Human Dex harbour functional IL-15Rα and synergize with IL-15 for NK cell proliferation <i>in vitro</i> and IFNγ production <i>in vitro.</i>

<p><i>A.</i><i> Immunoblotting of IL-15Rα from Dex and DC lysates</i>. Western Blot analysis on 10–40 µg of protein lysates obtained from immature DC (iDC), Dex or Tex (exosomes from Mel888 melanoma cell line) using anti-IL-15Rα mAb. Positive controls included anti-HLA-DRα, -TSG 101 and -HSC 70 Abs. Representative immunoblots of two normal volunteers are depicted (NV1 and NV2). Molecular weights are indicated on the left lane. B. <i>Proliferative effects of recombinant IL-15 and Dex on NK cells</i>. CFSE-labeled NK cells were cultured with or without 10 µg autologous Dex or allogenic Tex in complete medium containing 0.5 ng/ml of human recombinant IL-15. At day 6 of culture, NK cell proliferation was determined by flow cytometry and the number of divisions were counted and depicted. A representative experiment out of two is shown. C–D. <i>Synergistic effects between Dex and recombinant IL-15 for NK cell triggering</i>. NV's PBL were cultured without (white histograms) or with (black histograms) 10 µg autologous Dex and increasing concentrations of human recombinant IL-15. NK (CD56⁺ CD3⁻) cells were then analysed for CD69 expression by flow cytometry (C) or supernatants were harvested to measure IFNγ levels in EIA (D). The graphs depict means±SEM of % of CD69 expressing NK cells in 3 experiments (C) or IFNγ concentrations in 4 experiments (D). * p<0.05, ** p<0.01 and ns: non significant.