKS-1, which was established from the peripheral blood of a patient with rheumatoid arthritis, was found to spontaneously produce a factor which enhances the activity of interleukin 1 (IL-1). This factor, designated B cell-derived growth-enhancing factor (BGEF), enhanced IL-1-induced proliferation of peanut agglutinin nonagglutinated thymocytes. BGEF also enhanced IL-1-induced production of interleukin 2 (IL-2) by both thymocytes and a human T cell clone, HSB.2 C5B2. BGEF alone did not induce the production of IL-2. BGEF failed to induce proliferation of the IL-2-dependent T cell clone, and did not enhance its response to IL-2. The activity of BGEF was not blocked by antisera against human IL-1-alpha or human IL-1-beta. Gel filtration analysis revealed that BGEF has a m.w. of 60,000 to 65,000 in its native state. We concluded that BGEF differed from IL-1 and IL-2, but is a novel factor produced by TKS-1 cells. In addition, we found that partially purified B cells from patients with rheumatoid arthritis produced factors which enhanced the activity of IL-1.