CTLA4 and neoplasm: The mechanism of inhibition of anti-tumour effector T cells by Treg involves several molecular pathways: 1) Tregs may inhibit proliferation and cytokine secretion of T effector cells by IL-10, adenosine production from CD39 on its surface and IL-35, which can be reversed by adding neutralising antibodies (132, 133); 2) via the PD-1/PD-L1 pathway to suppress anti-tumoral immunity in HCC (134); and also via 3) the co-inhibitory molecule CTLA-4 (135).