Similar serum levels of IL-6 and its soluble receptors in patients with HCV-related arthritis and rheumatoid arthritis: a pilot study.

The high serum levels of Interleukin-6 (IL-6) and its soluble receptors (sIL-6r and sgp130), described in the course of Rheumatoid Arthritis (RA), have been linked to the enhanced activity of this cytokine in this disorder. In this study, the serum concentrations of IL-6 and its soluble receptors were determined in a group of patients with HCV-related arthritis (HCVrA), a condition resembling RA in several aspects, and then compared to those found in a sample of subjects affected by RA. Twenty-one patients with HCVrA, 24 patients with RA and 20 healthy subjects (control group) were examined. Different ELISA methods were used for determination of serum concentrations of IL-6, sIL-6r and sgp130. Increased IL-6 serum levels were found in 15 (71 %) of the patients with HCVrA and in 16 (62 %) of those with RA. Eight (38 %) of the patients with HCVrA and 11 (46%) of those with RA denoted high levels of sIL-6r, while sgp130 levels were elevated in 21 (76%) of the patients with HCVrA and in 16 (69%) of those with RA. A significant difference between the median values of sIL-6r and sgp130 levels in the two groups of patients versus controls was found. A mild correlation of these parameters with RF levels was detected in the RA group. Furthermore, in HCVrA patients the serum levels of IL-6, sIL-6r and sgp130 appeared unrelated to HCV viraemia and to levels of transaminases. The enhanced serum levels of IL-6 in HCVra patients indicate an increased synthesis and hyperactivity of this cytokine in HCVrA, and the substantial similarity of the behaviour of IL-6 and its serum receptors in the two groups of patients suggests common mechanisms with RA, in which the function of I L-6 is central.