ANTI-INTERLEUKIN-6 AND SOLUBLE INTERLEUKIN-6 RECEPTOR IN SYSTEMIC LUPUS-ERYTHEMATOSUS

IL-6, soluble IL-6 receptor and IgG with anti-IL-6 activity were measu red in the plasma of 14 lupus patients and 10 normal subjects. The cap acity of peripheral blood mononuclear cells to spontaneously produce I L-6 in vitro was also measured. Our results indicate that IL-6 plasma levels in patient plasma as measured by ELISA were not different from normal but that supernatant levels were significantly lower than norma l (P < 0.05). In vitro IgG production was comparable for all lupus pat ients' cells irrespective of the in vitro IL-6 levels. Plasma soluble IL-6 receptor levels directly correlated with IL-6 production capacity of SLE cells and the ratio of soluble receptor to anti-IL-6 directly correlated with IL-6 production in patients but not in normals. Inhibi tion assays demonstrated competition between anti-IL-6 and soluble rec eptors for IL-6 and the inhibition by plasma of IL-6 binding to monocl onal anti-IL-6. We believe the interaction of anti-IL-6 and IL-6 recep tor with IL-6 may contribute to the homeostasis in IL-6 activity in vi vo and skewing of the soluble receptor/anti-IL-6 ration may contribute to the lupus disease process.