The frequencies of HHV8-specific responses depend on the context and course of infection. (A) The number of patients with HHV8-specific CD8 T-cell responses were compared in 12 transplant recipients (□), 24 patients with AIDS-related KS (▪) and 12 patients with classical KS (▦) by chi-square test. The histograms show the percentages of patients with positive responses to the indicated peptide. (B) For each peptide, a representative example of the staining of the tetramer⁺ population is shown in the left panels, and grouped data for the frequency of the corresponding tetramer⁺ CD8 T cells are compared in the right panels. Boxes in the left panels delineate the tetramer⁺ CD8 T-cell population. The cut-off value for positive staining was defined by the mean + 2 SD frequency of tetramer⁺ cells in HLA-A2^–/HHV8⁺ patients. Horizontal bars represent the median percentages of tetramer⁺ cells. P values are shown for the comparison between the 3 patient groups (nonparametric Kruskall-Wallis test). (C) Comparison of anti-HHV8 responses in patients without KS (n = 8; □), patients with KS with persistent lesions (n = 18; ▪) and patients with KS in remission (n = 22; ▦). The results are the percentages of patients with positive responses to the indicated peptide. P values are shown for the comparison between the 3 groups.