CD4 and glioma: Glioma cells secrete different types of chemokines, cytokines and growth factors that enhance infiltration of various cells such as astrocytes, pericytes, endothelial cells, circulating progenitor cells, and a range of immune cells including microglia, peripheral macrophages, myeloid-derived suppressor cells (MDSC), CD4+ T cells as well as Treg cells into the tumor (56–59).