KB tumor cells were treated with C-IgG– or F-IgG–FITC for 30 min at 37°C and collected at the designated time points. Cells were washed with flow buffer (5% FBS in PBS), fixed in 1% formalin in PBS, mounted on 25 × 75 × 1 mm slides (Erie Scientific, Portsmouth, NH) and stained with DAPI for nuclear identification (Vector Labs, Burlingame, CA) prior to analysis by immunofluorescence (IF) microscopy. Intracellular analysis of NK cell ERK phosphorylation was also assessed following coculture with KB tumor cells. NK cell activation was assessed 48 hours post coculture via FACS analysis with CD56‐phycoerythrin (PE), CD158-allophycocyanin (APC), CD57‐FITC, NKG2A-PE (Beckman Coulter, Brea, CA), CD56‐APC, CD3‐V450, CD16‐FITC, NKG2D-APC, CD69–phycoerythrin-cyanin 7 (Pe-Cy7) and KIR/NKAT2‐FITC, CD94‐APC, NKp46/CD335-APC antibodies (BD Biosciences, San Jose, CA). In murine studies, IF microscopy of tumor sections was performed (16 (link)). Sections were analyzed on an Olympus Fluoview 1000 laser scanning confocal microscope. In murine studies with C‐IgG– and F‐IgG–FITC, tissues were harvested in the dark at indicated times. Tumors were dissociated (17 (link)) and stained with FR‐α–APC (R&D Systems, Minneapolis, MN). FR+/FITC+ populations were assessed using a Becton Dickinson FACS Calibur flow cytometer (Becton‐Dickinson, San Jose, CA) (16 (link)).