IDO1 and glioblastoma: Several experimental antibodies against CTLA-4, indoleamine-pyrrole 2,3-dioxygenase (IDO), and PDL-1 have been tested, both in monotherapy and combination, in mouse models of glioblastoma, showing an improvement in long-term survival associated with an increase in T-cell count and proliferation and a reduction of tumor recurrence in long-term surviving mice, suggesting a role for tumor-directed immune memory [78].