CTLA4 and neoplasm: Although tTregs can be recruited into tumors to suppress the effective T cells, most tumor-infiltrating Tregs are iTregs, which can be induced by interleukin (IL)-2 and transforming growth factor beta (TGF-β) and express forkhead box P3 (Foxp3) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) (6).