Importantly, the GVHD score of the livers from CD19-CAR-IL-15 T-treated mice was approximately 4, whereas that of the livers from CD19-CAR-IL-15-IL-15Ra T-treated mice was approximately 0, demonstrating the inhibitory effect of IL-15Ra on the IL-15 toxicity. This evidence concerns the gene IL15 and graft versus host disease.