IL17A and Erythema: Furthermore, we confirmed that IFNγ-sEVs reduced psoriasis symptoms including thickness, erythema, and scales of skin lesions; exhausted Th17 cells, increased Th2 cells; and reduced enrichment of inflammatory cytokines such as IL-17A, IFN-γ, IL-6, and TNF-α in both spleen and skin lesions in vivo.