AhR deficiency blocks cartilage destruction and reduces matrix metalloproteinase-3 levels and ameliorated collagen II-induced arthritis (CIA), a mouse model of rheumatoid arthritis (RA), while demonstrating that the pro-inflammatory effects of AhR in mice with collagen-induced arthritis can be mediated by Th17 cells and IL-22. The gene discussed is AHR; the disease is Arthritis.