CD3+ and CD8+ T-cell infiltration in GBM’s TME increases from low-grade to high-grade tumors, maybe due to the disruption of the BBB, and at the same time it has been correlated to better patients’ prognosis, independently from age, MGMT promoter methylation, and post-operative treatment [44,46]. The gene discussed is CD8A; the disease is glioblastoma.