MHC tetramer analysis and intracellular IFN-γ analyses of pp65-derived CMV-specific T cells. CMV-specific T-cell lines of HLA-A*0201⁺ individuals were generated by stimulation of purified CD3⁺ cells with DCs pulsed with pentadecapeptide 123, containing the NLVPMVATV sequence. (A) Staining with HLA-A*0201–restricted MHC tetramer complexed with NLVPMVATV peptide. (B) Intracellular IFN-γ production after overnight stimulation with K562/A*0201 pulsed with NLVPMVATV peptide or the pentadecapeptides 123 or 121. The percentages of CD8⁺ CD69⁺ IFN-γ⁺ cells or CD8⁺ tetramer⁺ cells are shown in the right upper quadrant.