IL13 and glioblastoma: Although GBM cells do not secrete classical drivers of the M1 or M2 phenotypes (IFNγ, TNFα, IL-4, and IL-13), RelB in GBM cells supports expression of known activators and chemoattractants of GAMs, including members of the macrophage inflammatory protein (MIP), colony-stimulating factor (CSF), and the macrophage chemotactic protein (MCP) families50,52.