CTLA4 and cancer: Based on the findings of the previous studies, Allison et al. hypothesized that the transient blockade of CTLA-4 might increase the proliferation and activation of T-cells to a higher level than that which may be allowed and tolerated by the normal physiology, such that the transient blockade of CTLA-4 using an antibody could provide a new strategy for anti-cancer therapy [53,54].