In preclinical studies involving mouse models of dextran sulfate sodium (DSC)-induced ulcerative colitis (UC) and imiquimod (IMQ)-induced psoriasis, the researchers demonstrated that mesenchymal stem cell-derived small extracellular vesicles (MSC-sEVs) expressing PD-L1 effectively inhibited inflammatory immune cells, targeting and repairing tissue damage through the PD-1/PD-L1 pathway. The gene discussed is CD274; the disease is ulcerative colitis.