ENHANCED PRODUCTION OF IL-1-RECEPTOR ANTAGONIST BY ALVEOLAR MACROPHAGES FROM PATIENTS WITH INTERSTITIAL LUNG-DISEASE

Alveolar macrophages (AM) produce various inflammatory and immunomodulatory cytokines. The objective of these experiments was to evaluate the production of IL-1ra, a specific receptor antagonist of IL-1, by AM from nonsmoking control subjects (n = 9), smoking control subjects (n = 6), and patients with interstitial lung disease (ILD) (n = 9). IL-1ra protein levels in cultured AM lysates and supernatants were determined by a specific ELISA; relative steady-state IL-1ra mRNA levels were measured using a specific cDNA probe. Before culture the isolated AM from all subject groups contained undetectable IL-1ra mRNA and no IL-1ra protein in the cell lysates as determined by ELISA. AM from nonsmoking control subjects spontaneously produced IL-1ra protein after a 20 h culture in medium, almost-equal-to 12 ng/ml with around half in cell lysates. AM from smoking control subjects produced levels of IL-1ra that were similar to the levels in AM from nonsmokers. In contrast, AM from nonsmoking ILD patients (n = 6) produced high levels of IL-1ra spontaneously (almost-equal-to 28 ng/ml), with no enhancement observed when cultured on adherent IgG. Interestingly, AM from smoking ILD patients (n = 3) produced lower levels of IL-1ra protein (almost-equal-to 11 ng/ml) that were comparable to levels noted in smoking control subjects. AM from all three types of subjects produced decreased amounts of IL-1ra in response to LPS and enhanced amounts in response to GM-CSF. In general, IL-1ra steady-state mRNA levels correlated with protein production. The IL-1ra found in ILD AM supernatants was 20 to 24 kD by western blot analysis and was biologically active. These results indicate that AM produce large amounts of IL-1ra spontaneously in culture. The enhanced production of IL-1ra by AM f rom nonsmoking ILD patients suggests that these cells may be primed in vivo to produce augmented levels of this cytokine.