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. Here, PRTN3 is linked to rheumatoid arthritis.