Background: Activation of various cytokines, e.g. TNF alpha, IL-1 and/or IL-6 may play important role in the pathogenesis of renal vasculitis and lupus nephritis (LN). Systemic effects of these cytokines may be modulated by their circulating soluble receptors. Plasma levels of cytokine receptors may thus be also markers of the activation of these cytokines.
Methods and results: Plasma levels of TNF alpha, its soluble receptor p75 (sTNF-RII), IL-6 and soluble IL-6 receptor (sIL-6R) were measured using ELISA in 17 pts with ANCA-positive renal vasculitis (12 active-ANCA-A, 7 in remission ANCA-R), 9 pts with active lupus nephritis (LN) and 5 healthy subjects. Pts with LN had in comparison with controls increased plasma levels of TNF alpha, sTNF-RII, IL-6 and sIL-6R. Pts with ANCA-A had also in comparison with controls increased plasma levels of TNF alpha, sTNF-RII and sIL-6R, but plasma levels of IL-6 were not significantly increased dut to great standard deviation. Pts with ANCA-R had in comparison with controls increased plasma levels of sTNF-RII, but plasma levels of TNF alpha were in ANCA-R significantly lower than in ANCA-A. While the ratio TNF alpha/sTNF-RII was significantly lower in all groups of pts than in controls, the ratio IL-6R/sIL-6R was in comparison with controls significantly increased only in LN.
Conclusions: While increased plasma levels of TNF alpha may be nonspecific marker of the activity of ANCA-positive renal vasculitis and LN, plasma levels of sTNF-RII are increased also in pts with ANCA-positive renal vasculitis in remission. Increased plasma levels of sTNF-RII may interfere with systemic effects of TNF alpha, but may also prolong the lifetime of its active form. Plasma levels of sIL-6R are increased both in ANCA-A and in LN, but their increase is, however, much less pronounced than that of sTNF-RII and cannot effectively block systemic effects of IL-6.