Nevertheless, a substantial part of CD8 T cells display a PD-1+, LAG-3+, TIGIT+, CD39+, KLRG1−, and CD57− profile, indicative of T cell exhaustion [37,60] and suggestive that factors in the glioblastoma micro-environment negatively control an anti-tumor CD8 T-cell response. Here, PDCD1 is linked to glioblastoma.