Fig. 2
From: Targeting immune checkpoints in hematological malignancies
PD-1-mediated immune regulation. Under low expression levels of PD-L1, CD80 restricts PD-L1 function by forming the PD-L1/CD80 cis-heterodimer. The PD-L1/CD80 cis-heterodimer prevents the PD-1/PD-L1 trans-interaction, whereas the ability to bind to the CD28 co-stimulatory receptor is retained (left). Upregulation of PD-L1 on APCs allows the PDL-1/PD-1 trans-interaction, leading to SHP2-dependent negative regulation of the CD28 signaling pathway as well as transcriptional repression of TCR-induced effector genes (right)