CD86 and glioma: As early as the 1920s, it was discovered that microglia could engulf glioma cells.47 Microglia can also respond to stimulation of the TME, be activated to transform into an amoeboid shape, and express major histocompatibility complex (MHC) class I (MHC-I) and MHC-II, as well as co-stimulatory molecules such as CD86, functioning as APCs to activate T cells.48 However, the glioma environment can induce microglia to transition into a pro-tumor phenotype.