CD226 and Arthritis: Clinical evidence of arthritis (defined by at least one joint with a score > 1) was observed in 5/7 (71%) mice treated with anti-DNAM-1 mAb, 6/7 (86%) mice treated with control IgG and 7/7 (100%) mice injected with PBS (p = 0.51 and 0.13) (Figure 1a).