Tumor necrosis factor (TNF) is an oncolytic peptide that may also exert many other biologic effects. Experimentally, immunologically activated mononuclear phagocytes stimulated with endotoxin (LPS) produce TNF, while resting mononuclear phagocytes stimulated with LPS produce little TNF. To date, the ability of human alveolar macrophages (AMs) to produce TNF has not been clearly delineated. As pulmonary sarcoidosis is a granulomatous inflammatory disorder characterized by immunologically activated AMs, we investigated the production of TNF by AMs obtained by bronchoalveolar lavage from 7 normal volunteers and 13 patients with pulmonary sarcoidosis. The AMs were cultured with and without LPS, and TNF production was assessed by an in vitro cytotoxicity assay. Unstimulated sarcoid and normal AMs produced little TNF, but LPS stimulation enhanced TNF production by both normal and sarcoid AMs. Furthermore, LPS-stimulated sarcoid AMs produced more TNF than normal AMs (84.9 +/- 16.7 versus 32.5 +/- 10.2 units/million cells, P less than 0.05). It is concluded that human AMs can produce TNF and that sarcoid AMs are primed and can produce significantly more TNF, compared with normal AMs.