RT Journal Article SR Electronic T1 Antibodies to Porphyromonas gingivalis Are Associated with Anticitrullinated Protein Antibodies in Patients with Rheumatoid Arthritis and Their Relatives JF The Journal of Rheumatology JO J Rheumatol FD The Journal of Rheumatology SP 1105 OP 1112 DO 10.3899/jrheum.091323 VO 37 IS 6 A1 CAROL A. HITCHON A1 FATIHA CHANDAD A1 ELIZABETH D. FERUCCI A1 ANNEMIEK WILLEMZE A1 ANDREEA IOAN-FACSINAY A1 DIANE van der WOUDE A1 JANET MARKLAND A1 DAVID ROBINSON A1 BRENDA ELIAS A1 MARIANNA NEWKIRK A1 RENE M. TOES A1 TOM W.J. HUIZINGA A1 HANI S. EL-GABALAWY YR 2010 UL http://www.jrheum.org/content/37/6/1105.abstract AB Objective. Anticitrullinated protein antibodies (ACPA) are relatively specific for rheumatoid arthritis (RA), and predate disease. The oral pathogen Porphyromonas gingivalis may play a role in breaking immune tolerance to citrullinated antigens. We studied a cohort of patients with RA and their relatives looking for associations between anti-P. gingivalis antibodies and ACPA. Methods. Patients with RA (n = 82) and their relatives (n = 205) from a North American Native (NAN) population were studied, along with 47 NAN and 60 non-NAN controls. IgM and IgA rheumatoid factor (RF) were tested by nephelometry and ELISA. Second-generation anticyclic citrullinated peptide (anti-CCP2) isotypes and IgG anti-P. gingivalis lipopolysaccharides were tested by ELISA. HLA-DRB1 typing was performed by sequencing. Oral hygiene and smoking habits were assessed by questionnaires. Results. Autoantibody frequency in patients with RA and relatives: ACPA 91% vs 19%, respectively; IgM RF 82% vs 17%; IgA RF 48% vs 22%. Anti-P. gingivalis levels were higher in patients with RA compared to relatives and controls (p = 0.005) and higher in ACPA-positive patients with RA than in ACPA-negative patients with RA (p = 0.04) and relatives (p < 0.001), but comparable in RF-positive and RF-negative patients and relatives. Poor oral hygiene and smoking were prevalent, but with no clear association with autoantibodies. Relatives with 2 shared-epitope alleles were more likely to be ACPA-positive (OR 2.5, p = 0.02). Conclusion. In a genetically predisposed population of NAN patients with RA and their relatives, anti-P. gingivalis antibodies were associated with ACPA. These findings suggest that immune responses to P. gingivalis may be involved in breaking immune tolerance to citrullinated antigens.