Fig. 6.

The inhibition of neutrophils on NK cells was dependent on direct cell-cell contact. (a) The effect of neutrophils on the cytotoxicity of NK cells. Neutrophils and NK cells were isolated from naïve or tumor-bearing mice, 1 × 10⁵ NK cells were co-cultured with neutrophils at the indicated ratios for 6 h, and then incubated with YAC-1 cells (1 × 10⁵). NK cells cytotoxicity was detected as described in Materials and Methods. (b) The effect of neutrophil-NK cell contact on NK cell cytotoxicity. Neutrophils and NK cells were co-cultured in a direct contact in a well or in different chambers of a transwell system, and NK cell cytotoxicity was detected as described in Materials and Methods. Results are expressed as mean ± SD from four independent experiments (n = 6 in each group). *p < 0.05, **p < 0.01.