(A) YTS KIR2DL1 cells were incubated with SHP-1 and Cbls siRNA-loaded NPs (red curve) or empty NPs (purple curve). After 48 hours, cells were loaded with Fluo-3-AM and analyzed for intracellular calcium levels for 20 min at 37°C. YTS KIR2DL1 cells that were treated with PBS served as a negative control (green curve). NK cells that were mixed with 721.221 Cw7 target cells served as a positive control (blue curve). Calcium levels were analyzed by spectrofluorometry. (n=3) 