Figure 1

Histopathological patterns and 78-kDa glucose-regulated protein (GRP78) staining of rheumatoid synovium. The typical synovium with diffuse synovitis is shown in (a). Synovium presented diffuse lymphocyte infiltration without specific microanatomical organization. The representative rheumatoid synovium with follicular synovitis is shown in (b). The lymphoid aggregates are extensive and assume the appearance of discrete lymphoid follicles with germinal center formation. The reactive germinal center, characterized by pale-staining centroblasts with deeply stained mantle zones, is shown in (c). Representative immunohistochemical stainings for the sequential sections of follicular synovitis (d-f), diffuse synovitis (g-i), and osteoarthritis (OA) synovium (j-l) are presented. Frames (d), (g), and (j) show hematoxylin and eosin stainings. In follicular synovitis, GRP78 stainings for plasma cells surrounding lymphoid follicles are clear and intensive in contrast to no or only weak stainings for small lymphocytes and large centroblasts within lymphoid follicles (e) and moderate GRP78 stainings for infiltrating plasma cells in diffuse synovitis (h). There are no or only weak GRP78 stainings for plasma cells (arrows) in OA synovium (k). The normal goat serum IgG replaces the primary antibody as a negative control (f, i, and l). Representative double-immunofluorescent stainings in synovium from rheumatoid arthritis (RA) and OA patients are shown in (m-u). Frames (m), (p), and (s) show the expression of CD138 (bright red fluorescent light), and frames (n), (q), and (t) show the expression of GRP78 (bright green fluorescent light) in synovium with follicular synovitis, diffuse synovitis, and OA, respectively. Frames (o), (r), and (u) (merged) reveal the coexpression of CD138 and GRP78. The bar graph shows that there is a statistical difference in the expression of GRP78 of infiltrating plasma cells between RA (follicular synovitis + diffuse synovitis) and OA synovium (**P < 0.001) as well as between follicular and diffuse synovitis (*P < 0.001). Original magnifications: ×400 (a-c), ×1,000 (d-l), and ×800 (m-u). DS, diffuse synovitis; FS, follicular synovitis.