In this study, we demonstrated that intraperitoneal infection with a periodontitis-associated bacterium, A. actinomycetemcomitans, exacerbates arthritis in CAIA model by inducing cell infiltration into the inflamed synovium and diminution of bone volume by stimulating caspase-11-mediated IL-1β secretion from phagocytic cells. The gene discussed is IL1B; the disease is periodontitis.