2B4 inhibits the dNK-mediated killing of CD48⁺ B-cell lines. (A) CD48 surface expression by LCL 721.221, Daudi, and FO1 cell lines (mean fluorescence intensities were 710, 75, and 4.5, respectively). Gray profiles represent negative controls. (B) Polyclonally activated pNK or (C) dNK cells were analyzed for their cytolytic activity against LCL 721.221, Daudi, and FO1 target cell lines in either the absence or presence of mAbs specific for 2B4 or CD48. The E/T ratio used was 5:1. Both mAbs used in these experiments were of the IgM isotype. Similar results were obtained in 5 independent experiments.