CXCL8 and rheumatoid arthritis: Baseline average levels of the cytokines were as follows: IL-8 in RA 40.16 ± 21 pg/ml and in OA 44 ± 35 pg/ml; IL-6 in RA 363.9 ± 221 pg/ml and in OA 308.6 ± 251 pg/ml; MMP-3 in RA 0.25 ± 0.13 ng/ml and in OA 0.34 ± 0.12; pro-MMP1 in RA 0.44 ± 0.2 ng/ml and in OA 0.40 ± 0.28 ng/ml (mean ± SD).