Administration of IL-33 increases TNF-α production, increases the number of effector T cells in the lamina propria, and increases GVHD severity; administration of soluble ST2 (the IL-33 receptor) to block IL-33 binding to membrane-bound ST2 on donor T cells reduces inflammatory cytokines, attenuates GVHD damage to the GI tract, and improves overall survival. Here, TNF is linked to graft versus host disease.