Our aim was to compare the therapeutic effects of human umbilical cord blood-derived MSCs (hUCB-MSCs) and their exosomes (hUCB-MSC-Exo), preconditioned with different combinations of proinflammatory cytokines IL-17, IL-22, and TNF-a, whose levels are elevated in psoriasis, using an in vivo imiquimod (IMQ)-induced psoriasis-like skin inflammation model in mice. The gene discussed is IL17A; the disease is psoriasis.