PRTN3 and rheumatoid arthritis: Since the presence of anti-Rgp antibodies reflects Pg infection, the data could implicate that Pg infection triggers ACPA-production, as proposed by Rosenstein et al.3 We know from our earlier retrospective study, that elevated anti-Rgp IgG levels are long-term stable during 10–12 years before RA diagnosis, while ACPA levels gradually increase during this time,9 suggesting that Pg infection may precede the ACPA-response.