SOLUBLE INTERLEUKIN-6 (IL-6) RECEPTOR AND IL-6 LEVELS IN SERUM AND SYNOVIAL-FLUID OF PATIENTS WITH DIFFERENT ARTHROPATHIES

Objective. We studied interleukin 6 (IL-6) and soluble IL-6 receptor ( sIL-6R) in serum and synovial fluid (SF) to investigate their role in different arthropathies, Methods. IL-6 was measured by ELISA and bioas say and sIL-6R by ELISA, in 210 sera and 73 SF samples from 49 patient s with rheumatoid arthritis (RA), 20 crystal deposition disease, 17 os teoarthritis (OA), 24 with other inflammatory arthropathies, and 100 c ontrols, In all patients, disease activity was assessed by erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP); in patients wi th RA and other arthropathies pain, tender and swollen joints, and Rit chie index were also evaluated. Total leukocyte count in SF was determ ined. Results, There was good correlation between IL-6 ELISA and bioas say levels both in serum (r = 0.62, p = 0.0001) and in SF (r = 0.72, p = 0.0001), Serum IL-6 was detected only in patients with inflammatory arthritis and SF IL-6 was detected in all patient groups. Serum IL-6 correlated with swollen joints (r = 0.35, p = 0.05), ESR (r = 0.46, p = 0.001), and CRP (r = 0.46, p = 0.001) in RA; and with CRP (r = 0.89, p = 0.0001) in crystal deposition disease, SF IL-6 correlated with ES R (r = 0.54, p = 0.007) and CRP (r = 0.42, p = 0.04) in RA; with SF to tal leukocyte count (r = 0.61, p 0.004) in crystal deposition disease; and with SF total leukocyte count (r = 0.61, p = 0.009) in OA, No cor relations were found in the group with other inflammatory diseases, No correlations were found between sIL-6R and lL-6 or between sIL-6R and disease activity variables in any group of patients, Conclusion. Unli ke IL-6, sIL-6R is not produced at the site of inflammation and is not related to clinical or biological disease activity variables, Only in RA are both IL-6 and sIL-6R levels increased, suggesting that sIL-6R may reinforce the systemic effect-a of IL-6.