CTLA4 and neoplasm: Single-cell sequencing has found the expression of some characteristic markers in Tregs, including TIGIT, CTLA4, FOXP3, TNFRSF18, LAYN, DUSP4, FANK1 and LAIR2. Among them, TIGIT expressed by Tregs can interact with nectins (especially nectin4) expressed by tumor cells [19, 56, 57].