The distribution of Fn and citrullinated proteins in arthritic synovial tissues from RA and OA patients. (A) Immunohistochemistry staining. Continuous sections of RA or OA synovial tissues were probed with ant-Fn Ab and anti-MC Ab, respectively. For negative controls, primary Ab was replaced by normal serum. Original magnification: x200. (B) Double immunofluorescent staining. The sections of RA or OA synovial tissues were probed with anti-Fn Ab and anti-MC Ab, followed by incubation with second antibody anti-rabbit IgG FITC (green) or anti-mouse IgG PE (red). Original magnification: x200. anti-MC Ab, criteria anticitrulline (modified) antibody; FITC, fluorescein isothiocyanate; Fn, fibronectin; IgG, immunoglobulin G; OA, osteoarthritis; RA, rheumatoid arthritis.