Ex-vivo expanded cells from elutriated cell fractions efficiently lyse allogeneic prostate cancer cells. PBMC and elutriated fractions 2, 3 and 4 from the same healthy individual were expanded ex-vivo in the presence of K562-mbIL15-41BBL and IL-2 for 14 days and then tested for in vitro cytolytic activity. Cytolytic activity was evaluated in 4 hour 51Cr release assays against (A) prostate cancer (DU-145, PC-3 and LNCaP) cells. Ex-vivo expanded cells from elutriated cell fractions 2 (◇), 3 (△) and 4 (□) lysed prostate cancer cells in a similar fashion as ex-vivo expanded cells from PBMC (○). (B) Elutriated cell fractions become enriched in NK cells (defined by CD56+CD3- cells) after 14 days of culture regardless the cellular content of these fractions. The mean percentage cytotoxicity is shown from triplicate wells from one representative experiment. Bars represent the SD. Experiment shown represents one of four individual experiments.