Competition between concanavalin A-induced stimulatory and inhibitory effects in the in vitro immune response to antigen.

The humoral response of nude spleen cells (b cells) to sheep erythrocytes was measured in the presence of varying numbers of concanavalin A (ConA)-acvated stimulatory spleen T cells (helper) and Con A-activated inhibitory spleen T cells (suppressor) from BDF1 mice. It was found that suppressive effects could be reversed by the presence of additional numbers of stimulatory cells. These results seem incompatible with the hypothesis that suppression is mediated by supraoptimal numbers of stimulatory cells and provides additional evidence that separate populations of T cells mediate stimulation and suppression.