Fig. 4

Evolution of experimental arthritis following pre-immunization with gingipain domains. a Scoring of the articular index in rats immunized with type II collagen. The scores used were on a 0–4 scale, as described in the “Materials and methods” section [24]. Shown are representative views of the ankles as the severity of the arthritis progresses: 0, no swelling or erythema; 1, slight swelling and/or erythema; 2, low to moderate edema; 3, pronounced edema with limited joint usage; and 4, excess edema with joint rigidity. b Effects of pre-immunization with recombinant gingipain domains on the severity of collagen-induced arthritis (CIA). Thirty-six rats were divided into six groups and received subcutaneous injection of PBS, incomplete Freund’s adjuvant (IFA), emulsified heat-killed Porphyromonas gingivalis (Pg), and emulsified HD, CD, and H4 domains of RgpA every week for 28 days. CIA was then induced by intradermal injections of bovine type II collagen. The clinical severity of arthritis in each paw was quantified throughout the experimental period according to a graded scale from 0 to 4. The scores for all four paws were summed to generate a representative arthritis score. Results are presented as mean ± SEM. *p < 0.05; **p < 0.01