T-Lymphocytes Genetically Targeted to the B-Cell Specific Antigen CD19 in Pediatric and Young Adult Patients With Relapsed B-Cell Acute Lymphoblastic Leukemia

The purpose of this study is to test the safety of giving the patient special cells made from their own blood called "Modified T-cells". The goal is to find a safe dose of modified T-cells for patients whose leukemia has returned to the bone marrow.

Inclusion Criteria for Collection Arm of the protocol: Age \< 26 years, whose disease meets one of the following 3 criteria: * VHR\* * Patients in 1st or subsequent marrow relapse (isolated or combined), at the time of relapse, during retrieval therapy, or after achievement of CR. * Refractory disease \*Definitions of VHR B-ALL include the following: * NCI HR-ALL and age ≥ 13 years at diagnosis * CNS-3 leukemia at diagnosis * Day 29/End of Induction BM MRD \> 0.01% * Induction failure (M3 BM at Day 29/End of Induction) * Hypodiploidy (n\< 44 chromosomes and/or a DNA index \< 0.81) * t(9;22) ALL (Philadelphia Chromosome/Ph+ ALL) * t(17;19) ALL or Ph-Like ALL * MLL gene rearrangement * IKZF1 deletions * Intrachromosomal amplification of chromosome 21 (iAMP21) Please note patients that only meet the criteria for collection/storage of PBMCs will need to be reconsented prior to infusion of genetically modified T-cells. Inclusion Criteria for Treatment Arm of this protocol: * Patients must have a history of relapsed/refractory CD19+ B-ALL involving the marrow to be eligible for infusion of modified T cells. * Please note ≥5% blasts by morphology, FISH/cytogenetics, molecular translocation and/or flow cytometry constitutes a bone marrow relapse on this protocol. Patients must also fulfill one of the following criteria to be eligible for infusion of modified T cells: * Second or greater (≥2) relapse * Early first marrow relapse (1st CR \18 months) with poor initial response (≥5% blasts by morphology and/or flow cytometry) following reinduction chemotherapy * Refractory Disease * Ineligible for HSCT as determined by the treating physician in consultation with the BMT service * Patient would not benefit from additional chemotherapy as determined by the treating physician * KPS or Lansky score ≥ 60 * Pulmonary function (measured prior to conditioning chemotherapy): o \> 90% oxygen saturation on room air by pulse oximetry. * Renal Function (measured prior to conditioning chemotherapy): o Serum creatinine ≤2.0mg/dL for patients over 18 years or ≤2.5 x institutional ULN for age * Hepatic Function (measured prior to conditioning chemotherapy): * AST ≤ 5 x the institutional ULN. Elevation secondary to leukemic involvement is not an exclusion criterion. Leukemic involvement will be determined by the presence of progressive relapse defined by escalating bone marrow or peripheral blood leukemia blasts within the previous month and the absence of initiation of know hepatotoxic medication (e.g. azoles). * Total bilirubin ≤ 2.5 x the institutional ULN Exclusion Criteria for Collection of T cells/PBMCs: * Karnofsky/Lansky performance status \