A new, simplified assay for suppressor cell function.

A simplified, sensitive assay has been devised to examine suppressor cell function in normal persons and patients with rheumatic and atopic diseases. Cultured human lymphoblastoid (IM9) cells were used as responders. Induced suppressor cells were treated initially with mitomycin (mit) C, to prevent DNA synthesis, then incubated with concanavalin (con) A in microtiter plates for 40 hr. Responder cells were added directly to suppressor cells in plates. Suppression was determined by comparing effects of con A-induced with noninduced (control) cells on responder 3H-thymidine (3HTdR) uptake. This assay is simple and conserves time, reagents, and cells and uses standardized, available responder cells. It also obviates problems of con A in cultures with responder cells and autologous or allogeneic mixed-lymphocyte types of reactions and reduces needs for blood donation. Moreover, IM9 cells proved suitable for detecting spontaneous, con A-generated, glass-adherent, or prostaglandin-secreting (indomethacin-sensitive) suppressor cells.