Interleukin-6, interferon-gamma, and phospholipid levels in the alveolar lining fluid of human lungs. Profiles in coal worker's pneumoconiosis and idiopathic pulmonary fibrosis.

Cytokines are widely involved in physiologic as well as immunoinflammatory and fibrosing processes of the lung. The aim of this work was to study, by bronchoalveolar lavage, two groups of human interstitial lung diseases (ILD) with fibrosing propensity (ie, idiopathic pulmonary fibrosis [IPF], n = 10; and coal worker's pneumoconiosis [CWP], n = 15). Patients were compared with nonsmoker control subjects (n = 20). Cellularity, proteins, and phospholipids were determined in the alveolar fluids. In addition, two cytokines (interleukin-6 [IL-6] and interferon-gamma [IFN-gamma]), which are presumed to possess respective antifibrotic and profibrotic activities, were measured in the respiratory tract. Compared with control subjects, IPF and simple CWP showed alveolar hypercellularity (p < 0.05) and relative lymphocytosis (p < 0.05). Both exhibited increased alveolar permeability (ie, increased albumin/urea ratio, p < 0.05), with enhanced IL-6 and decreased IFN-gamma in the alveolar spaces (p < 0.05). On the other hand, IPF displayed an associated polymorphonuclear alveolitis, enhanced alveolar epithelial lining fluid (AELF) volume and low surfactant phospholipid levels (p < 0.05 vs control), whereas simple CWP shared an exclusive lymphocytosis, normal AELF volume, and a surfactant lipid overflow (p < 0.05 vs control). Relationships among all of these parameters were found only between alveolar cellularity, neutrophils and IL-6 levels in the AELF of IPF (respectively, r = 0.85, p = 0.0009, and r = 0.89, p = 0.0006). In summary, common alterations of cellular and cytokine turnover were observed in IPF and simple CWP and may reflect activity of the antifibrotic fight in these diseased lungs. Surfactant phospholipid levels are likely to represent a specific disturbance among IPF and CWP, but no clear relationship with respect to the other parameters could be established for explaining the difference in time course outcome.