Engagement of the PD-1 immunoinhibitory receptor by a novel B7 family member leads to negative regulation of lymphocyte activation

GJ Freeman, AJ Long, Y Iwai, K Bourque… - The Journal of …, 2000 - rupress.org
GJ Freeman, AJ Long, Y Iwai, K Bourque, T Chernova, H Nishimura, LJ Fitz, N Malenkovich…
The Journal of experimental medicine, 2000rupress.org
PD-1 is an immunoinhibitory receptor expressed by activated T cells, B cells, and myeloid
cells. Mice deficient in PD-1 exhibit a breakdown of peripheral tolerance and demonstrate
multiple autoimmune features. We report here that the ligand of PD-1 (PD-L1) is a member
of the B7 gene family. Engagement of PD-1 by PD-L1 leads to the inhibition of T cell receptor–
mediated lymphocyte proliferation and cytokine secretion. In addition, PD-1 signaling can
inhibit at least suboptimal levels of CD28-mediated costimulation. PD-L1 is expressed by …
PD-1 is an immunoinhibitory receptor expressed by activated T cells, B cells, and myeloid cells. Mice deficient in PD-1 exhibit a breakdown of peripheral tolerance and demonstrate multiple autoimmune features. We report here that the ligand of PD-1 (PD-L1) is a member of the B7 gene family. Engagement of PD-1 by PD-L1 leads to the inhibition of T cell receptor–mediated lymphocyte proliferation and cytokine secretion. In addition, PD-1 signaling can inhibit at least suboptimal levels of CD28-mediated costimulation. PD-L1 is expressed by antigen-presenting cells, including human peripheral blood monocytes stimulated with interferon γ, and activated human and murine dendritic cells. In addition, PD-L1 is expressed in nonlymphoid tissues such as heart and lung. The relative levels of inhibitory PD-L1 and costimulatory B7-1/B7-2 signals on antigen-presenting cells may determine the extent of T cell activation and consequently the threshold between tolerance and autoimmunity. PD-L1 expression on nonlymphoid tissues and its potential interaction with PD-1 may subsequently determine the extent of immune responses at sites of inflammation.
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