Cord Blood Stem Cell TransplantationTransplantation, HomologousHematopoietic Stem Cell TransplantationGraft vs Host DiseaseTransplantation ConditioningFetal BloodHematologic NeoplasmsGraft vs Leukemia EffectGraft vs Tumor EffectLeukemiaTransplantation, AutologousBone Marrow TransplantationSpinal CordTreatment OutcomeRetrospective StudiesRecurrenceAcute DiseaseSpinal Cord InjuriesTime FactorsTransplantation ChimeraSurvival RateIsoantigensT-LymphocytesGraft SurvivalLymphocyte Culture Test, MixedHistocompatibility TestingTissue DonorsUmbilical CordFollow-Up StudiesStem Cell TransplantationBlood BanksHistocompatibilityWhole-Body IrradiationAntigens, CD34Risk FactorsTransplantation, IsogeneicProspective StudiesInfant, NewbornHematopoietic Stem CellsBusulfanLymphocyte ActivationMyeloablative AgonistsSkin TransplantationTransplantation ImmunologyGraft vs Host Reaction