Dyscoordinate expression of tumor necrosis factor-alpha by human blood monocytes and alveolar macrophages.

Abstract

Previous studies have shown that human alveolar macrophages produce less interleukin-1 (IL-1) in response to lipopolysaccharide (LPS) than do their precursors, blood monocytes. The purpose of this study was to compare the capacities of alveolar macrophages and blood monocytes to synthesize tumor necrosis factor (TNF) in response to LPS. Alveolar macrophages were obtained by bronchoalveolar lavage of healthy nonsmoking subjects, and blood monocytes were obtained by adherence of mononuclear cells to plastic. TNF activity was measured in supernatants and cell lysates as cytotoxicity to L929 fibroblasts (uptake of neutral red at 570 nm). TNF activity of alveolar macrophages stimulated at 10(6) cells/ml with LPS (10 micrograms/ml) for 16 h was 596 +/- 367, and of blood monocytes it was 60 +/- 84 U/ml (mean +/- SD, p less than 0.005). At no concentration of LPS and at no period of stimulation did alveolar macrophages express less TNF activity than did blood monocytes. In concurrent experiments, supernatants of LPS-stimulated alveolar macrophages contained less IL-1 activity than did blood monocytes. Lysates of both cell types contained less than 20% of total TNF activity. The TNF activity of LPS-stimulated alveolar macrophages was neutralized greater than 99% by monoclonal antibody to TNF-alpha; control monoclonal antibody OKT3 had no effect. Next, alveolar macrophages and blood monocytes were biosynthetically labeled with [3H]leucine during incubation with LPS; supernatants were immunoprecipitated with anti-TNF, and precipitates were electrophoresed on polyacrylamide gels. Autoradiographs indicated that immunoreactive TNF was produced by both blood monocytes and alveolar macrophages and that the relative molecular weights were identical (17,000).(ABSTRACT TRUNCATED AT 250 WORDS)