FIGURE 1.

Blockade of CTLA-4 and PD-1 and PD-L1 to enhance antitumor response. (Left) Co-stimulation that CTLA-4 negatively regulates is required for initial activation of CD8 T cell during recognition of its specific tumour antigen, presented by an antigen-presented cell in the lymph node. Blocking CTLA-4 by anti-CTLA-4 antibodies could restore the intensity of co-stimulation. (Right) Activated CD8 T cells migrate to the tumor side based on recognizing specific tumor antigens expressed on the target cancer cell. Once recognized, the antitumor T cell response gets weak, with T cells expressing PD-1 and target cells expressing PD-L1. The negative regulation could be blocked by anti-PD-1 or anti-PD-L1 antibodies.