STIMULATION OF BONE MARROW-DERIVED AND PERITONEAL-MACROPHAGES BY A LYMPHOCYTE-T-DERIVED HEMATOPOIETIC GROWTH-FACTOR, PERSISTING CELL-STIMULATING FACTOR

Abstract

Several lines of evidence indicated that P cell-stimulating factor (PSF), a T lymphocyte-derived lymphokine known to stimulate the growth of hemopoietic stem and progenitor cells, also acted in macrophages. PSF was absorbed from medium that had been mixed for two hours at 0.degree. C with either resident or thioglycolalte-elicited peritoneal cells, suggesting the presence of receptors for PSF on cells in the population. The addition of pure PSF to populations highly enriched in either resident or elicited adherent peritoneal macrophages resulted in stimulation of macrophages with morphological changes, including increases in size, spreading, vacuolation, and the number of cytoplasmic processes, together with stimulation of proliferation and the phagocytosis of opsonized yeast. PSF also stimulated the incorporation of [3H]thymidine by bone marrow-derived adherent macrophages. Addition of pure PSF to cultures that contained only a single macrophage resulted in enhanced survival and proliferation of these isolated cells, demonstrating that the effect of PSF on macrophages was direct. These results indicate that PSF can stimulate well-differentiated functional mcrophages and raise the possibility that the effects of PSF on macrophages may play a regulatory role in immune responses.