Allogeneic suppression of polyclonal immunoglobulin production in normals and patients with systemic lupus erythematosus

T lymphocytes suppressing in vitro polyclonal immunoglobulin production can be activated by allogeneic stimuli or concanavalin A (Con A). These cells are deficient in systemic lupus erythematosus (SLE). In order to investigate the cellular requirements for this effect, we studied IgM and IgG biosynthesis by (a) normal and SLE lymphocytes cultured with pokeweed mitogen (PWM) and mitomycin C-blocked allogeneic normal or SLE lymphocytes, and (b) by normal and irradiated lymphocytes cultured with PWM and with Con A-pretreated normal and irradiated allogeneic and autochthonous blocked lymphocytes. Results showed that blocked allogeneic normal cells or blocked Con A-pretreated, normal or irradiated, autochthonous or allogeneic cells served as potent stimuli for suppression of immunoglobulin biosynthesis by normal responder cells, but not by SLE responder cells. This suggests that Con A stimulates a radioresistant suppressor inducer cell which in turn activates a radiosensitive, proliferation-dependent suppressor effector cell; the latter can also be activated by allogeneic stimulation and is deficient in SLE.