Cytotoxicity of the CD34⁺ EB cell–derived LAK cells to NK-sensitive Yac-1 cells and NK-resistant P815 cells. The cytotoxicity of spleen LAK (A), type I LAK (LAK34a-1) (B), LAK34a-3 (D), and type II LAK (LAK34a-2) (C) effector cells was compared by the⁵¹Cr release assay. A fixed number of⁵¹Cr-labeled target cells, Yac-1 (○, •) and P815 (▵, ▴), were mixed with different numbers of effector cells, and incubated for 4 hours (○, ▵), or 18 hours (•, ▴). Averaged values of percent specific killing are shown with the corresponding standard deviation (vertical line).