As the most important component of the immune response in the tumor microenvironment of most solid tumors, tumor-infiltrating lymphocytes (TILs), represented by CD4+ Th, CD8+ CTLs, and CD4+/CD25+/FoxP3+ T reg (23–26), are only present in remarkably low numbers in the CNS compared to other tumor types. This evidence concerns the gene CD8A and neoplasm.