Effect of recombinant interferon-gamma on protein content, phagocytic, and cytotoxic activity of mouse peritoneal macrophages.

We have studied the effect of recombinant murine interferon-gamma (rMuIFN-gamma) on the protein content, phagocytic activity, and cytotoxicity of mouse peritoneal macrophages (MPM). The aim of this study was to see whether rMuIFN-gamma alone could influence these parameters of MPM activity or if an additional stimulus, like elicitation or cultivation with lipopolysaccharide (LPS), was required. The MPM cultures were treated with rMuIFN-gamma for 24, 48, or 72 h. Generally, rMuIFN-gamma treatment of the cultures increased the protein content of the MPM. MPM were generally cytotoxic and they phagocytized IgG-opsonized Escherichia coli under the experimental conditions of this study. The effects of rMuIFN-gamma on phagocytic and cytotoxic activities were complex and highly dependent on the dose and length of treatment. Low or high concentrations may exert opposite effects on the same functions. Addition of a low dose of LPS to the cultures did not generally amplify the rMuIFN-gamma-induced alterations of MPM activities. However, the combination of LPS, high doses of rMuIFN-gamma, and long incubation time reduced the protein content, suppressed the phagocytic activity, and negatively influenced the viability of the MPM. Thioglycolate-elicited MPM had a higher baseline activity than resident MPM, but the rMuIFN-gamma effect on elicited MPM was parallel to the effect on resident MPM.