Macrophage suppression by a low-molecular-weight fraction of murine spleen cell culture supernatant


Macrophage suppression has been reported to be mediated by a component of murine serum. The present investigation involves in vitro production of this macrophage modulator (suppressor) by concanavalin A-stimulated murine spleen cells. Spleen cell culture supernatant containing this suppressor, which has been called macrophage suppressor factor (MSF), caused a significant decrease in in vitro phagocytosis of Listeria monocytogenes by resident murine peritoneal macrophages. The molecular weight of MSF was determined by ultrafiltration to be less than 10,000, and the suppressor activity of MSF was not altered by heating at 100 °C for 30 min or storage at -70 °C for 6 months. MSF is resistant to treatment with Pronase E, but is, however, sensitive to acid hydrolysis. Activity of MSF in spleen cell culture supernatants from normal mice does not differ from that in supernatants from mice immunized with L. monocytogenes. It was determined that MSF is not affected by antigenic stimulation and is apparently produced constitutively.



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Cellular Immunology