Fig. 1.

Neutrophils impair the cytotoxicity and infiltration capability of NK cells. (a) Comparison of cytotoxicity of NK cells from tumor-bearing mice and naïve mice. NK cells were isolated from blood or spleen of naïve (N) and tumor-bearing mice (T), and cytotoxicity was measured as described in Materials and Methods. (b) The effect of tumor-associated neutrophils (TANs) on the cytotoxicity of NK cells. Peritoneal neutrophils isolated from naïve mice or CT-26 bearing mice were adoptively transplanted into naïve mice, and cytotoxicity of NK cell was determined as described in Materials and Methods. (c) Comparison of the infiltration of NK cells from tumor-bearing mice and normal mice. NK cells were isolated from spleen and blood of tumor-bearing mice and normal mice, stained with carboxyfluorescein succinimidyl ester (CFSE), and the labeled cells were injected into tumor-bearing mice through the tail veil. The tumor sections were analyzed to assess NK cell infiltration using fluorescence microscope. (d) The effect of TANs on the infiltration of NK cells. Peritoneal neutrophils isolated from naïve mice or tumor-bearing mice were adoptively transplanted into tumor-bearing mice, and NK cell infiltration was determined by immunohistochemistry (IHC), brown: NK cells (DX5 positive), blue: cell nuclei (hematoxylin staining). Results are expressed as mean ± standard deviation (SD) from three independent experiments (n = 8 in each group). *p < 0.05. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)