Interleukin 22 (IL-22) expression is associated with increased joint destruction and disease progression in rheumatoid arthritis (RA). Although IL-22 is considered a pro-inflammatory cytokine, its mechanism of action in RA remains incompletely understood. Here, we used the collagen-induced arthritis model in IL-22 deficient (IL-22−/−) mice to study the role of IL-22 in RA. In spite of normal disease incidence, disease severity is significantly diminished in IL-22−/- mice.
