NK activity of freshly isolated cord blood and BM mononuclear cells. (▪) Cord blood (n = 9) and (□) BM (n = 7) mononuclear cells were isolated by lymphoprep gradient centrifugation. Cells were washed and set up in a ⁵¹Cr release assay at the E:T cell ratios indicated. Bars show the % kill + 1 standard deviation (SD). Data were compared using the Mann Whitney statistical test.