Serum levels of tumor necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6), and their soluble receptors in coal workers' pneumoconiosis.

The aim of this study was to investigate whether systemic tumor necrosis factor alpha (TNF-alpha), soluble TNF-alpha receptors (p55, p75), interleukin 6 (IL-6), and soluble IL-6 receptor could be markers of biological activities of coal workers' pneumoconiosis (CWP). The study population was composed of 182 Chinese retired coal miners who had similar dust exposure histories. Among them, 71 were cases with CWP and 111 were controls. Chest radiographs were classified according to International Labour Organization Criteria (ILO, 1980). Individual dust exposure variables were estimated from work histories, and smoking information was obtained from interviews. Serum concentrations of TNF-alpha, TNF-alpha receptors (p55, p75), IL-6, and IL-6 receptor were measured by ELISA techniques. Mean serum levels of p55, p75 and IL-6 were significantly higher in cases than in controls (P < or = 0.01 for each comparison by crude analyses). Results from logistic regression models, adjusted for age, dust exposure variables, and smoking habits, found similar associations between soluble p55 and p75 levels and the presence of CWP. Linear regression analysis revealed that CWP radiographic stage (by ILO criteria) was significantly correlated with the individual serum concentrations of p55, p75 and IL-6. Serum concentrations of all measured cytokines were notcorrelated to age, dust exposure, or smoking, but there were correlations between soluble p75 and p55 levels, and between p75 and IL-6 levels. The results of this study suggest that serum levels of TNF receptors and IL-6 are associated with the fibrotic process of CWP and serum cytokine levels may be correlated with the severity of CWP.