In a first experimental group, male and female Mmp8+/+ (n = 10), Mmp8+/- (n = 10) and Mmp8-/- (n = 10) mice were injected intraperitoneally at day 0 and 2 with 200 μl K/BxN mice serum and monitored for signs of arthritis. The gene discussed is MMP8; the disease is arthritic joint disease.