IL4 and neoplasm: Interestingly, when we added one of the ligands that were over-expressed in the pericyte-deprived PVN, GAS6, to primary cultures of mouse bone marrow-derived macrophages, we found GAS6 to reinforce IL4-induced alternative activation, indicating that GAS6 signaling may contribute to further polarization of macrophages that have already been primed in a tumor-supportive way (Fig. S8B).