Susceptibility of virus-specific CD8⁺ T cells to apoptosis.

PBMCs were isolated from donors with AIM and were cultured in the absence of exogenous mediators (A). Total viable cell recovery was measured at various times after culture. In addition, the percentage of total CD8⁺ T cells or virus-specific (RAK lytic epitope) CD8⁺ T cells was also determined in the cultured PBMC populations. This enabled the absolute number of total CD8⁺T cells and EBV-specific CD8⁺ T cells to be determined after culture. Survival of the cells after culture was expressed as a percentage of the original number of cells at day 0. Survival of total CD8⁺ and EBV-specific CD8⁺ T cells in culture was also determined in patients who had recovered from AIM (B). We also measured the absolute number of CD45RA⁺ or CD45RA⁻ virus-specific CD8⁺ T cells at different times after culture by multiplying the percentages of these cells that were present at different times by the cell recovery (C). The percentage survival of CD45RA⁺ or CD45RA⁻EBV-specific CD8⁺ T cells was determined relative to the initial input at day 0. Results shown in panels A and B are the mean and SEM of triplicate determinations for the survival of cells from 1 individual each and are representative of at least 4 separate experiments that have been performed in each case. In panel C, the relative survival of EBV-specific CD8⁺ T cells that do or do not re-express CD45RA in 5 patients tested are shown.