SHIP-1–mediated catalytic activity is involved in the regulation of NK cell–mediated cytotoxicity.

Cultured human NK cells were left uninfected (no symbol) or infected with empty virus (▵) or with recombinant vaccinia virus encoding Flag-tagged SHIP-WT (■) and SHIP-ΔCAT (▪) and were assayed in a 4-hour ⁵¹Cr release assay against P815 targets in the presence of 5 μg/mL anti-CD16 mAb. Data are expressed as percent specific cytotoxicity ± SD obtained from 3 independent experiments. Overexpressed SHIP constructs in one representative experiment are shown (inset).