IL-10 in the microenvironment of HNSCC inhibits the CpG ODN-induced IFN-α secretion of pDCs

It has been shown that head and neck squamous cell carcinoma (HNSCC) is infiltrated by plasmacytoid dendritic cells (pDCs). The HNSCC TH2 biased microenvironment leads to strong alterations of the cellular functions of pDC and thus impairs the initiation and function of adequate immune responses. In this work we comprehensively analyzed the capacity of CpG-oligonucleotides to activate interferon (IFN)-alpha secretion of human pDC in the presence of HNSCC. IFN-alpha secretion was measured using the ELISA Technique. Class A CpG dinucleotide 2216 was used in different concentrations and time frames to stimulate the IFN-alpha production of human pDC from peripheral blood in the absence and presence of the HNSCC microenvironment. To elucidate single components that might induce the reduction of IFN-alpha secretion, pDC were exposed to different concentrations of HNSCC relevant cytokines such as IL-6, IL-8 and IL-10. In accordance to former experiments we found that HNSCC micro milieu severely depresses up to 75% of IFN-alpha secretion capacity of pDCs, if the stimulating Class A CpG 2216 is added to the culture. Preincubation of HNSCC supernatant leads to unrestorable reduction of IFN-alpha secretion in pDC and can not be restored by CpG 2216. Incubation of pDCs with single cytokines relevant for cancer progression within the HNSCC micro milieu show that IL-6 or IL-8 have no influence on the IFN-alpha secretion in pDCs, whereas IL-10 massively impairs the secretion in a dose dependent manner. This effect can be potentiated by synergistic incubation with IL-6 and can be abrogated by blocking antibodies to the IL-10 receptor. Interestingly, incubation with IL-10 is not the only factor that impairs the IFN-alpha secretion, as incubation with the whole HNSCC supernatant is even more effective in reducing the secretion, implying that additional factors play a role. We conclude that restoration of HNSCC induced TH2 bias could be improved by the inhibition of immune cell cytokine receptors in addition to immunostimulating approaches with CpG motifs.