Granulocyte Colony-stimulating Factor (G-CSF) Plus or Minus AMD3100 for Engraftment Post Allogeneic Transplant

Inclusion Criteria: Recipient * Must be age ≥ 18 * Must have ≥90 % donor cells in the unfractionated peripheral blood based on either XY FISH or standard STR. * More than 60 days post allogeneic stem cell transplantation. * Must meet one of the following criteria: * platelets \< 20,000 or * ANC\<500 or * transfusion dependent for at least one cell line and /or * on growth factor support (G-CSF) without adequate response for 30 days and * no reversible etiology found after an allogeneic stem cell transplantation * Patient has an ECOG performance status of 0-2. * The original stem cell donor must be available, willing, and medically able to undergo Mobilization and a maximum of 2 apheresis procedures * Each patient (recipient) or legal guardian and donor must be willing to participate as a research subject and must sign an informed consent form. Unrelated Donors * NMDP guidelines for eligibility will be followed using G-CSF alone mobilization. Related donors * Must be ≥18 yrs old and ≤ 75 years old. * Donor must be sero-negative for HIV-1\&2 antibody and HTLV-I\&II antibody, by FDA licensed test. * Donor must have adequate renal function as defined by serum creatinine ≤ 1.5X institution ULN and AST and ALT ≤ 3X ULN and total bilirubin less than 2 mg/dl. * Donor must be agreeable to mobilization and the second donation of PBMC. * Women of child bearing potential should be willing to avoid becoming pregnant while receiving treatment with plerixafor. * Donor must have adequate peripheral venous catheter access for leukapheresis or must agree to placement of a central catheter. Exclusion Criteria: Recipient * Patients with confirmed relapse of their original disease * Participation in other clinical trials that involve investigational drugs or devices except with permission from the Principal Investigator and Sponsor. * Patients with documented active viral, bacterial or fungal infections. * Documented allergy to murine proteins or iron dextran. * Pregnancy * Patients with immune mediated graft dysfunction. Donor * Evidence of active infection at the time of study entry. * Medical or physical reason which makes the donor unlikely to tolerate or cooperate with growth factor therapy and leukapheresis * Factors which place the donor at increased risk for complications from leukapheresis or G-CSF therapy(e.g., autoimmune disease, multiple sclerosis, sickle cell trait, coronary artery disease). * Pregnancy (positive serum or urine beta-HCG) or breastfeeding. Women of childbearing age must avoid becoming pregnant while on the study.