Increased spontaneous interleukin-10 release from alveolar macrophages in active pulmonary sarcoidosis

The study was designed to determine whether alveolar macrophages (AM) in acute pulmonary sarcoidosis release in vitro the anti-inflammatory cytokine interleukin (IL)-10. To learn more about the coherence between IL-10 and proinflammatory cytokines in active sarcoidosis, the release of interferon (IFN)-gamma, macrophage inhibitory protein (MIP)-1alpha, and granulocyte-macrophage colony-stimulating factor (GM-CSF) was studied and additionally compared to normal controls and patients with pneumonia and interstitial lung fibrosis. AM were obtained by bronchoalveolar lavage from 13 patients with active sarcoidosis, 8 patients with interstitial lung fibrosis, 10 patients with bacterial pneumonia, and 14 normal controls. The spontaneous and stimulated (tumor necrosis factor [TNF]-alpha, IL-1beta) cytokine release was measured in the supernatant of cultured AM by enzyme-linked immunosorbent assay (ELISA). Unstimulated AM from sarcoidosis patients released more IL-10, IFN-gamma, MIP-1alpha, and GM-CSF than normal controls and patients with pneumonia and interstitial lung disease. Stimulation with TNF-alpha or IL-1beta increased the MIP-1alpha and GM-CSF release from AM of normal controls and patients with pneumonia and interstitial lung disease: however, no further enhancement of MIP-1alpha and GM-CSF production was observed in AM from sarcoidosis patients. Exogenous IL-10 reduced the spontaneous and stimulated MIP-1alpha and GM-CSF release in sarcoidosis to a lesser extent than in controls and patients with fibrosis and pneumonia. The up-regulated IL-10 in active pulmonary sarcoidosis may be a compensatory response to the enhanced expression of proinflammatory cytokines in order to down-regulate the inflammatory process. The results suggest an involvement of the anti-inflammatory cytokine IL-10 in the immunopathogenesis of sarcoidosis.