CDA and rheumatoid arthritis: The biological activity of the synovial aggregate structures is still undefined—contradictory data on their role in the promotion of autoimmunity, chronic inflammation and driving the production of pathogenetic autoantibodies exist: Humby et al demonstrated that synovial follicular units in RA express activation-induced cytidine deaminase and are surrounded by ACPA-producing plasma-cells3, whereas Cantaert et al demonstrated that ectopic lymphoid neogenesis is not directly associated with the local production of ACPA and RF in RA joints29.