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. Author manuscript; available in PMC: 2022 Sep 1.
Published in final edited form as: Radiol Clin North Am. 2021 Sep;59(5):875–886. doi: 10.1016/j.rcl.2021.05.010

Figure 1.

Figure 1.

Illustration highlighting the interaction between CTLA-4 (on a T cell) and B7 (on an antigen presenting cell or tumor), and interaction between PD-1 (on a T cell) and PD-L1 (on an antigen presenting cell or tumor). Inhibitors of CTLA-4 (for example, ipilimumab) block the interaction between CTLA-4 and B7. Nivolumab and pembrolizumab are examples of immunotherapy agents that block PD-1, preventing the interaction between PD-1 and PD-L1. These inhibitors enhance anti-tumor activity through the aforementioned blockades.

APC = antigen presenting cell, TCR = T cell receptor, MHC = major histocompatibility complex, CD28 interacts with B7 to generate a co-stimulatory signal to T-cells. Yellow “oval” insert between MHC and TCR indicates processed peptide presented by MHC to TCR/T cell.