Suppressive factor against macrophage phagocytosis produced by cultured sarcoma-180 cells

A soluble factor which suppresses phagocytic ability of macrophages against Staphylococcus aureus, as well as latex particles, was found in the culture supernatant of sarcoma-180 cells. This factor was stable to heating at 56 degrees for 30 min and had a molecular weight of more than 10,000. Supernatant from normal spleen cell culture also showed some antiphagocytic activity but it was considerably lower than that of sarcoma-180 cell culture.