PRTN3 and periodontitis: Our data on anti-Rgp IgG in relation to ACPA and dsDNA antibodies on the other hand provide a strong rationale for further studies addressing the role of Rgp IgG as a biomarker for periodontitis patients at increased risk of developing specific autoimmunity linked to RA and SLE, as well as experimental studies exploring the molecular mechanisms underpinning these associations.