LFA-1 blockade increases bystander killing. Live-cell confocal microscopy of antibody-dependent cellular cytotoxicity by eNK cells treated with murine IgG1 mAb control (A) or LFA-1 blocking mAb (clone TS1/22; B). Green, RTX-coated Raji cells (NK-inciting targets); yellow, uncoated Raji cells (bystanders); red, LysoTracker red (lytic granules); blue, SYTOX blue viability dye. NK cells were mixed with the target cells immediately before the imaging process and imaged every 4 min for 4 h. Quantitative analyses of viable cells are shown to demonstrate specific (C, left) versus nonspecific (C, right) killing by eNK cells. Data represent combined results from three healthy donors. Standard 4 h 51Cr cytotoxicity assay of NK cells treated with LFA-1–blocking mAb or murine IgG control (D). Each dot represents an individual healthy donor. Error bars show ± SD. *, P < 0.05; **, P < 0.01; ns, not significant.
