Rationale: Fludarabine, cyclophosphamide, anti-thymocyte globulin and low-dose total body irradiation (LD-TBI) may induce the engraftment cross the immunologic barrier in the setting of HLA-haploidentical allogeneic hematopoietic cell transplantation. In addition, depletion of CD3 cells may contribute to prevent developing severe acute graft versus host disease (GVHD) in haploidentical transplantation.

Purpose: Phase II trials to evaluate the efficacy of haploidentical stem cell transplantation with fixed dose of T cells after in vitro T cell depletion using CD3 monoclonal antibody for children with acquired severe aplastic anemia

Inclusion Criteria:

• Diagnosis of life-threatening marrow failure (severe aplastic anemia) of nonmalignant etiology meeting 2 of the following criteria:

  • Granulocyte count < 500/mm3,
  • Corrected reticulocyte count < 1%,
  • Platelet count < 20,000/mm3

• No HLA-identical family member or closely matched (8 of 8 HLA-locus match) unrelated marrow donor available

• HLA-haploidentical related donor available

Exclusion Criteria:

• Paroxysmal nocturnal hemoglobinuria or Fanconi anemia
• Clonal cytogenetic abnormalities or myelodysplastic syndromes
• Active fungal infections
• HIV positive
• Severe disease other than aplastic anemia that would severely limit the probability of survival during the graft procedure
• Pregnant or nursing