Activated pericytes have been reported to present properties of myeloid cells, such as macrophages, expressing macrophage markers and acquiring phagocytic activity and the ability to present antigens to T cells [17, 18, 34]. To identify if pericytes might gain some of the immunosuppressive properties of TAMs in response to their interaction with GBM cells, we first analyzed the expression of several membrane molecules implicated in the inhibition of anti-tumor responses [24, 35]. Interestingly, we found high levels of Il4ra and Il1rn mRNA expression in pericytes, after 24 hours following interaction with GBM cells (Figure 2A). Then we determined if the immunosuppressive ligand of PD-1, PDL-1, which has been associated with glioblastoma progression [3, 36, 37], was expressed in pericytes, and if its levels changed in response to GBM interaction. We observed that PDL-1 was expressed in pericytes in resting conditions, but its level of expression was maintained upon GBM cell interaction (Figure 2B). Interestingly, we found that expression of the co-stimulatory molecules CD80 and CD86 was significantly reduced in GBC-PC compared to control pericytes (Figure 2C). To analyze if the ability of brain pericytes to present antigen to T cells might be affected by GBM cell interaction, we determined the expression levels of major histocompatibility complex class II molecules (MHC-II) in GBC-PC. We found a drastic and significant reduction of MHC-II expression in pericytes when cocultured with GBM cells compared to control pericytes (Figure 2D). None of these markers was detected in control GBM cells. These data support an immunomodulatory phenotype in pericytes in response to GBM cell interaction.