Supporting our in vitro results, we have also seen the establishment of inhibitory interactions PD-1/PDL-1 between lymphocytes and pericytes, respectively, in perivascular areas. Interestingly, we don’t detect either the presence of grafted pericytes in grafts of control mice, or when pericytes are grafted with glioblastoma cells without being previously co-cultured. As it was expected, these last control mice showed the same tumor progression that control mice grafted with glioblastoma alone. However, we observe pericytes in grafted GBM+Pc mice, indicating they need to be conditioned by interaction with Glioblastoma previously to anchor in perivascular areas. This effect may be due to a decreased competence of grafted versus host pericytes for trophic factors to survive; and suggests that GBM cells confer increasing competence to grafted pericytes, as well as inducing immunotolerance, which in addition could facilitate the cell anchorage to perivascular areas.