Effects of a PLDN mutation on NK-cell function. (A) Histograms of flow cytometric measurement of CD63 and CD107a on IL-2–activated NK cells from a normal control subject, the pallidin-deficient patient, and a patient with HPS2. (B) Two-color flow cytometric measurement of CD107a and CD56 on IL-2–activated NK cells from the pallidin-deficient patient, after transfection with expression vectors containing GFP or PLDN and GFP. (C) Two-color flow cytometric measurement of CD107a on IL-2 activated NK cells from a normal control subject and the pallidin-deficient patient, after culture with medium or with target cell line LCL.721.221. (D) Lysis of K562 NK target cells by freshly isolated PBMCs from the pallidin-deficient patient and a healthy control before and after overnight incubation with IL-2. Experiments were repeated 3 times in 3 independent experiments.