PDCD1 and neoplasm: We isolated CD8+ (Figure 4A) and CD8+PD-1+ T cells (Figure 4B) from patient PBMCs; expanded them in vitro for 15 days with IL-2, anti-CD3 stimulation, and irradiated feeders; and tested their ability to recognize autologous tumor cell lines by IFN-γ-ELISPOT using HLA-A2+ tumor cell lines as target cells.