Abstract: The present invention relates to expanded NK cells. The NK cells have been expanded ex vivo, are activated and have a cytotoxic phenotype. The cytotoxicity against malignant cells is markedly increased compared to non-expanded NK cells. The invention also relates to a method of treatment.

Abstract: A method of obtaining expanded and activated natural killer (NK) cells with the phenotype CD3?CD56+ and NK-like T cells with the phenotype CD3+CD56+ comprises providing a cell sample of peripheral blood from a tumor bearing subject; isolating cells from the blood sample and re-suspending the cells in growth medium; adding the isolated cells to a closed cell culture bag bioreactor at a concentration of about 0.5×106 to about 2×106/ml of growth medium; incubating and expanding the cells of step ii) with rocking motion agitation and heating until at least 50% of the expanded cell population comprises activated NK cells and NK-like T cells; and harvesting the expanded cell suspension of therapeutically active NK-cells and NK-like T cells from the bioreactor, wherein the cells exhibit an increased cytotoxicity compared to freshly isolated cells as determined by an in vitro cytotoxicity test.