PRTN3 and rheumatoid arthritis: Specifically, RA patients with positive anti-citrullinated protein antigen (ACPA) antibodies exhibit a higher abundance of P. gingivalis in their oral microbiota, and P. gingi-valis expresses peptidylarginine deiminiase (PAD), which can convert arginine to citrulline in host proteins, generating citrullinated antigens.[29] Aggregatibacter actinomycetemcomitans,[30] which is also linked to periodontitis, is another oral bacterial microbe which shares the ability to generate citrullinated autoantigens.