Focus on TILs: Prognostic significance of tumor infiltrating lymphocytes in human glioma.

Significant work in animal models combined with compelling studies in human patients together have begun to provide a higher resolution picture of how the immune system regulates cancer development. Currently, this immune system-tumor interaction is represented by the concept of cancer immunoediting, which emphasizes that immunity may subserve either classical cancer immunosurveillance functions or promote the eventual outgrowth of immunoevasive cancer cells. One important line of evidence supporting an immunosurveillance process in humans has been the finding that the presence of distinct profiles of TILs may be correlated with improved clinical outcomes in a subset of human cancers. However, the contribution of TILs to the natural history of gliomas is less clear. Moreover, understanding the relationship between TILs and cancers of the brain is particularly challenging because our understanding of how immune responses develop in the central nervous systems is still evolving. In this review, we will first provide an overview of three important themes in the central nervous system anti-tumor immunity--i.e., antigen expression, how antigen may be presented, and lymphocyte trafficking--and subsequently discuss the extant work on TILs in glioma.