Immunosuppressive cells include tumor-associated microglia and macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), and regulatory B cells (Bregs), while the anti-tumor immune cells include T cells (CD4+ helper T cells, CD8+ cytotoxic T cells) and natural killer (NK) cells, etc. Infiltration or dysfunction of these cells is one of the causes of the highly immunosuppressive and “cold” TME phenotype of the GBM (26). Here, CD4 is linked to glioblastoma.