In fact, while we show the blockade of the PD-1 pathway did lead to GBM rejection (Fig. 4B), this protection was not absolute, indicating that effects of PD-1 blockade monotherapy may not completely restore the anti-tumor function of exhausted T cells, possibly because other immune checkpoint signals and epigenetic factors are also operative2,4,5,33,44,49. Here, PDCD1 is linked to glioblastoma.