Figure 5.

CD16 is maintained of the surface of 1106mel-expanded NK cells due to antibody recognition. (A, B) Sera from four different donors were incubated with (A) 721.221 cells or (B) with 1106mel cells. Detection of the sera binding to the cells was performed by anti-human IgG (black-line histograms). Staining with 10% fetal calf serum was used as negative control (gray-filled histograms). (C) 1106mel cells were stained either with complete human serum (red line) or with IgG-depleted serum (blue line). (D) NK cells were incubated with 1106mel in the presence of the complete sera (left) or following depletion of IgG (right). Data shown are representative of three independent experiments. (E) Freshly isolated NK cells were incubated either with a control mAb or with the anti-CD16 mAbs (3G8) and then cocultured with irradiated 1106mel cells. Five days later, the cells were stained for CD16 expression. The numbers in the figure indicates the percentages of CD16⁺ cells. Data shown are representative of two independent experiments. (F) CD16 levels in the supernatants of NK cells (incubated with 1106mel in presence or absence of 3G8 mAb) were quantified by ELISA five days following the coculturing. Data are shown as mean + SD of four replicates from one of two experiments performed. ** p < 0.02 (by two tailed Student’s t-test). (G) Freshly isolated NK cells were cultured with 221/CEA in the absence (left) or in the presence (middle) of polyclonal anti-CEA Abs or with 1106mel (right) and stained 5 days later for CD16 expression. The numbers in the figure indicates the percentages of CD16⁺ cells. (H) CD16 levels in the supernatants of NK cells (incubated with 221/CEA in presence or absence of anti-CEA polyclonal Abs) were quantified by ELISA after 5 days and shown as mean + SD of four samples/replicates from two experiments. *p < 0.04, (by two tailed Student’s t-test).