Next, we set out to determine the phenotypic characteristics of NKG2C+CD56dim NK cells from the present patient cohort. Because our data suggested that expansion of NKG2C+ NK cells was dependent on HCMV infection, we choose to perform an aggregate analysis of NKG2C+ NK cells in patients with HCV and HBV. Significantly fewer click here NKG2C+ CD56dim NK cells expressed NKG2A, CD161, Siglec-9, and NKp30 compared with NKG2C− CD56dim NK cells (Fig. 1C). In contrast, NKG2C+

NK cells more commonly expressed ILT2, CD57, and CD2. Percentages or MFI of CD62L, CD8, NKG2D, CD16, and DNAM-1-positive cells were indistinguishable when comparing NKG2C+ and NKG2C− NK-cell subsets (Fig. 1C and Supporting Information 2). The expression pattern of cytolytic molecules in the granules of CD56dim NK cells revealed that both Granzyme A and perforin were expressed at equivalent levels in NKG2C+ and NKG2C− NK cell subsets. In contrast, expression of Granzyme B was higher and Granzyme K lower in NKG2C+, compared with NKG2C− NK cells (Fig. 1D). Importantly, the phenotype of NKG2C+ NK cells was identical in HCV- and HBV-infected individuals (data not shown). Together, these data show that NKG2C+ NK cells have a full cytolytic arsenal and a highly differentiated phenotype, as defined by the

high expression of CD57. To examine the functionality of the NK cells and its relation to their expression of NKG2C, we separated them into three subsets: NKG2A+NKG2C−, NKG2A−NKG2C−, and NKG2A−NKG2C+ NK cells. We simultaneously assessed these subsets Dactolisib in the presence of various target cells for multiple functional responses. NKG2C+NKG2A− NK cells derived from patients with HBV or HCV infection displayed

stronger and more diverse functional responses than NKG2C− NK subsets following stimulation with targets expressing HLA-E, and against RAJI cells in the presence of anti-CD20 mAb (Fig. Etomidate 2A). In agreement with the prominent role for NKG2A in NK cell education 8, 29, NKG2A+ NK cells responded better than NKG2A− NK cells, regardless of their NKG2C expression, against both MHC class-I-negative K562 and 721.221 target cells. Furthermore, NKG2A+ NK cells produced high levels of IFN-γ in response to stimulation with IL-12/IL-18 (Fig. 2B), while IFN-γ production was almost undetectable in the NKG2C+CD56dim subset. Together, these results demonstrate that NKG2C+ NK cells display a functional profile similar to highly differentiated NK cells, shown to have a high responsiveness via ADCC but poor ability to respond to exogenous cytokines 30, 31. Extending previous results, we here show that differentiated NKG2C+ NK cells are polyfunctional and respond strongly to specific stimulation by HLA-E expressing target cells. Of note, NKG2C+ NK cells were also present in the liver (Supporting Information 3A). NKG2C+ NK cells in the liver were mostly NKG2A− and responded to stimulation with HLA-E expressing 721.221 target cells but not against control 721.