Fig. 1.

HCV core_35–44 inhibits NKG2A⁺ NK cells only in the presence of an MHC class I leader peptide. (A and B) Stabilization of HLA-E on .174 cells, either in the absence of peptide or loaded with 0–100 µM HCV core_35–44 or HLA-G_sp, as determined by flow cytometry. The mean fluorescence intensity (MFI) of 3D12 staining is shown in the histograms (A) and is plotted against peptide concentration (B). (C) CD107a assay of NKG2A⁺ NK cells in response to 0–100 µM HCVcore_35–44 or HLA-G_sp alone or in combination. Dot plots are gated on CD3⁻ CD56⁺ CD158b⁻ lymphocytes. (D) CD3⁻ CD56⁺ NKG2A⁺ CD158b⁻ NK cell degranulation in response to increasing concentrations of HCV core_35–44 in the presence or absence of 1 µM HLA-G_sp. Data shown are the mean ± SEM of three independent experiments. (E and F) CD3⁻ CD56⁺ NGK2A⁺ CD158b⁻ NK cell degranulation to .174 cells loaded with HCV core_35–44 in the presence or absence of HLA-A2_sp or HLA-B7_sp for a healthy donor (E) and three HCV donors (F). (G) Cytotoxicity assay of sorted NKG2A⁺ NK cells using .174 targets incubated with the indicated peptides at an E:T ratio of 10:1. Data shown are the mean and SEM of three independent experiments from three different donors. (H and I) CD107a assay gating on NKG2A⁺ NKG2C⁻ NK cells stimulated with .174 cells loaded with the indicated peptides. One representative experiment is shown in H, and the mean + SEM from three independent experiments is shown in I. Slope difference P values in D, E, and F were calculated using linear regression comparing the difference the between the two lines. All other P values were calculated using one-way ANOVA.