This project will support a clinical trial utilizing monoclonal antibodies to remove immunocompetent T cells from donor marrow prior to infusion into the recipient in an effort to eliminate or reduce the occurance of graft versus host disease. Monoclonal antibodies will also be used post-transplant, as necessary, to treat graft versus host disease. The result from this study will provide more comprehensive insight into designing efficacious treatment modalities for bone marrow transplant.