In RA patients' synovial sites, citrullinated RA-related
antigens such as type II
collagens,
fibrin (
ogen),
vimentin, and α-
enolase could be targeted by ACCPAs. Since ACCPA production can be initiated a long time before RA sign appearance, primary auto-immunization against these citrullinated
proteins can be originated from extra-articular sites. It has been shown that there is a significant association between P. gingivalis
periodontitis, anti- P. gingivalis
antibodies, and RA. P. gingivalis
gingipains (Rgp, Kgp) can degrade
proteins such as
fibrin and α-
enolase into some
peptides in the form of Arg in the C-terminal which is converted to
citrulline by PPAD. Also, PPAD can citrullinate
type II collagen and vimentins (SA
antigen). P. gingivalis induces
inflammation and chemoattraction of immune cells such as neutrophils and macrophages through the increase of C5a (
gingipain C5 convertase-like activity) and SCFA secretion. Besides, this microorganism stimulates anoikis, a special type of apoptosis, and NETosis, an antimicrobial form of neutrophil death, leading to the release of PAD1-4, α-
enolase, and
vimentin from apoptotic cells into the periodontal site. In addition,
gingipains can degrade macrophages CD14 and decrease their ability in apoptotic cell removal.
Gingipains also can cleave IgGs in the Fc region and transform them into
rheumatoid factor (RF)
antigens. In the present study, the effects of P. gingivalis on
rheumatoid arthritis autoimmune response have been reviewed, which could attract practical insight both in bench and clinic.