IL4 and graft versus host disease: Based on our previous studies, the helminthic regulation of GVHD is dependent on Th2 cytokine IL4 generation by recipient cells, which in our further studies in IL4Rα-/-, T cell-specific IL4Rα-/- and STAT6-/- BMT recipients [6,10,11] appears to act on other BMT recipient cells (more specifically on recipient cell IL4 receptor and STAT6) to condition the host and regulate GVHD.