CD16 or anti-β2-integrin engagement on human NK cells induces WASp tyrosine phosphorylation. Human NK cells were left untreated (-) or were stimulated with anti-β2 (TS1/18), anti-CD16 (B73.1), or anti-CD56 (C218) mAb-coated polystyrene beads for the indicated time periods at 37°C. Cell lysates were immunoprecipitated with anti-WASp mAb. The resultant protein complex was resolved by 7% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), transferred to nitrocellulose, and sequentially immunoblotted with anti-pTyr (4G10) mAb (top) and anti-WASp antiserum (bottom). Sizes are indicated in kilodaltons, and the arrow indicates the position of WASp. These results represent 1 of 3 independent experiments.