Inclusion Criteria:

- Patients must have advanced AML or high-risk MDS meeting one of the following
descriptions:

- AML beyond first remission (i.e., having relapsed at least one time after
achieving remission in response to a treatment regimen)

- AML representing primary refractory disease (i.e., having failed to achieve
remission at any time following one or more prior treatment regimens)

- AML evolved from MDS or myeloproliferative syndromes; or

- MDS expressed as refractory anemia with excess blasts (RAEB)

- Patients not in remission must have CD45-expressing leukemic blasts; patients in
remission do not require phenotyping and may have leukemia previously documented to
be CD45 negative (because in remission patients, virtually all antibody binding is to
non-malignant cells which make up >= 95% of nucleated cells in the marrow)

- Patients must be >= 50 years of age

- Patients should have a circulating blast count of less than 10,000/mm^3 (control with
hydroxyurea or similar agent is allowed)

- Patients must have an estimated creatinine clearance greater than 50/ml per minute

- Bilirubin < 2 times the upper limit of normal (ULN)

- Aspartate aminotransferase (AST) and alanine transaminase (ALT) < 2 times the upper
limit of normal

- Eastern Cooperative Oncology Group (ECOG) =< 2

- Patients must have an expected survival of > 60 days and must be free of active
infection

- Patients must have an human leukocyte antigen (HLA)-identical sibling donor or an
HLA-matched unrelated donor who meets standard Seattle Cancer Care Alliance (SCCA)
and/or National Marrow Donor Program (NMDP) or other donor center criteria for PBSC
or bone marrow donation, as follows:

- Sibling donor; a patient and sibling donor should be matched for HLA-A, B, C,
DRB1 and DQB1 by an intermediate resolution deoxyribonucleic acid (DNA)-based
method

- Unrelated donor; an unrelated donor and recipient should be typed by a high
resolution DNA-based method, and ideally matched for HLA-A, B, C, DRB1 and DQB1
alleles, or if there is only a single locus disparity mismatched for an HLA-DQB1
antigen or allele; an unrelated donor may also be mismatched for any single 1)
one HLA-A, B or C antigen or allele, or 2) HLA-DRB1 allele (with or without
matching for HLA-DQB1)

- DONOR: Donors must meet HLA matching criteria and standard SCCA and/or National
Marrow Donor Program (NMDP) or other donor center criteria for PBSC or bone marrow
donation

Exclusion Criteria:

- Circulating human anti-mouse antibody (HAMA)

- Prior radiation to maximally tolerated levels to any critical normal organ, or > 20
Gy prior radiation to large areas of the bone marrow (e.g., external radiation
therapy to whole pelvis)

- Patients may not have symptomatic coronary artery disease and may not be on cardiac
medications for anti-arrhythmic or inotropic effects

- Left ventricular ejection fraction < 35%

- Corrected diffusion lung capacity of carbon monoxide (DLCO) < 35% or receiving
supplemental continuous oxygen

- Liver abnormalities: fulminant liver failure, cirrhosis of the liver with evidence of
portal hypertension, alcoholic hepatitis, esophageal varices, hepatic encephalopathy,
uncorrectable hepatic synthetic dysfunction as evidenced by prolongation of the
prothrombin time, ascites related to portal hypertension, bacterial or fungal liver
abscess, biliary obstruction, chronic viral hepatitis, or symptomatic biliary disease

- Patients who are known to be seropositive for human immunodeficiency virus (HIV)

- Perceived inability to tolerate diagnostic or therapeutic procedures

- Active central nervous system (CNS) leukemia at time of treatment

- Women of childbearing potential who are pregnant (beta-human chorionic gonadotrophin
[HCG+]) or breast feeding

- Fertile men and women unwilling to use contraceptives during and for 12 months
post-transplant

- Inability to understand or give an informed consent