Expansion of Antigen-specific CD8+ T Cells

PBMCs (3–5 × 10⁶) were used to expand antigen-specific CD8⁺ T cells^{24 (link)–26 (link)}. Briefly, PBMCs were thawed in RF10 supplemented with 2 µg/ml deoxyribonuclease I (DNase; Sigma-Aldrich) and washed in serum-free RPMI. One third of PBMCs were pulsed for 1 h with IBV peptide pools (7 peptide pools ranging between 8 and 22 peptides per pool; Supplementary Table 1) in serum-free RPMI at 10 µM at 37*C. Pulsed cells were washed twice with serum-free RPMI, resuspended in RF10 and mixed with the remaining autologous PBMCs (also resuspended in RF10). Cultures were incubated at 37 °C/5% CO₂ for 10–12 days. IL-2 (Roche Diagnostics) was added on day 4 to a final concentration of 20 U/ml.