Fig 2.

Ligand–receptor interactions between tumour cells and activated T cells and targets for anti-PD-1 and anti-CTLA-4 therapy. (a) The interaction of the CTLA-4 receptor on T cells with the CD-80 ligand (B-7 homologue) on an antigen-presenting cells promotes tumour escape. The binding of an anti-CTLA-4 antibody promotes T-cell activation and elimination of tumour cells. (b) The interaction of PD-1 receptor on T cells with PD-L1 ligand on tumour cells promotes T-cell anergy and tumour escape. In the presence of an anti-PD-1 or anti-PD-L1 antibody, T cells become activated and initiate tumour cell death. CTL-4, T-lymphocyte-associated antigen 4; PD-1, programmed cell death 1; APC, antigen-presenting cells; MHC, major histocompatibility complex; TCR, T-cell receptor. From ‘CTLA-4 and PD-1 pathways: similarities, differences, and implications of their inhibition’, E. Buchbinder and A. Desai, American Journal of Clinical Oncology, 2016; 39: 98–106. Reprinted with permission.