ICAM1 and neoplasm: To assess if this cytolytic activity of endogenous CTLs triggered by the elimination of Tregs requires the presence of ICAM-1 on E0771 tumor cells, we implanted primary E0771 tumors in syngeneic FOXP3-DTR-GFP mice that express a diphtheria toxin receptor selectively on FOXP3-positive Treg cells (50) and used a DTx to effectively deplete Tregs from the tumor-implanted mice (Figures 2A, , B).