PDCD1 and neoplasm: Our PD-1 DIFFL reconstruction (Figure 2), when combined with the mathematical modeling (Figures 5, 7), suggests that it is the loss of Ag dose-dependent adaptation of the expression of PD-1 receptors in the anti-tumor CD8+ T cells that could be one of major factors resulting in the multiple effects in the presence of acute non-oncogenic infection (1).