Figure 4.

Role of MPs in RA. The high concentrations of MPs from different leukocyte populations reported in the synovial fluid from RA patients must be citrullinated and form ICs with anti-CCP antibodies and RF autoantibodies. These complex structures could be recognized by Mo/MΦ through isotype-specific Fc receptors (FcγR and FcμR) and induce the production of proinflammatory cytokines such as TNF-alpha, IL-6, and the chemokines CCL2, CCL3, and RANTES. These soluble factors participate in the systemic inflammation in the synovium and the destructive changes observed in the joints of RA patients. IL-6 is also involved in the induction of plasma cells (PCs) producing autoantibodies.