SUMMARY The allogeneic hematopoietic stem cell transplantation (HSCT) can cure intermediate and high-risk acute myeloid leukemia. Even with the development of strategies to reduce HSCT toxicity, this is still a complex treatment with high morbidity and mortality. Knowledge of the graft versus leukemia effect of HSCT has prepared the way for the development of Adoptive Immunotherapy or in vitro expansion of activated lymphocytes without alloreactivity, with subsequent intravenous infusion. The infusion of genetically modified T lymphocytes and haploidentical natural killer cells has been tested as an alternative to HSCT with very interesting results worldwide and in Brazil, as we not only have the technology of in vitro expansion of clinical grade lymphocytes available, but also do it according to the Good Manufacturing Practices that have been determined internationally.

Natural Killer cells are the first lymphocyte subpopulation to reconstitute after hematopoietic stem cell transplantation. Peripheral blood samples from thirteen patients who underwent allogeneic and autologous hematopoietic stem cell transplantation were analyzed at days 7, 14, 21 and 28 (± 2) after transplantation. Peripheral blood mononuclear cells were isolated using the Bulk Lysis™ EuroFlow standard operating protocol. They were stained for membrane markers with anti-CD45, anti-CD56, anti-CD16, anti-CD3, anti-CD14, anti-CD19, anti-CD2 and anti-CD7; and for intracellular cytokine detection with anti-IL-3, anti-GM-CSF and anti-TGF-1β. On day 7, the presence of Natural Killer cells was detected in 9 patients (mean: 11.6%, SD±: 6.3 of lymphocytes) as well as on day 14 (mean: 16.3%, SD±: 8.2), day 21 (mean: 31.6%, SD±: 9.5) and day 28 (mean: 22.7%, SD±: 6.1). An increase in CD56+16+ phenotype recovery was observed at days 21 (mean: 22%, SD±: 7.2 of lymphocytes, range: 8.0 – 36.1) and 28 (mean: 16%, SD±: 4.9, range: 6.6 – 25.7) when it was compared with CD56bright and CD56+16- (p<0.05). The production of cytokines IL-3, GM-CSF and TGF-β1 was observed during the recovery period of Natural Killer cells within 28 days after transplantation (p=0.04). These data suggest that Natural Killer cells have the ability to produce hematopoietic growth factors and related cytokines which may contribute to the reestablishment of hematopoiesis after transplantation, prevent graft-versus-host disease and enhance the engraftment.