PRTN3 and rheumatoid arthritis: P. gingivalis has been hypothesized to play a causative role in RA by inducing the production of antibodies to citrullinated proteins (ACPA) (10), and, recently, the ability of C-terminal citrullinated peptides generated by concerted action of Arg-specific gingipains and PPAD to breach immunotolerance was implicated as a causal link (11).