Engagement of 2B4 in dNK cells inhibits IFN-γ production. (A) Decidual and (B) peripheral mononuclear cells were cultured in the presence of rIL-2 and rIL-12 for 48 hours with an anti-CD48 blocking mAb (of IgM isotype) or, as control, with an isotype-matched irrelevant mAb. FSC indicates forward scatter. (C) Freshly purified dNK or (D) pNK cells were cultured in the presence of rIL-2 and rIL-12 for 48 hours and then incubated for an additional 18 hours either alone or cocultured with the CD48⁺ LCL 721.221 cell line. The NK/LCL 721.221 coculture was performed either in the presence of an anti-CD48 blocking mAb (of IgM isotype) or, as control, an isotype-matched irrelevant mAb. Analysis was performed by gating on CD3^–CD56⁺ cells. IFN-γ production by NK cells was evaluated by intracytoplasmic staining. The numbers represent the percentage of IFN-γ–producing NK cells.