CD8⁺ T-cell recognition of target cells sensitized with CPS or FPT epitopes using either viral infection or synthetic peptides. (A) MRC-5 cells expressing HLA B*3508 were infected with HCMV at an MOI of 5:1 and then exposed to CPS- or FPT-specific T cells (responder to stimulator ratio of 2:1) at different time intervals (indicated on x-axis). At each time point, T cells were assessed for IFN-γ expression using intracellular cytokine assay. Data presented here is summary of 3 different experiments based on 3 different HLA B*3508⁺ donors. (B) CTL recognition of HLA B*3508 expressing target cells sensitized with synthetic CPS and FPT peptide epitopes. MRC-5 cells expressing HLA B*3508 were sensitized with serial dilutions of the peptides and then exposed to CPS- or FPT-specific CTL lines. These clonal T cells were derived from donor 1. (C) MRC-5 cells expressing HLA B*3508 were sensitized with synthetic CPS- or FPT-peptide epitopes (1 μg/mL) and then exposed to CPS- or FPT-specific T cells (responder to stimulator ratio of 2:1) for 16 to 18 hours. T cells were assessed for IFN-γ expression using intracellular cytokine assay. Data presented here is a summary of 3 different experiments. (D) HCMV-infected MRC-5 cells expressing either wild-type or mutated (to disallow CD8 co-receptor binding) HLA*B3508 were exposed to CPS- or FPT-specific T cells at 2 different responder-to-stimulator ratios, and IFN-γ expression measured using an intracellular cytokine assay. These data are representative of 3 different experiments and shows mean fluorescence intensity (MFI) of IFN-γ expression in CPS- or FPT-specific T cells. (E) MRC-5 cells expressing HLA B*3508 were pre-sensitized with synthetic peptide epitopes (CPS or FPT) and then exposed to CPS- or FPT-specific T cells (responder to stimulator ratio of 2:1). These T cells were assessed for IFN-γ expression as described above. MFI indicates mean fluorescence intensity.