Previous studies in mice have shown that the administration of an aqueous α‐GC stimulated host‐type iNKT cells and ameliorated acute GVHD by expanding donor Tregs via production of IL‐4.9, 10 Subsequently, a liposomal α‐GC (lipo α‐GC) was developed and reported to be tolerogenic and safe in vivo11; furthermore, its acute GVHD‐preventing effect was proven in a murine model.12 Here, IL4 is linked to graft versus host disease.