IMMUNE-COMPLEXES INCREASE NITRIC-OXIDE PRODUCTION BY INTERFERON-GAMMA-STIMULATED MURINE MACROPHAGE-LIKE JT74.16 CELLS

Murine macrophage-like J774.16 cells were tested for changes in nitric oxide production upon incubation with immune complexes, Cryptococcus neoformans capsular polysaccharide and polysaccharide-specific monoclo nal antibodies were added to J774.16 cells in the presence and absence of recombinant murine interferon-gamma (IFN-gamma). The effect of imm une complexes on nitrite synthesis was both concentration dependent an d isotype dependent. In the presence of IFN-gamma, immune complexes of IgG1, IgG2a, IgG2b, or IgG3 isotype increased nitrite levels, whereas complexes of IgM isotype did not, Immune complexes did not alter nitr ite production by unstimulated macrophages. Antibody alone, antigen al one, and antigen with irrelevant IgG1 antibody did not augment nitrite formation, either in the presence or absence of IFN-gamma, indicating a requirement for Fc gamma R cross-linking, These results suggest tha t IgG isotypes may offer additional protection against pathogens by en hancing macrophage nitric oxide production.