GRAFT-VERSUS-HOST DISEASE PROPHYLAXIS: Patients receive rituximab intravenously (IV) on days -6, 1, 8, and 15 and anti-thymocyte globulin IV over 6-8 hours on days -3 to -1. Patients also receive tacrolimus IV continuously and then orally (PO) beginning on day -1 and continuing until day 150 followed by a taper until day 180 and mycophenolate mofetil PO or IV twice daily on days -1 to 60.