• Incidence of non-engraftment and graft rejection, Incidence of grade II-IV and grade III-IV acute GvHD 100d, Incidence of extensive and limited chronic GvHD from 100d to 365d, and Incidence of regimen-related morbidity and mortality 100d [ Time Frame: Day100 and Day 365 ] [ Designated as safety issue: Yes ]
  

• Days to absolute neutrophil count (ANC) of 500/mm3, Days to achieve a platelet count of 20,000 and 50,000/mm3 w/o transfusions Day to last red cell transfusion Survival at 1 year will also be estimated [ Time Frame: 1 year ] [ Designated as safety issue: Yes ]
  

Drug: Campath-1H
Day-8 through Day-6 dosing per institutional SOP
Drug: anti-CD45
Day-5 through Day-2 400ug/kg over 6 hr
Drug: Fludarabine
Day-8 through Day-4 30 mg/m2

Before treatment begins, patients will be evaluated to confirm that they meet the requirements of this study. Participants will need to have a central line. This is a thin plastic catheter or tube that is placed during surgery into one of the large veins in the chest or neck. Central lines are used to give intravenous (IV) medications (medicines that go directly into the vein) or to take blood samples without you having to endure frequent needle sticks.

CAMPATH-1H will be given as a daily 4-hour IV (intravenous, by vein) infusion for three days. Anti-CD45 will be given as a daily 6-hour IV infusion over the next 4 days. There will then be a one-day rest period before receiving the stem cell transplant.

After the transplant, participants will be followed closely. While in hospital, patients will have a physical examination done daily. They will also have a daily urinalysis (where some of your urine is tested to see what it contains) and blood tests done, which are standard for anyone receiving a transplant.

To see how the Anti-CD45 is working in the body, blood will be drawn 2 hours before each infusion of the Anti-CD45, at the end of each infusion of the CD45 and then 24 hours (1 day) and 48 hours (2 days) after the end of the last infusion of Anti-CD45. No more than 42 mls (8-9 teaspoonfuls) of total blood will be drawn over the course of the four Anti-CD45 infusions.

When able to leave the hospital, the patient will be followed in the outpatient clinic and will have visits and tests which are standard (the same) for anyone who receives a transplant.