PRTN3 and rheumatoid arthritis: A particular role for Porphyromonas gingivalis (Pg) and Aggregatibacter actinomycetemcomitans (Aa) has been suggested in periodontitis and rheumatoid arthritis (RA), as these bacteria could initiate the formation of rheumatoid factor (RF) and anticitrullinated protein autoantibodies (ACPA).