Moreover, while GITR was highly expressed in GBM Treg cells (~85%), its expression was significantly lower in Treg cells in the spleen (Supplementary Figs. 6c, 7a) and blood (~25%) (Supplementary Fig. 6d) of tumor-bearing mice (~20%), indicating that GITR is relatively selectively expressed in GBM-infiltrating Treg cells. This evidence concerns the gene TNFRSF18 and glioblastoma.