Fig. 5

The mechanism and usage of immune checkpoint inhibitors. PD-1/PD-L1 binding inhibits T cell killing of lymphoma cells. Blocking PD-1 and PD-L1 allows T cell killing, APC-T cell interaction, and T cell stimulation in a lymphoma microenvironment (a). When SIRPα interacts with its ligand CD47 on tumor cells, SIRPα undergoes tyrosine phosphorylation and recruits the protein tyrosine phosphatases. These phosphatases inhibit the ability of prophagocytic receptors to trigger phagocytosis when ligands are present on tumor cells. Blocking CD47-SIRPα signaling with an anti-CD47 or SIRPα monoclonal antibody enhances macrophage-mediated phagocytosis of lymphoma cells (b). Anti-CD47 monoclonal antibody synergises with Rituximab when lymphoma cells double express CD20 and CD47 proteins (c)