[Antitumor immune response: what are the roles for gliomas?]

Major advances achieved in immunology along the last decade have considerably improved our appraisal of the interactions between tumor cells and cells of the immune system (including lymphocytes), leading to the current development of immunotherapies as a new treatment strategy against cancer. Due to their localization in the brain, glioma are usually considered to arise in an immunoprivileged site, precluding immune intervention. Recent data challenge such a nihilism. Indeed, glioma infiltrating lymphocytes include T cell clonal expansions, suggesting a response against glioma antigens not yet identified. Furthermore, there is now cumulative evidence that activated T cells can traffic through the central nervous system and that T cells primed by astrocytoma cells in the periphery can recirculate and reach the brain to mediate their anti-tumor effects. Finally, multiple mechanisms by which glioma evade the immune response have been elucidated. However, there are still important enigmas, such as the nature of glioma antigens and the steps of antigen presentation in the brain. Responding to these crucial questions should facilitate the development of immunotherapies against brain tumors, avoiding deleterious auto-immune reactions.