Modulation by macrophages of lymphocyte responses to phytohaemagglutinin, concanavalin A and semiallogeneic cells.

To investigate the effect of macrophages on rat lymphocyte activation by phytohaemagglutinin (PHA), concanavalin A (Con A) and semiallogeneic cells (uniderectional MLR), increasing concentrations of peritoneal cells (PC) were added to cultures of lymph node lymphocytes. Lymph node cell preparations contained 2-4% esterase positive cells (macrophages/monocytes). Any additional PC seemed only to inhibit MLR, whereas optimal responses of PHA and Con A stimulated cultures occurred when 1-2% abd 3-7% PC respectively were added. Ten percent PC markedly inhibited the response of both PHA and Con A stimulated cultures when added for the last 24 h of incubation. Inhibitory cells were shown to belong to the glass-wool adherent population of PC.