In a T1DM mouse model, hexyl 5-aminolevulinate (HAL)-loaded engineered cytokine-primed MSCs (H@TI-ev) exhibited high therapeutic efficacy by reducing CD4+ T cell density and activation through the PD-L1/PD-1 axis, and inducing macrophage transformation from M1 to M2 to remodel the immune microenvironment (85). The gene discussed is CD274; the disease is type 1 diabetes mellitus.