RATIONALE: Giving monoclonal antibodies, such anti-CD45 monoclonal antibody and alemtuzumab, and chemotherapy drugs, such as fludarabine, before a donor stem cell transplant helps stop the patient's immune system from rejecting the donor's stem cells. When the healthy stem cells from a donor are infused into the patient they may help the patient's bone marrow make stem cells, red blood cells, white blood cells, and platelets.

PURPOSE: This phase I trial is studying the side effects and how well giving anti-CD45 monoclonal antibody together with alemtuzumab and fludarabine followed by donor stem cell transplant works in treating patients with severe combined immunodeficiency disease or other primary immunodeficiency disorder.

OBJECTIVES:

• To investigate whether anti-CD45 monoclonal antibody, alemtuzumab, and fludarabine followed by allogeneic stem cell transplantation using CD34+ selected cells promotes donor stem cell engraftment sufficient to provide T-cell function and B-cell function and to establish donor hematopoiesis in pediatric patients with severe combined immunodeficiency disease or other primary immunodeficiency disorder.
• To investigate whether this treatment regimen can be given with minimal and acceptable short term toxicity.
• To investigate the incidence of grade III-IV acute graft-versus-host disease in patients treated with this regimen.
• To estimate the 1-year survival of patients treated with this regimen.

OUTLINE: Patients receive alemtuzumab IV on days -8 to -6, fludarabine IV on days -8 to -4, and anti-CD45 monoclonal antibody IV over 6 hours on days -5 to -2. Patients undergo allogeneic stem cell transplantation on day 0.

After completion of study treatment, patients are followed periodically.

DISEASE CHARACTERISTICS:

• Diagnosis of one of the following:

  • Severe combined immunodeficiency disease (SCID), including SCID characterized by gene-specific mutations as well as clinical SCID without a defined genetic cause

  • Other severe primary immunodeficiency disorder, including any of the following:

    • Undefined T-cell deficiency disorder
    • Wiskott-Aldrich syndrome
    • Other severe immunodeficiencies for which satisfactory conventional therapy does not exist

• HLA mismatched (up to one haplotype) related donor OR HLA matched or mismatched (up to one antigen) unrelated donor available

  • No HLA matched related donor available

PATIENT CHARACTERISTICS:

• Lansky performance status (PS) or Karnofsky PS 70-100%
• Life expectancy > 6 weeks
• Creatinine ≤ 3 times normal for age
• HIV negative
• Negative pregnancy test
• Fertile patients must use effective contraception
• No symptomatic cardiac disease
• No evidence of significant cardiac disease by echocardiogram (i.e., shortening fraction < 25%)
• No known allergy to rat serum products
• No severe infection that, on evaluation by the Principal Investigator, precludes ablative chemotherapy or successful transplantation
• No severe personality disorder or mental illness

PRIOR CONCURRENT THERAPY:

• Not specified