Among different histological types of brain tumor, astrocytoma (WHO grade II-IV), oligodendrogliomas (WHO grade II-III), ependymomas (WHO grade II-III), and pilocytic astrocytoma (WHO grade I), in which the most malignant GMB (grade IV) belongs to astrocytoma, PD-1 cascade, especially in CD4+ T cells, reflect the severity of the disease is clearly increased in grade III (12.3 ± 0.9%) and IV patients (16.3 ± 0.6%), with the grade IV having the highest value [34]. Here, PDCD1 is linked to astrocytoma (excluding glioblastoma).