Rheumatoid arthritis (RA) is characterized by the accumulation of CD4+ memory T cells in the inflamed synovium. To address the mechanism, we analyzed chemokine receptor expression and found that the frequency of CXC chemokine receptor (CXCR)4 expressing synovial tissue CD4+ memory T cells was significantly elevated. CXCR4 expression could be enhanced by IL-15, whereas stromal cell-derived factor (SDF)-1, the ligand of CXCR4, was expressed in the RA synovium and could be increased by CD40 stimulation. SDF-1 stimulated migration of rheumatoid synovial T cells and also inhibited activation-induced apoptosis of T cells. These results indicate that SDF-1-CXCR4 interactions play important roles in CD4+ memory T cell accumulation in the RA synovium, and emphasize the role of stromal cells in regulating rheumatoid inflammation.

A unique feature in inflammatory tissue of rheumatoid arthritis (RA) is the formation of ectopic lymphoid aggregates with germinal center (GC)-like structures that can be considered to contribute to the pathogenesis of RA, because local production of the autoantibody, rheumatoid factor, is thought to be a causative factor in tissue damage. However, the factors governing the formation of GC in RA are presently unknown. To begin to address this, the expression of B cell attracting chemokine (BCA-1) (CXCL13), a potent chemoattractant of B cells, was examined in the synovium of patients with RA or with osteoarthritis (OA). Expression of BCA-1 mRNA was detected in all RA samples, but in only one of five OA samples. Lymphoid follicles were observed in four of seven RA samples and in two of eight OA samples, and in most of them BCA-1 protein was detected in GC. BCA-1 was not detected in tissues lacking lymphoid follicles. Notably, BCA-1 was detected predominantly in follicular dendritic cells in GC. CD20-positive B cells were aggregated in regions of BCA-1 expression, but not T cells or macrophages. These data suggest that BCA-1 produced by follicular dendritic cells may attract B cells and contribute to the formation of GC-like structures in chronic arthritis.

Rheumatoid arthritis (RA) is characterized by proliferation of synoviocytes that produce inflammatory cytokines and chemokines. The expressed chemokines are thought to be involved in the migration of inflammatory cells into the synovium. In this study we show that CCL2/monocyte chemotactic protein-1, CCL5/RANTES, and CXCL12/stromal cell-derived factor-1 enhanced IL-6 and IL-8 production by fibroblast-like synoviocytes (FLS) from patients with RA, and their corresponding receptors, CCR2, CCR5, and CXCR4, respectively, were expressed by RA FLS. The chemokines stimulated RA FLS more effectively than skin fibroblasts. Culture with CCL2 enhanced phosphorylation of extracellular signal-related kinase 1 (ERK1) and ERK2, but not phosphorylation of p38 or Src. Moreover, activation of ERK1/2 was inhibited by pertussis toxin, a Gi-coupled protein inhibitor, and RS-504393, CCR2 antagonist, suggesting that ERK1/2 was activated by CCL2 via CCR2 and Gi-coupled protein. On the other hand, CCL2, CCL5, and CXCL12 were expressed on RA FLS, and their production was regulated by TNF-α, IL-1β, and TGF-β1. Our results indicate that the chemokines not only play a role in inflammatory cell migration, but are also involved in the activation of FLS in RA synovium, possibly in an autocrine or paracrine manner.

Objective. Rheumatoid arthritis (RA) is a chronic inflammatory disease associated with massive T cell infiltration into the synovium. The accumulated T cells express type 1 cytokines, such as interferon-␥ (IFN␥) and tumor necrosis factor ␣, and activated markers of inflammation, such as CD154 and inducible costimulator (ICOS). It is thought that chemokines contribute to T cell accumulation in the synovium. In this study, we examined the role of CXCL16 and CXCR6 in T cell migration and stimulation in RA synovium.Methods. Expression of CXCL16 and CXCR6 was analyzed by immunohistochemistry, reverse transcription-polymerase chain reaction, Western blotting, and/or flow cytometry. Migration activity was assessed using a chemotaxis chamber. IFN␥ production was analyzed by enzyme-linked immunosorbent assay. The effect of anti-CXCL16 monoclonal antibody on murine collagen-induced arthritis (CIA) was evaluated.Results. CXCL16 was expressed in RA synovium.