Suppressor function of peripheral blood mononuclear cells in normal individuals and in patients with systemic lupus erythematosus.

Normal peripheral blood mononuclear cells demonstrated increased DNA synthesis and secretion of newly synthesized protein when suboptimal concentrations of Concanavalin A (Con A) were added to the cultures after 24-h incubation in vitro. Cells stimulated by Con A, 1 mug/ml, after 24-h incubation demonstrated 3.0 times more tritiated thymidine incorporation, and 4.4 times more 14C-amino acid incorporation into newly synthesized secreted protein, than cells stimulated at 0 h (P less than 0.001). The acquisition of increased responsiveness was not abrogated by washing and resuspending the cells in fresh medium. Since the increased responsiveness could be inhibited by the addition to the cultures of small numbers of cells previously activated by Con A it is suggested that the enhanced reactivity acquired in culture represents the loss of a subpopulation of suppressor cells that modulate the T-lymphocyte response. Cells from nine patients with active, untreated systemic lupus erythematosus demonstrated normal responses to optimal concentrations of Con A added at 0 h, but an impaired response to Con A, 1 mug/ml. When these cells were incubated for 24 h, a significant increased response to Con A was not observed. This observation suggests that patients with active SLE lack circulating suppressor cells. When seven SLE patients were again studied after corticosteroid therapy had led to clinical improvement, the response to Con A, 1 mug/ml, added after 24-h incubation was similar to that observed in normal controls, suggesting that suppressor function in SLE returns as disease activity declines.