In particular, compared with control mice, leptin-deficient mice presented a less severe antigen-induced arthritis, decreased levels of TNF-α and IL-1β in knees synovium, and an impaired antigen-specific T cell proliferative response with lower IFN-γ and higher IL-10 production, which indicates a shift toward Th2 cell response (Busso et al., 2002). This evidence concerns the gene LEP and arthritic joint disease.