The density of tumor-reactive CD137+ PD-1+ CD8+ T cells [24–26] and memory-phenotype CD44hi PD-1+ CD8+ T cells [27, 28] was significantly higher in mH/αCD4-treated mice than αCD4-treated mice (p = 0.03 and p = 0.04) (Fig. 2d-g). This evidence concerns the gene PDCD1 and neoplasm.