Patients will be pre-medicated with Diphenhydramine 1mg/kg IV (max 50 mg) and Acetaminophen 10mg/kg po (max 650 mg). 800ug/kg CD45 Mabs will be given as 2 daily intravenous infusions over 8 hours. The antibody aliquot to be infused will arrive in the treatment area hand-carried by the attending physician or appointed designate. The antibody aliquot will be diluted in minimal amounts of normal saline. The resulting solution is stable for 24 hours. The antibody solution is administered by a syringe pump in incremental doses, 0.2-0.8 mg in the first hour and up to 10 mg/hr thereafter, for a total infusion time of a maximum of 6 hrs. A registered nurse and a physician must be readily available.