This concept was tested in very stringent immunological models: short-term Bcl-2/Bcl-xL inhibition was sufficient to substantially alleviate GVHD, to inhibit allogeneic immune responses against fully MHC-mismatched skin grafts and to allow bone marrow engraftment without myelosuppression in a mixed chimersm model. The gene discussed is BCL2; the disease is graft versus host disease.