Acquisition and loss of CCR7 by NK cells cocultured with CCR7/GFP cell transfectants. (A-C) In these experiments, polyclonal IL-2–activated NK cells that had been cultured for 1 hour either in the presence of HEK293 or HEK293-GFP (top panel) or in the presence of HEK293-CCR7/GFP (middle panel) were assessed for CCR7 expression by cytofluorimetric analysis. NK cells that had acquired the CCR7⁺ phenotype upon interaction with HEK293-CCR7/GFP transfectants were analyzed by immunofluorescence for the expression of GFP (bottom panels). Data are representative of 5 independent experiments performed using different donors. (B) Adherent CCR7/GFP⁺ CHO cell transfectants were used for induction of CCR7 on polyclonal IL-2–activated NK cells in a 1-hour coculture. Then NK cells were isolated, cultured in the absence of CCR7⁺ cells, and analyzed at different time intervals for the expression of surface CCR7. Data are representative of 3 independent experiments performed using different donors. (C) Confocal images of CCR7/GFP transfer from CCR7/GFP⁺ HEK293 cells to NK cells. Polyclonal IL-2–activated NK cells were mixed with CCR7/GFP⁺ HEK293 cells; after 15- to 30-minute incubation at 37°C, cells were collected, laid onto poly-lysine slides, fixed, and stained with anti-CD11a mAb. Samples were analyzed by dual-image confocal microscopy. (Ci-iv) Green fluorescence (GFP); (Cii,v) red fluorescence (CD11a); (Ciii,Cvi) merge.