TNF and psoriasis: Our results showed a significant attenuation of psoriasis symptoms (erythema, scaling, and skin thickness) in mice treated with intact hUCB-MSCs, hUCB-MSCs preconditioned with IL-22 and TNF-α, and hUCB-MSC-Exo preconditioned with IL-17, IL-22 and TNF-α (MSC-Exo 3C).