Incidence of LPD in patients receiving CD6⁺CD8⁺ T cell–depleted marrow with or without EBV CTL prophylaxis. Kaplan-Meier analysis was based on 90 patients who received CTLs prophylactically compared with 42 who were enrolled on the same transplantation protocol but who did not receive CTLs. These patients were treated on Institutional Review Board-approved transplantation protocols open to patients with hematologic malignancies at St Jude Children's Research Hospital (1993-2000) or Baylor College of Medicine (1998-2000) where they received marrow from a matched unrelated donor or mismatched family member that had been depleted of T cells with antibodies to CD6 and CD8 after conditioning with cyclophosphamide, cytarabine, total body irradiation, and antithymocyte globulin.¹¹  All recipients received cyclosporine A at a dosage adjusted to attain plasma concentrations of 250 to 350 ng/mL. The control patients were enrolled on the same study but had either declined enrollment on the CTL prophylaxis study or were not eligible. The difference in incidence rates is highly significant.