Functional implications of B lymphocytes in the development of rheumatoid arthritis

B cells play a key role in regulating the immune system by producingantibodies, acting as antigen-presenting cells, providing support toother mononuclear cells, and contributing directly to inflammatorypathways. Accumulating evidence indicates that there is a disruptionof these regulated processes in the pathogenesis of autoimmunediseases, including rheumatoid arthritis (RA). In RA there is a chronic inflammation in the affected joints leading to the development of ectopic germinal centers. A micro-environment is established which supports B cell activation and differentiation. Plasma cells may develop which secrete autoantibodies of high affinity directly into the synovial tissue. As a result, antigen/antibody complex formation, the activation of the complement cascade and the stimulation of macrophages may contribute to the destruction of joints. B cells also play a pivotal role in the activation of synovial T cells and the induction of cytokine secretion. Finally, the success of B cell depletion therapy by using monoclonal antibodies against CD20 further emphasized the importance of B cells in the pathogenesis of RA