The initial ATIMP dose administered is dependent upon B-ALL disease burden in the bone marrow. For patients with <20% marrow infiltration by B-ALL at baseline (screening), Dose 1a will be 1x108 CD19CAR T-cells and will be administered on Day 0 following LD. For those with ≥20% marrow infiltration by B-ALL, Dose 1b, administered on Day 0, will be 1x107 CD19CAR T-cells. This measure to prevent toxicity is in keeping with published data correlating severity of CRS with disease burden.