Correlation between CMV epitope-specific T-cell frequency, T-bet expression, and CD27/CD57 expression by CMV-specific T cells. PBMCs from CMV-seropositive donors were stained with CMV-specific pMHC multimers, followed by fluorescently labeled anti-CD8-, CD27-, and CD57-specific antibodies. (A) Representation multimer analysis from 4 donors. (B) Data represent the mean ± SEM of pMHC multimer-specific CD8⁺ T cells in HLA-matched PBMCs. (C) Data represent the correlation between the frequency of pMHC multimer-specific cells and T-bet mean fluorescent intensity. (D) Data represent the mean ± SEM of epitope-specific T cells displaying either an early memory (CD27⁺CD57⁻) or late/terminal (CD27⁻CD57⁺) phenotype. (E) Data represent the correlation between the frequency of pMHC multimer-specific cells and the proportion of those cells expressing a late/terminal (CD8⁺CD27⁻CD57⁺) memory phenotype. (F) PBMCs from CMV-seropositive donors were stained with CMV-specific pMHC multimers, followed by fluorescently labeled anti-CD8, CD45RA, CCR7, PD1, LAG3, TIM3, NKG2A and NKG2C antibodies.