Enrichment of tetramer-specific CD8⁺ T cells. (A) Tetramer staining of PBMCs (first row) and enriched cells after 7 days of expansion (second row) from one donor (LSA4). Tetramers are complexes with the pp65-peptide NLV (third column) or with the IE-peptide VLE (fourth column). The percentages of tetramer-binding CD3⁺/CD8⁺ lymphocytes are indicated. (B) Diagrams show the percentages of tetramer binding CD3⁺/CD8⁺ lymphocytes from all 8 donors before enrichment (day 0 [d0]) and at d7 after enrichment and expansion. Tetramers were complexed with the peptides NLV (•), VLE (), and TPR (▴).