Immunophenotypes of EBV-specific CTLs. (A) Phenotypic composition of CTL lines. Percentages of CD3⁺, CD4⁺, and CD8⁺ T cells, natural killer cells (CD3⁻CD56⁺), and residual CD19⁺ B cells are shown. Each symbol represents a cell line infused into a single subject. (B) Expression of naive, central memory, and effector memory surface markers on CD4⁺ and CD8⁺ populations of the 20 most recently generated EBV-CTL lines.