GB-derived exosomes have limited ability to activate CD8+ T lymphocytes (Iorgulescu et al., 2016) yet it has been reported that the expression of CD86 on glioma cell lines can be bound competitively by cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), leading to possible T cell immunosuppression (Walker and Sansom, 2011). Here, CTLA4 is linked to central nervous system cancer.