Cytokine‐independent progression of immunoglobulin production in vitro by B lymphocytes from patients with systemic lupus erythematosus

SUMMARY B lymphocytes from patients with systemic lupus erythematosus (SLE) secreted high levels of immunoglobulin spontaneously when cultured in vitro. Addition of the cytokines interleukin‐2, interleukin‐4 and interleukin‐6 either alone or in combination failed to augment spontaneous immunoglobulin synthesis. Percoll‐separated low‐density SLE B lymphocytes matured into immunoglobulin‐secreting cells also independent of exogenous interleukins. During maturation these cells became enlarged and less dense, and began to express CD23. This was in contrast to normal B cells, which did not secrete immunoglobulin spontaneously but synthesized IgM after interleukin stimulation. These results indicate that in vitro immunoglobulin synthesis by SLE B cells is already initiated in these cells and progresses independently of further stimulatory manoeuvres.