Differentiation phenotypes of HHV-8 CD8⁺ T cells. Flow cytometric analysis of CD45RA, CCR7, and CD27 coexpression gated on IFN-γ–producing CD8⁺ PBMC after stimulation with appropriate HHV-8 epitopes as detected in the ELISpot-IFN-γ assay, and performed as described in “Methods.” (A) Individual percentage of CD8⁺ cells producing IFN- as assessed by intracellular cytokine staining after HHV-8 peptide stimulation. PBMC were stimulated by 1-10 HHV-8–specific peptides in the same tube. Each symbol represents a separate patient, with the shape corresponding to the disease form (the 2 rhombuses represent 2 patients with active MCD; the 4 circles, 4 patients with MCD in remission; the 7 squares, 7 AC). (B) Subsets of virus-specific CD8⁺ T cells producing IFN-γ. Each symbol represents a different patient, with shapes corresponding to disease form as in panel A. Only relevant IFN-γ–secreting CD8⁺ populations are depicted (CCR7⁻CD27⁺CD45RA⁻, CCR7⁻CD27⁻CD45RA⁻, and CCR7⁻CD27⁻CD45RA⁺ CD8⁺ IFN-γ⁺ cells, corresponding to early and intermediate, late effector, and fully differentiated effector memory cells). Median percentages of other populations were lower than 1% of CD8⁺ IFN-γ⁺ cells. The Mann-Whitney nonparametric test was used to compare groups. (C) Each display represents cytometric images for CD8^hi+ IFN-γ⁺ cells, and their corresponding complete CCR7, CD27, and CD45RA phenotype. Proportions of cells in each quadrant are presented in the labels. Nonstimulated cells, HHV-8 peptide– and EBV peptide–stimulated cells are depicted, respectively. Each display represents a representative donor from each group.