Modulation of human alveolar macrophage tumoricidal activity by C-reactive protein.

In previous reports, we have shown that purified human C-reactive protein (CRP) enhances tumoricidal activity of murine macrophages and human blood monocytes. In the present study, we wished to determine whether CRP induced similar activity in human macrophages. We evaluated the effect of CRP on the generation of in vitro tumoricidal activity in alveolar macrophages from 24 normal volunteers, among whom 10 were smokers and 14 were nonsmokers. CRP, in concentrations comparable with those found in blood during acute inflammation, induced dose-dependent cytotoxicity in nonsmoker alveolar macrophages against tritiated thymidine-labeled human tumor cells. Tumoricidal responses of smoker and nonsmoker macrophages did not significantly differ after exposure to lipopolysaccharide although smoker responses tended to be lower. Responses to CRP, however, were significantly (p less than 0.01) depressed in smokers. These findings suggest that during acute inflammation, CRP may enhance the tumoricidal properties of human alveolar macrophages. Macrophage responsiveness to CRP, however, appears to be detrimentally affected by smoking.