Fig. 1

Schematic representation of immune co-stimulatory and co-inhibitory molecule receptors on T-cells and their ligands among T cells, antigen-presenting cells and tumor cells, and targeting strategies and agents of immune checkpoint blockade therapy. T-cell activation or inhibition induced by different co-stimulatory or co-inhibitory receptors (which are expressed on T-cells) bind to their ligands (which are expressed on dendritic cells or tumor cells). BTLA B- and T-lymphocyte attenuator, CTLA-4 cytotoxic T-lymphocyte-associated protein 4, HVEM herpes virus entry mediator, MHC major histocompatibility complex, PD-1 programmed cell death 1, PD-L1 programmed cell death ligand-1