Simultaneous detection of several antigen-specific populations. (A) A panel including tetramers specific for MART1_26-35, HIV Gag p17_77-85, CMVpp65_495-503, and influenza A–M1_58-66 HLA-A2.1 tetramers was developed. All tetramers were labeled with PE, and a second tetramer labeled by a unique fluorochrome was used, as indicated. (B) Simultaneous enrichment was performed using anti-PE microbeads. Within the global PE-enriched tetramer-positive population, each specificity was identified using the second tetramer label. (C) The cell phenotype of the tetramer-positive cells was then analyzed using anti-CD45RA and anti-CD11a antibodies.