CD4 and central nervous system cancer: The immune infiltrate in diffuse glioma is highly heterogeneous, and the immune landscape of the glioma tumor microenvironment is predominantly composed of myeloid cells, with lymphocytes being comparatively sparse, including macrophages, microglia, myeloid-derived suppressor cells, lymphocytes (such as CD8+ cytotoxic T cells, CD4+ regulatory T cells, and B cells), natural killer (NK) cells, and neutrophils.