Patients who have not had adequate blood count recovery post related or unrelated stem cell transplant will be given a "boost" of T-cell depleted, enriched stem cells to hopefully improve their blood counts.

Patients who have not had adequate blood count recovery post related or unrelated stem cell transplant will be given a "boost" of T-cell depleted, enriched stem cells to hopefully improve their blood counts.

The unrelated donors will receive G-CSF prior to pheresis (collection of the stem cells) to boost the number of CD34+ cells. The related donors will receive G-CSF and AMD3100 prior to pheresis to boost the number of CD34+ cells. Once the CD34+ cells are collected they will be T-cell depleted using a cell separation device called the CliniMACS systems. The CliniMACS system will select the CD34+ cell and remove the T-cells. By removing the T-cells we can minimize the risk of Graft Versus Host Disease (GVHD). The enriched CD34+ cells will be given to them to hopefully give them a "boost" of cells that can permanently produce new blood cells to improve their risk of infection and bleeding.

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.