CD8+ TEM cells specific to apoptotic epitopes are activated by apoptotic epitopes naturally processed and cross-presented by DCs.
(A) One representative of five experiments in which PBMCs from one patient with acute HCV infection were double-stained with mAb to CD8 and pentamers complexed with the indicated apoptotic epitope, and cultured with autologous DCs that had been pulsed or not with the relevant soluble peptide, apoptotic cloned T cells (ACs = apoptotic cells), ACs previously treated with a negative caspase control (K = Z-FA-FMK), or ACs previously treated with the caspase 3 inhibitor (C3I = z-devd-fmk). After 6 h, CD8+pentamer+ cells were tested for their capacity to produce the different cytokines indicated by the ICS assay. Counterplots are gated on CD8+pentamer+ cells and show percentages of the different cytokine-producing cells in each quadrant. (B) Cumulative experiments in 5 independent patients, performed as described in (A), showing the percentages of cells producing the indicated cytokines in CD8+pentamer+ cells in response to the following stimuli: autologous DCs alone (a); DCs that had been pulsed with the MYH9741–749 peptide (b); DCs that had been pulsed with ACs, previously treated with a negative caspase control (Z-FA-FMK) (c); or DCs that had been pulsed with ACs previously treated with the caspase 3 inhibitor (Z-DEVD-FMK) (d). Each symbol represents a single patient. (C) Correlation (analysed at the 15th month after clinical onset) between the percentage of CD8+pentamer+ cells specific to apoptotic epitopes and the percentage of circulating apoptotic T cells in patients with acute HCV infection experiencing chronic infection (filled circles) or infection resolution (empty circles). Statistical analysis was performed using non-parametric Spearman's test.