Elevated circulating levels of interleukin-6 in patients with chronic renal failure

In a previous study, we demonstrated the presence of circulating interleukin-1 (IL-1) in long-term dialyzed patients and that of tumor necrosis factor alpha (TNF alpha) in both long-term and not yet dialyzed uremic patients. In the present study, we attempted to determine the respective influence of hemodialysis (HD) and uremia on the plasma level of interleukin-6 (IL-6), which shares several biological properties with IL-1 and TNF alpha, including the induction of the acute phase response of the inflammatory process. Forty-eight patients with end-stage renal failure, including 32 long-term HD patients and 16 chronic uremic patients undergoing their first dialysis session, were tested for plasma IL-6 using both biological and immunoreactive assays. Plasma IL-6 activity was significantly increased in patients with chronic renal failure (P less than 0.001) compared to its level in normal individuals. No difference was observed, however, between long-term and not yet dialyzed patients. In the patients with the most pronounced IL-6 activity, immunoreactive IL-6 levels between 60 and 150 pg/ml were detected. A monoclonal antibody (mAb) against human IL-6 inhibited the activity of plasma in the IL-6 bioassay, and a close correlation existed between the biological activity of IL-6 and its immunoreactive level. No change in plasma IL-6 was detected during the course of the first dialysis as well as subsequent sessions. Likewise, no influence of the nature (cellulosic or synthetic polyacrilonitrile) of the dialysis membrane equipping the dialyzer was observed.(ABSTRACT TRUNCATED AT 250 WORDS)