The expression of CRP in serum, synovial fluid (SF), and synovial tissues of RA patients. (A) SF and serum of 20 RA patients were collected and CRP level was measured using an immunoturbidimetric method. There is significant correlation between SF and serum levels of CRP (R2 = 0.58, P <0.05). (B) SF IL-6 and IL-6 levels were measured using sandwich ELISA. SF CRP level is correlated with SF IL-6 level (R2 = 0.62, P <0.05). (C) There is no correlation between SF CRP and SF RANKL levels in RA patients. (D) Immunohistochemical staining for CRP in the synovium of patients with RA and osteoarthritis (OA) shows abundant expression of CRP in the synovial lining and sublining areas in RA synovium, while there is minimal expression of CRP in OA synovium (original magnification: 200× and 400×). The figures are representatives of three independent experiments. (E) The quantitative measurement of positive area using ImageJ is larger in RA synovium than OA synovium (original magnification; 400×). **
P <0.01. CRP, C-reactive protein; ELISA, enzyme-linked immunosorbent assay; IL, interleukin; RA, rheumatoid arthritis; RANKL, receptor activator of nuclear factor kappa-B ligand.