We think that the inefficiency of CD8 is based on three arguments: first, the inverse relationship between CD8 cell tissue concentration and survival may reflect an inefficient or blocked cell; secondly, the strong correlation between CD8 and immunosuppressive mechanisms in the sense of higher CD8 density supports the argument that CD8 cells could be blocked by CD163 positive macrophages and the PD1/PDL1 axis; and thirdly, according to the literature, it has been reported that T cell exhaustion is a major contributor to the failure of T cells in GBM [49]. Here, PDCD1 is linked to glioblastoma.