Photostimulation of KIR2DL3 triggers retraction in primary human NK cells. KIR2DL3⁺ NK cells were stained with PKH26 and photostimulated on bilayers containing ULBP3, ICAM, and either HLA-Cw3(cage) or HLA-Cw3(Tyr). (left) A time-lapse montage (∼25-s intervals) showing a representative photostimulation experiment on a bilayer containing HLA-Cw3(cage). UV irradiation is indicated in magenta. (right) A graph showing the mean cell contact area before and after photostimulation on bilayers containing the indicated HLA-Cw3 proteins. The purple line denotes UV irradiation. Each curve was derived from ≥15 cells. Error bars show SEM. Data are representative of two independent experiments. norm., normalized. Bars, 5 µm.