Our study indicated that the human T cells in the brain of HIS-DRAGA mice are functional and secrete human pro-inflammatory cytokines upon stimulation, thus providing a rational ground for using these mice to investigate the role of brain-resident T cells during infections, neuroinflammation and targets for cancer PD-1 therapy as recently described (Srivastava et al., 2023). This evidence concerns the gene PDCD1 and cancer.