To determine safety profile of immunotherapy with natural killer cells and activated expanded (NKAEs) after salvage chemotherapy in children, adolescents and young adults with relapsed or refractary acute leukemia

Inclusion Criteria:

1. Patients between 0 and 23 years of age with diagnosis of acute lymphoblastic leukemia, in second relapse situation, posttransplant relapse or refractary, or
2. Patients between 0 and 23 years of age with diagnosis of acute myeloblastic leukemia, relapsed or refractary. (Patient must meet inclusion criteria 1 or 2)
3. Lansky index > 60%
4. Mild (<2) functional organs alteration (hepatic, renal, respiratory) according to National Cancer Institute criteria (NCI CTCAE v4).
5. Left ventricular ejection fraction > 39%
6. To grant informed consent in accordance with the current legal regulations.
7. Presence of a compatible haploidentical donor (father or mother or brother).

Exclusion Criteria:

1. Patients with history of bad therapeutical compliance
2. Patients not valid after psycho-social evaluation
3. Positive HIV serology