Human cartilage gp-39+, CD16+monocytes in peripheral blood and synovium : correlation with joint destruction in rheumatoid arthritis

Objective. To investigate the expression of human cartilage (HC) gp-39, a possible autoantigen in rheumatoid arthritis (RA), in peripheral brood and synovium, to characterize its cellular source, and to analyze correlations with clinical features, Methods. The expression of HC gp-39 in synovium and peripheral blood mononuclear cells (PBMC) was assessed by immunohistochemistry and flow cytometry, Synthesis and secretion were investigated by both reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. Results. PBRIC expressing HC gp-39 were increased in RA patients compared with spondylarthropathy patients (P = 0.0029) and with healthy control subjects (P = 0.0013), HC gp-39+ cells were also slightly overrepresented in RA synovium (P = 0.01). In both blood and synovium, HC gp-39+ cells were identified as CDT4dim, CD16+ monocytes, a phenotype which can differentiate from classic CD14++ monocytes by maturation in vitro. HC gp-39 messenger RNA was detected in RA synovium and PBMC, and PBMC secreted HC gp-39 in vitro. The number of HC gp-39+ PBMC correlated with serum levels of C-reactive protein (r = 0.39, P = 0.003) and HC gp-39 (r = 0.52, P = 0.014). HC gp-39 expression in Ri synovial lining correlated with joint destruction (r = 0.77, P < 0.001), Conclusion, CD16+ monocytes, a cellular source of HC gp-39 in vivo, are overrepresented in both RA peripheral blood and synovial tissue. The presence of HC gp-39+ cells in RA synovium is correlated with the degree of joint destruction. These data support a role of these cells in the local autoimmune response that leads to chronic inflammation and joint destruction