To test the possibility that the lack of protection we observed in the IL-2 accelerated GVHD model was due to insufficient number of TRegs and not due to dysfunction of the in vivo expanded cells, we first tested protection from GVHD induced by transfer of 1×106 PBMCs in animals reconstituted with 5×106 TRegs 10 days earlier. This evidence concerns the gene IL2 and graft versus host disease.