Constitutively active STAT6 sustained the GVT response without causing severe acute GVHD, where transgenic T cells generated robust quantities of cytotoxic proteins important in GVT response, such as granzymes A and B, interferon-γ and Fas ligand, in addition to generating high quantities of Th2/regulatory cytokines. This evidence concerns the gene STAT6 and acute graft versus host disease.