HAVCR2 and glioma: Glioma TME exerts immunosuppression through multiple integrated mechanisms, including the infiltration of immunosuppressive cells such as M2-polarized glioma-associated macrophages (GAMs), Tregs and MDSCs; the secretion of immunosuppressive cytokines like transforming growth factor-beta (TGF-β) and interleukin-10 (IL-10); the paucity of TILs, and the upregulated expression of inhibitory immune checkpoint molecules such as PD-1, T cell immunoglobulin and mucin-domain containing-3 (TIM-3), and lymphocyte activation gene-3 (LAG-3) (139–141).