 Most GVHD-related deaths are either the direct consequence of severe GVHD or from infections associated with intense immunosuppression, a consequence of the standard treatments for acute GVHD, which almost always include high-dose steroids. A more effective prophylaxis therapy that allows for the GVL effect to develop, while limiting the exposure to high-dose steroids may reduce transplant mortality and morbidity. We also will study how key chemical and cellular factors relate to clinical outcome. 