T-cell phenotype of pp65-specific T cells. Markers of T-cell maturation, CD27, CD28, CD62L, and CD45RO, were analyzed among CD3⁺CD4⁺ and CD3⁺CD8⁺ double-positive gated cells after the isolation procedure. The analysis of T-cell subpopulations showed a mixed Ag-specific T-cell graft, according to the expression of CD27 and CD28. Both early double-positive and late double-negative T cells were among the CD4⁺ and CD8⁺ subgroups. Naive T cells were defined as CD45RO⁻ CD62L⁺, central memory T cells as CD45RO⁺ CD62L⁺, and effector memory T cells as CD45RO⁺ CD62L⁻.