Interleukin 6 and its soluble receptor are elevated in aqueous humor of patients with uveitis

Purpose: To determine the levels of interleukin 6 (IL-6) and its soluble re ceptor (sIL-6R) in the aqueous humor (AH) of patients with different uveiti s entities. Patients and methods: AH and serum samples were collected from 35 patients (39 eyes) who underwent surgery for uveitis complications and f rom 10 controls (senile cataract). In the studied group, seven patients had HLA-B27(+) anterior uveitis, two had Fuchs' heterochromic iridocyclitis, 1 2 had chronic anterior uveitis of unknown etiology, and in the remaining 14 the causative agent was exogenous. The cytokine and receptor levels were m easured by enzyme-linked immunosorbent assay (ELISA). Results: In controls, the median IL-6 level in AH was higher than that in corresponding sera (40 .4 pg/ml and 5.2 pg/ml, respectively). In contrast, sIL-6R showed an invers e relation: there were less sIL-6R in control AH than in control sera (378. 9 pg/ml and 52749.0 pg/ml, respectively). The same qualitative relationship was observed in patients with uveitis. Quantitatively, in comparison to co ntrols, elevated levels of IL-6 and sIL-6R were found in AH of patients wit h uveitis. As expected, the maximal IL-6 and sIL-6R values were observed in the patients with uveitis of exogenous etiology (1558.3 and 1326.2 pg/ml, respectively). sIL-6R was also significantly elevated in AH of patients wit h HLA-B27(+) anterior uveitis (p<0.01). In all individuals under study, sIL -6R levels in AH samples were 2-10 times higher than IL-6 levels. Tn serum samples, sIL-6R level were 10000 times higher than corresponding IL-6 value s. Conclusion: The results confirmed the role of IL-6 in intraocular inflam mation and gave new information regarding the presence of its sR in normal and inflamed eyes. Low levels of sIL-6R in AH compared to those found in se rum suggest the presence of active local regulatory mechanisms that require further investigation.