Although we did verify a decreased level of glioma-resident Treg in the GFAP:(12)V-Ha-Ras transgenic glioma model (Shannon et al., 2005) that was backcrossed to a globally IDO−/− background, this did not distinguish the contribution of glioma-expressed- and peripherally expressed-IDO to CNS-resident Treg. The gene discussed is IDO1; the disease is central nervous system cancer.