Aging reduced the pathogenicity of Th17 cells and ameliorated experimental autoimmune uveitis in mice as shown in this blue disc. In young mice with experimental autoimmune uveitis, Th17 cells with strong pathogenicity led to severe vasculitis (inflammation of the blood vessels), diffuse chorioretinal lesions, and massive inflammatory exudation in the fundus. On the contrary, in old mice with experimental autoimmune uveitis, Th17 cells with weakened pathogenicity only led to small and focal chorioretinal lesions, minimal vasculitis, and mild inflammatory exudation.