- De novo acute GVHD diagnosed within 48 hours prior to enrollment; biopsy confirmation of GVHD is strongly recommended but not required; enrollment should not be delayed awaiting biopsy or pathology results; the patient must have had no previous systemic immune suppressive therapy given for treatment of acute GVHD except for a maximum 48 hours of prior corticosteroid therapy (at least 1 mg/kg/day methylprednisolone)