Based on our findings, we propose the following working hypothesis of arthritis pathogenesis with Pg inoculation (administration) in SKG mice: (1) continued Pg inoculation results in changes in the gut microbiota, (2) dysbiosis of gut microbiota induces inflammation in intestinal tissues, (3) increased CP in the intestine accelerates systemic ACPA production, (4) severe joint destruction, and (5) CP generation via PgPAD. This evidence concerns the gene PRTN3 and arthritic joint disease.