Decreased levels of circulating regulatory NK cells in patients with head and neck cancer throughout all tumor stages

Background: Natural killer (NK) cells play a crucial role in innate immunity as effectors against tumor cells and pathogen-infected cells. Human NK cells can be subdivided into two functional subsets, the immunoregulatory CD56^bright NK cells and the cytotoxic CD56^dim NK cells. NK-mediated host defence against tumor cells is strongly impaired in patients with head and neck squamous cell carcinoma (HNSCC). Materials and Methods: NK cells were isolated from peripheral blood of 70 HNSCC patients and 22 healthy donors by magnetic bead separation and subsequently analyzed using flow cytometric as well as immunohistochemical methods. Results: In this work we demonstrate that the population of circulating immunoregulatory CD56 ^bright NK cells is lower in the peripheral blood of patients with HNSCC as compared with that in healthy donors, regardless of the individual tumor stage or tumor type. Conclusion: These data underline the complex network of HNSCC-mediated immunomodulation as part of the immune escape mechanisms of malignant head and neck tumors.