To better understand the role of IDO in brain tumors under normal conditions, we have now created a transgenic model of glioma that is selectively deficient for IDO only in cells capable of forming astrocytoma by backcrossing a tamoxifen-induced GFAP-Cre driven high grade astrocytoma mouse model (Chow et al., 2011) with floxed IDO mice. The gene discussed is IDO1; the disease is astrocytoma (excluding glioblastoma).