Macrophages and resistance of tumors 6. The effects of supernatants from cultures of normal and tumor cells on phagocytosis.
Mouse resident peritoneal macrophages were cultured with supernatants from cultures of tumor cells and normal cells, then tested for their capacity to phagocytose opsonized sheep erythrocytes (SRBC). Most tumor cells produced inhibitory material but some did not (HeLa, EL-4). Conversely, nonmalignant cells generally did not produce active material though some (Chang B cells) did. Inhibition was not noticeable until after 13 hr contact with tumor supernatant and then became progressively more pronounced at 24 and 48 hr. Phagocytic capacity recovered only partially on reincubation with fresh medium. Inhibition was caused by material of approximate M.W. less than 1,000 (by membrane filtration), which also inhibited macrophage migration in vitro but had no effect on delayed-type hypersensitivity reactions or tumor growth in vivo. There was no species specificity and normal macrophages from various sources were susceptible, although activated or stimulated macrophages were wholly or partly resistant. Tumor carriage was associated with an initial decrease in phagocytic capacity of resident peritoneal macrophages, followed by an increase then a second decrease, although the cells remained susceptible to the inhibitory effect of tumor supernatant in vitro. Depression of phagocytosis was more marked in the presence of normal mouse serum and less marked in the presence of human serum than in the presence of fetal calf serum. Phagocytosis of zymosan and pinocytosis of colloidal gold by mouse macrophages were also depressed by tumor cell products.
D000818:Animals; D001202:Ascitic Fluid / Q000166:cytology; D002478:Cells, Cultured; D007108:Immune Tolerance; D007113:Immunity, Innate; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D009374:Neoplasms, Experimental / Q000276:immunology*; D010587:Phagocytosis; D010873:Pinocytosis; D013997:Time Factors