The association of HCMV infection with increased proportions of NKG2C+ cells has been reported in chronic lymphocytic leukaemia patients [30], solid organ and hematopoietic transplant recipients [31-33], a primary T-cell immunodeficiency [34], as well as in individuals coinfected by other pathogens, for example, HIV-1 [35-37], hantavirus [38], chikungunya [39], HBV, and HCV [40]. Moreover, NKG2C+ NK cells expanded in response to HCMV-infected fibroblasts in vitro, and it was hypothesized that the CD94/NKG2C activating KLR might recognize HCMV-infected cells [41]. Altogether, these observations are reminiscent of the pattern of

response to murine CMV (MCMV) specifically mediated by the Ly49H+ NK-cell subset [42] and, on that basis, it has been speculated that the CD57+ R788 mouse NKG2C+ subset might represent “memory” NK cells [32]. Interestingly, a complete deletion of the NKG2C gene has been reported in Japanese and European blood donors with ∼4% homozygosity and 32–34% heterozygosity rates [43, 44]; yet, whether

this genetic trait may influence the NK-cell PD0325901 chemical structure response to HCMV is unknown. In the present study, the relationship between congenital HCMV infection, NKG2C genotype, and NKR distribution was addressed. An immunophenotypic study was carried out in blood samples from children with evidence of past HCMV infection, either congenital symptomatic (n = 15), asymptomatic (n = 11), or postnatal Atazanavir (n = 11), and from noninfected children (n = 20). NKR expression (i.e., NKG2C, NKG2A, LILRB1, and CD161) was assessed by flow cytometry in NK (CD56+CD3−) and T cells (CD3+). Despite some differences in age distribution, both the proportions and the absolute numbers of NK and T cells were comparable in all four study groups (Table 1). Children with symptomatic congenital infection displayed higher proportions of NKG2C+ and lower percentages of NKG2A+ NK cells than asymptomatic or noninfected groups (Fig. 1). In contrast, the distributions of NKG2C+ and NKG2A+ NK cells were comparable in children with congenital symptomatic and postnatal infection. Remarkably, both the relative and absolute numbers

of LILRB1+ NK cells were markedly increased in symptomatic congenital infection, whereas no significant differences in the proportions of CD161+ NK cells were perceived (Fig. 1). Age, clinical features, and the proportions of NKG2C+ and LILRB1+ NK cells corresponding to cases of symptomatic congenital infection are displayed as Supporting Information Table 1. Multivariate analysis indicated that the immunophenotypic differences observed were independent of age. Studies in dizygotic twins further illustrated the impact of congenital symptomatic infection on the NKR repertoire (Table 2). In a first pair (TP1, 22 months old), only the HCMV-positive symptomatic boy displayed a marked increase of NKG2C+ and LILRB1+ NK cells as well as reduced proportions of NKG2A+ cells, compared to his noninfected sister.