NK/LAK-cell–mediated cytotoxicity against Fas⁺ and Fas⁻ tumor targets. NK/LAK cells from wild-type (A and D), gld/gld (B and E), and perforin-KO (C and F) mice were tested for cytotoxicity against L1210 Fas⁻ (A, B, C) or L1210 Fas⁺ (D, E, F) tumor targets. The cytotoxicity was performed as described in Fig 1.