Functionally active CMV-specific CD4⁺ and CD8⁺ T cells are enriched after selection and expansion. (A) IFN-γ staining of PBMCs (top row) and enriched cells after 7 days of expansion (bottom row) from one donor (LSA5). Cells were stimulated with CMV lysate (second column), pp65-peptide NLV (third column), or IE-peptide VLE (fourth column). (B) Absolute numbers of IFN-γ-positive CD4⁺ lymphocytes after CMV lysate stimulation are shown from 4 donors—LSA4 (▪), LSA5 (□), LSA6 (▴) and LSA9 (▵)—before enrichment (d0) and after enrichment and 10 days of culturing (d7). (C) Absolute numbers of IFN-γ-positive CD8⁺ lymphocytes after stimulation of PBMCs (d0) and cells after enrichment and 10 days of culturing (d10) with the cognitive peptides. Cells were taken from the same donors as in panel B.