IL17A and Erythema: We found a significant attenuation of psoriasis symptoms (erythema, scaling, and skin thickness) in mice treated with intact hUCB-MSCs, hUCB-MSCs preconditioned with interleukin 22 (IL-22) and tumor necrosis factor alpha (TNF-α), and hUCB-MSC-Exo preconditioned with IL-17, IL-22, and TNF-a (MSC-Exo 3C).