CD69 expression by BMLF1- and pp65-specific CD8⁺ T cells at initiation of culture. Percentage of CD69⁺ cells within BMLF1-specific, pp65-specific, and total CD8⁺ T cells. Staining was performed on PBMCs from EBV- and CMV-seropositive HLA-A2 donors (mean ± SE, n = 5).