UP-REGULATION OF CYTOKINE RECEPTORS STNF-R55, STNF-R75, AND SIL-2R INPSORIATIC-ARTHRITIS SYNOVIAL-FLUID

Objective. To assess differences in soluble tumor necrosis factor rece ptor 55 (sTNF-R55), sTNF-R75, and soluble interleukin 2 receptor (sIL- 2R) in synovial fluid (SF) of patients with psoriatic arthritis (PsA), a seronegative inflammatory joint disease, in comparison with those o f patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Met hods. sIL-R were measured in SF with commercial sandwich ELISA and the results correlated with serological and clinical disease activity var iables. Results. In PsA SF the level of sTNF-R55 was 11.8 +/- 0.8 ng/m l and that of sTNF-R75 13.0 +/- 1.3 ng/ml. sIL-2R concentration in PsA SF was 800 +/- 84 U/ml. Compared to PsA SF, cytokine receptor levels in OA SF were significantly lower: 8.7 +/- 0.8 ng/ml for sTNF-R55 (p < 0.02); 7.1 +/- 0.9 ng/ml for sTNF-R75 (p < 0.0003); and 505 +/- 53 U/ ml for sIL-2R (p < 0.009). In contrast RA SF cytokine receptor levels were even higher than those of PsA SF (sTNF-R55: 18.1 +/- 2.0 ng/ml, p < 0.04; sTNF-R75: 29.5 +/- 2.9 ng/ml, p < 0.0002; and for sIL-2R: 195 7 +/- 290 U/ml, p < 0.03). Conclusion. In PsA SF sTNF-R55, sTNF-R75, a nd sIL-2R are upregulated compared to OA SF but are lower than in RA S F. Our results for TNF-R agree with recent findings in PsA, since TNF- alpha, an important stimulator for TNF-R, is also significantly lower in PsA than in RA. The upregulation of the cytokine receptors in PsA r econfirms its inflammatory nature, but indicates the more benign cours e of disease compared with RA.