Macrophage regulation of mitogen-induced blastogenesis: I. Demonstration of inhibitory cells in the spleens and peritoneal exudates of mice

Abstract

Mitogen-induced blastogenesis of mouse B- and T-lymphocytes was inhibited by adherent spleen cells from normal or immunomodulator-treated mice. Blastogenesis could be similarly inhibited by the addition of syngeneic peritoneal exudate cells (PEC) from either normal or immunomodulator-treated mice suggesting a regulatory role for macrophages in lymphoproliferation. An adherent subpopulation of PEC (macrophages) was demonstrated to mediate inhibition of blastogenesis. Adherent PEC cells from immunomodulator (pyran copolymer)-treated mice had greater inhibitory activity than comparable cells from normal mice. Moreover, T-lymphocyte blastogenesis was more resistant to macrophage regulation than B-lymphocyte blastogenesis. Significant inhibition of blastogenesis could be demonstrated when ϑ -bearing cells were removed prior to the addition of PEC to cultures of spleen cells. Addition of nonadherent PEC to cultures of spleen cells was demonstrated to result in enhancement rather than inhibition of blastogenesis. Macrophage-mediated inhibition of blastogenesis was not merely the result of the potentiation of the effect of suppressive splenic macrophages since PEC were found to inhibit the response of adherence-depleted spleen cells even more than that of whole spleen cells.