Infusions of T cells and NK cells (Natural Killer) from peripheral blood are being carried out to treat malignancies. Lymphocytes propagated ex vivo, in normoxia (20% O2), are infused intravenously and must survive the hypoxia associated with venous circulation, bone marrow (5% O2) and the tumor microenvironment (1% O2). The main objective of this study was to determine the proliferative capacity of human T and NK cells in normoxia (20% O2) versus hypoxia (1% O2), for 28 days, using an artificial antigen-presenting cell (aAPC) for clinical grade propagation.