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. Author manuscript; available in PMC: 2016 Mar 4.
Published in final edited form as: Expert Opin Biol Ther. 2015 Jun 3;15(8):1191–1203. doi: 10.1517/14712598.2015.1051028

Figure 1.

Figure 1

A diagram demonstrating interactions between PD-1 receptor expressed on immune cells and PD-L1. A PDL-1 expressing antigen-presenting cell delivers a negative signal to the PD-1 receptor expressed on immune cells, which blocks their effector functions. In T-cells, Ag-specific responses are blocked. In NK cells, the ability to mediate cytotoxicity is decreased. In B cells, the Ab production is inhibited. In contrast, the same negative signal enhances the development and suppressor functions of Treg. Checkpoint receptor engagement directly blocks functions of immune cells and also has indirect suppressive effects mediated by Treg.

NK: Natural killer; PD-1: Programmed death-1; PDL-1: Programmed death ligand-1; TCR: T-cell receptor.