Polarization of secretory lysosomes in Stx11-deficient resting NK cells. Resting NK cells from a FHL4 patient mixed with K562 target cells. Cells were fixed, permeabilized, and stained with antiperforin mAb (red) and DAPI (blue). Left panel shows a differential interference contrast (DIC) image. The right panel shows overlay of nuclear staining with DAPI and antiperforin mAb. Scales represent 5 μm.