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. Author manuscript; available in PMC: 2017 Oct 5.
Published in final edited form as: Nat Rev Endocrinol. 2017 Jan 20;13(4):195–207. doi: 10.1038/nrendo.2016.205

Figure 1.

Figure 1

A. Normal CTLA4 interaction with B7 costimulatory ligand. 1) First activation signal is initiated when T-cell receptor (TCR) binds to antigen presenting cell’s (APC) MHC presenting an antigen. 2) Second activation signal is fired when CD28 receptor binds to B7 costimulatory ligand on the APC. 3) CTLA4 receptors present on T-cell act as a checkpoint, and inhibits T-cell activation by outcompeting CD28 receptors to bind to B7 ligand. This negates the effect of second activation signal. B. Ipilimumab, an anti-CTLA4 antibody, indirectly increases T-cell activity by binding to the CTLA4 receptor. Second activation signal via B7 and CD28 connection is reactivated. C. By blocking either PD-1 or PD-L1 protein, Nivolumab enables the T-cell to detect tumor cells.

D. By blocking either PD-1 or PD-L1 protein, Nivolumab enables the T-cell to detect tumor cells.