CTLA4 and neoplasm: Immune-check points, such as CTLA-4 (expressed on activated CTL precursors and that binds B7.1 in the lymph-nodes) and PD-1 (expressed on tumor infiltrating CTLs and which binds PD-L1 and or PD-L2 in the tumor) may, consequently, become opportunistic instruments of the tumor to escape the immuno-surveillance system [96].