Figure 6
IL-21 downregulated cell surface expression of NKp44 and NKG2D and expression of DAP10 and DAP12. (a) IL-21 downregulated NKp44 and DNAX-activating protein of 12 kDa (DAP12). The percentage of natural killer (NK) cells expressing NKp44 at the cell surface after addition of IL-21 to IL-15 (left) was diminished. Simultaneously, transcripts of the adaptor DAP12 were quantified by real-time PCR after 7 days of culture with IL-15 and compared with the same culture conditions when IL-21 was added (right). The results indicate a reduction in DAP12 transcripts after addition of IL-21 compared with day 0. The expression of DAP12 cDNA was normalized against the housekeeping gene 18S. Mean ± standard deviation of three experiments is shown. (b) IL-21 downregulated DAP12 at the protein level. NK cells were purified by magnetic beads and cultured with IL-15 in presence or absence of IL-21. After 7 days of culture, the adaptor DAP12 protein was quantified by Western blot. The blots were probed with anti-DAP12 and anti-β-tubulin antibodies. (c) IL-21 downregulated NKG2D and DAP10. The percentage of NK cells expressing NKG2D at the cell surface after addition of IL-21 to IL-15 (left) is shown. Simultaneously, the adaptor DAP10 transcripts were quantified by real-time PCR after 7 days of culture with IL-15 and compared with the same culture condition when IL-21 was added (right). As previously shown by Burgess and coworkers [24], in the presence of IL-2, IL-21 down-regulated the expression of C-lectin receptor NKG2D at the cell surface and the transcript of the adaptor DAP10 after 7 days of culture with IL-15. The expression of DAP10 cDNA was normalized against the housekeeping gene 18S. Mean ± standard deviation of three experiments is shown.