Compartmentalization of pro-inflammatory cytokines in tuberculous pleurisy

Abstract Increased levels of interleukin-6 (IL-6) and IL-8 are found in various immunologically mediated inflammatory disorders. Concentrations of IL-6, IL-8 and the soluble form of the IL-6 receptor (sIL-6R) were determined in serum and effusion fluid of 25 patients with tuberculous pleurisy utilizing enzyme linked immunosorbent assays (EIA). Serum IL-6 levels were only slightly increased in patients with tuberculous pleurisy in comparison to controls (11·1 ± 2·1 vs 7·3 ± 1·0 pg ml −1 ). IL-8 could not be detected in the serum of tuberculosis patients, but it was detected in the serum of healthy controls (8·0 ± 1·5 pg ml −1 ). In comparison to serum, IL-6 and IL-8 were found in high concentrations in pleural effusions (IL-6: 932 ± 70 vs 11·1 ± 2·1 pg ml −1 , P −1 ). In contrast, sIL-6R concentrations were much higher in serum compared to pleural effusion levels [30 477 ± 1905 vs 9881 ± 1177 pg ml −1 , P sem )]. The authors conclude that elevated levels of IL-6 and IL-8 in pleural effusions are compartmentalized at the site of active disease. The low levels of sIL-6R in the presence of high levels of IL-6 in pleural effusions, and the high levels of sIL-6R in the presence of low levels of IL-6 in serum suggest that the expression or shedding of sIL-6R may be downregulated in the presence of excessive amounts of IL-6.