Effect of soluble interleukin-6 receptor α and interleukin-6 secreted by polymorphonuclear leukocytes on tumor necrosis factor-α expression and its production by peripheral blood mononuclear cells

Background: It has recently been shown that soluble interleukin-6 receptor (sIL-6R) alone or complexed with interleukin (IL)-6, besides their regulatory role in a wide variety of both normal and abnormal biologic reactions mediated by IL-6, could be an effective stimulator of the cell function.Aims: The key question of the present study is whether the sIL-6Rα or sIL-6R with IL-6 released by polymorphonuclear leukocytes (PMN) can influence cytokine secretion such as tumor necrosis factor-α (TNF-α) by peripheral blood mononuclear cells (PBMC), which together with PMN develop the inflammatory and immune response of a host.Methods: Cells were isolated from heparinized whole blood of healthy persons. The PMN were cultured for 1 h at 37°C in 5% CO2. After incubation, the culture supernatant of PMN was removed and was added to PBMC. The PBMC were cultured for 1 h at 37°C in the same conditions. In the culture supernatants and lysates of PMN, we examined the concentrations of sIL-6R by enzyme-linked immunosorbent assay (ELISA). TNF-α was measured at both protein and mRNA levels. Protein levels were determined by ELISA. To examine TNF-α mRNA expression, we isolated mRNA from PBMC after culture, using TRIZOL Reagent. The quantity of mRNA TNF-α was determined by the Quantikine mRNA assay.Results and conclusion: The results obtained revealed that sIL-6R with IL-6 secreted by PMN may play a regulatory role in the immune response by modulating the TNF-α expression and its production by PBMC. This may have a significant influence on an early phase of the inflammation and other reactions mediated by TNF-α.