HUMAN MONOCYTE AND MACROPHAGE MODULATION OF LYMPHOCYTE-PROLIFERATION

The effects of human monocytes and mature human macrophages on lymphocyte proliferation in response to PHA and allogeneic lymphocytes were examined. Monocytes enhanced and macrophages markedly suppressed lymphocyte proliferation to both stimuli. Monocyte enhancement of lymphocyte proliferation was, in part, due to a soluble mediator. Macrophage suppression was not due to (a) media depletion, (b) soluble lymphotoxins or inhibitors of proliferation, (c) media depletion, (d) macrophage production of prostaglandins, (e) decreased lymphocyte survival, or (f) induction of suppressor lymphocytes. These data emphasize the dichotomy of human monocyte and macrophage effects on lymphocyte proliferation and suggest, by exclusion, that macrophage suppression may require cell-cell contact. © 1979.