B cells in rheumatoid arthritis

Normally the immune response is restricted to the peripheral secondary lymphoid organs. However, additional ectopic lymphoid tissue may develop at chronic sites of inflammation. In the synovium of rheumatoid arthritis patients the local production of proinflammatory cytokines seems to support the formation of a precisely structured microenvironment, which allows an antigen dependent immune response to take place. The analysis of the V-gene repertoire expressed in synovial B cells demonstrated that in the inflamed synovium a germinal centre reaction takes place. Antigen presented by a network of follicular dendritic cells may activate synovial B cells and support their differentiation into plasma cells secreting high affinity antibodies. The specificity of these antibodies remains to be determined.