Volume 45, Issue 4, Pages 468-472 (October 2006) Turning on the off switch: Regulation of anti-viral T cell responses in the liver by the PD- 1/PD-L1 pathway  Arash Grakoui, E. John Wherry, Holly L. Hanson, Christopher Walker, Rafi Ahmed  Journal of Hepatology  Volume 45, Issue 4, Pages 468-472 (October 2006) DOI: 10.1016/j.jhep.2006.07.009 Copyright © 2006 European Association for the Study of the Liver Terms and Conditions

Fig. 1 Achieving T cell balance. Pathogen-specific CD8+ T cells are “turned on” through interaction of their TCR with MHC I presenting antigen in the presence of appropriate costimulation. These same T cells may be “turned off” through the interaction of PD-1 on their cell surface and PD-L1 expressed on hepatocytes and liver-resident parenchymal cells. Journal of Hepatology 2006 45, 468-472DOI: (10.1016/j.jhep.2006.07.009) Copyright © 2006 European Association for the Study of the Liver Terms and Conditions

Fig. 2 T cell activation and proliferation require positive signaling through the TCR receptor complex. The interaction of PD-1 with PD-L1 leads to phosphorylation of the ITSM domain of PD-1, recruitment of SHP-2, and cell cycle arrest. Journal of Hepatology 2006 45, 468-472DOI: (10.1016/j.jhep.2006.07.009) Copyright © 2006 European Association for the Study of the Liver Terms and Conditions