Cytotoxicity of CI/NKG2^- NK cells. B6 mice were depleted of CI/NKG2⁺ NK cells by treatment with a mixture of the SW5E6 and 16a11 mAbs. The SW5E6 and 16a11 mAbs routinely deplete 95% or 80%, respectively, of the corresponding NK-cell subsets (data not shown). Control NK-cell populations were depleted of irrelevant Ly49A⁺ and Ly49G2⁺ NK cells by treatment with A1 and 4D11 mAbs, or were from untreated mice. The NK-cell populations were tested for lysis of β2m^-/- Con A blasts (left) or B6 Con A blasts (middle), or, in a separate experiment, YAC-1 tumor cells (right). The effector-target (E/T) ratio was calculated according to the number of NK1.1⁺CD3^- cells in the population. Each experiment was repeated with comparable results. Splenocytes from CI/NKG2^--depleted mice were significantly less cytotoxic than both Ly49A/Ly49G2-depleted or control mice against β2m^-/- Con A blasts (P ≤ .008 at 6:1 or 3:1 E/T ratios) or YAC-1 targets (P ≤ .03 for all E/T).