Functional avidity of CMV-specific T cells. CMV-specific T cells were incubated for 5 hours with 10-fold serial dilution of cognate peptide epitopes. IFN-γ expression was then assessed using an intracellular cytokine assay. Representative flow cytometric analysis after stimulation of ELR/K, VTE, NLV, or IPS-specific T cells with serial dilutions of cognate peptide.