Activation of human T and non-T lymphocytes by sepharose-bound concanavalin A and the differential effect of macrophages.

The mitogenic effect of insoluble concanavalin A (Con A) bound to Sepharose beads on human peripheral blood mononuclear cells has been investigated. Sepharose-Con A, with a maximum activity at 100-400 micrograms/ml and an optimal incubation time of 3 or 4 days, stimulated the mononuclear cells with a high mitogenic response. Sepharose-Con A also stimulated the monocyte-depleted lymphocytes and their T- and non T-enriched fractions with a definite mitogenic response, although the levels of response were much lower than those of unpurified mononuclear cells. Addition of the adherent monocytes strongly augmented the Sepharose-Con A responses of monocyte-depleted lymphocytes and their T-enriched fractions, whereas it gave no effect on those of non-T-enriched fractions. Culture fluids of adherent monocytes also augmented the Sepharose-Con A responses of monocyte-depleted lymphocytes. These results indicate that, although insoluble Sepharose-Con A activates both human T and B cells, the response of T cells but not B cells may be dependent in part on the presence of monocytes or a monocyte-derived soluble factor(s). Thus, it is concluded that Sepharose-Con A may be a useful mitogen to elucidate the role of macrophages or their soluble factors in activation of human T and B cells.