Concanavalin A stimulation of mouse lymphocytes at low concentration. I. The effect of peritoneal exudate cells.

The results presented here show that concanavalin A (Con A) stimulated mouse spleen lymphocytes cultured at 1/10th optimal concentration incorporated less [3H]-TdR than those cultured at the optimal concentration. It was possible to increase the response of 1/10th optimal concentration lymphocytes by supplementing the cultures with macrophage-rich peritoneal exudate cell (PEC) preparations. This effect was dependent on the PEC concentration. [3H]-TdR incorporation by lymphocytes at optimal concentration was inhibited by the addition of PEC to the cultures. Thymocyte cultures at 1/10th optimal concentration also showed increased [3H]-TdR incorporation when supplemented with PEC but there was no inhibition effect at optimal concentration. PEC which had been pretreated with fresh mitomycin C to prevent cell division were as effective as controls at promoting the stimulation of 1/10th optimal concentration lymphocytes. PEC which had been killed were much less effective than controls.