This led to arthritis in respectively 60% and 95% of WT and S100a8-/- mice (Fig 4C), the latter developing more severe disease, with a mean score of 8.3 ± 1.1 on day 35, compared to 5.7 ± 1.3 for WT (Fig 4D). The gene discussed is S100A8; the disease is arthritic joint disease.