Inclusion Criteria for Procurement and T-cell Production:

          -  Age ≤21 years old

          -  Relapsed/refractory CD123+ disease defined as follows:

        AML

          -  Relapsed disease: Patients developing recurrent disease after a first complete
             remission (CR)

          -  Refractory disease: Patients not achieving a CR after 2 cycles of induction
             chemotherapy

        B-cell ALL

          -  Relapsed disease that is CD123 positive and CD19 negative/dim or patients otherwise
             ineligible for CD19 directed therapies including

               -  Patients in 2nd or greater relapse

               -  Patients with relapse after allogeneic HSCT

          -  Refractory disease that is CD123 positive and CD19 negative/dim or patients otherwise
             ineligible for CD19 directed therapies

        T-cell All • Relapsed refractory disease that is CD123 positive

        BPDCN

        • Relapsed/refractory disease that has failed front-line therapy

          -  Estimated life expectancy of >12 weeks

          -  Karnofsky or Lansky (age-dependent) performance score ≥50

          -  Patients with a history of prior allogeneic HCT must be clinically recovered from
             prior HCT therapy, have no evidence of active GVHD and have not received a donor
             lymphocyte infusion (DLI) within the 28 days prior to apheresis

          -  Patient must have an identified, suitable HCT donor

          -  For females of child-bearing age:

          -  Not lactating with intent to breastfeed

          -  Not pregnant with negative serum pregnancy test within 7 days prior to enrollment

          -  Meets eligibility criteria to undergo autologous apheresis, or have previously
             undergone autologous apheresis

        Exclusion Criteria:

          -  Known primary immunodeficiency

          -  History of HIV infection

          -  Severe intercurrent uncontrolled bacterial, viral or fungal infection (e.g. active
             hepatitis B or C infection or adenovirus infection)

          -  History of hypersensitivity reactions to murine protein-containing products

          -  Patients with acute promyelocytic leukemia (APL, t (15;17))

          -  Known contraindication to the protocol defined lymphodepleting chemotherapy regimen of
             fludarabine/cyclophosphamide.

        Inclusion Criteria for Treatment:

          -  Age≤21 years old

          -  Detectable disease that is CD123+ (at least MRD+ disease)

          -  Estimated life expectancy of >8 weeks

          -  Karnofsky or Lansky (age-dependent) performance score≥50

          -  Patients with a history of prior allogeneic HCT must be clinically recovered from
             prior HCT therapy, have no evidence of active GVHD and have not received a donor
             lymphocyte infusion (DLI) within the 28 days prior to planned infusion

          -  Patient must have an identified, suitable HCT donor

          -  Adequate cardiac function defined as left ventricular ejection fraction >40%, or
             shortening fraction ≥25%

          -  EKG without evidence of clinically significant arrhythmia

          -  Adequate renal function defined as creatinine clearance or radioisotope GFR ≥50
             ml/min/1.73m2 (GFR ≥40 ml/min/1.73m2 if < 2 years of age)

          -  Adequate pulmonary function defined as forced vital capacity (FVC)≥50% of predicted
             value; or pulse oximetry≥92% on room air if patient is unable to perform pulmonary
             function testing

          -  Total Bilirubin≤3 times the upper limit of normal for age, except in subjects with
             Gilbert's syndrome

          -  Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≤5 times the upper
             limit of normal for age

          -  Has recovered from all NCI CTAE grade III-IV, non-hematologic acute toxicities from
             prior therapy

          -  For females of child-bearing age

               -  Not lactating with intent to breastfeed

               -  Not pregnant with negative serum pregnancy test within 7 days prior to enrollment

          -  If sexually active, agreement to use birth control until 3 months after T- cell
             infusion. Male partners should use a condom.

          -  Available autologous transduced T-cell product that has met GMP release criteria

        Exclusion Criteria:

          -  Known primary immunodeficiency

          -  History of HIV infection

          -  Severe intercurrent uncontrolled bacterial, viral or fungal infection

          -  History of hypersensitivity reactions to murine protein-containing products

          -  History of severe hypersensitivity reactions to cornstarch or hydroxyethyl starch.

          -  Receiving systemic steroids therapy exceeding the equivalent of 0.5 mg/kg/day of
             methylprednisolone, in the 7 days prior to CD123-CAR T- cell infusion

          -  Receiving systemic therapy in the 14 days prior to CD123-CAR T-cell infusion, which
             will interfere with the activity of the CD123-CAR T cells in vivo (in the opinion of
             the study PI(s))

          -  Receiving rituximab therapy in the 30 days prior to CD123-CAR T cell infusion. (This
             exclusion criterion is intended to prevent premature exposure of CD123-CAR Tcells to
             rituximab, which would activate the safety switch and promote CAR T-cell apoptosis).

          -  Receiving intrathecal chemotherapy in the 7 days prior to CD123-CAR T cell infusion.

          -  Known contraindication to the protocol defined lymphodepleting chemotherapy regimen of
             fludarabine/cyclophosphamide.

          -  Active CNS disease