@article {542411,
	title = {PD-1 and its ligands in tolerance and immunity.},
	journal = {Annu Rev Immunol},
	volume = {26},
	year = {2008},
	month = {2008},
	pages = {677-704},
	abstract = {Programmed death 1 (PD-1) and its ligands, PD-L1 and PD-L2, deliver inhibitory signals that regulate the balance between T cell activation, tolerance, and immunopathology. Immune responses to foreign and self-antigens require specific and balanced responses to clear pathogens and tumors and yet maintain tolerance. Induction and maintenance of T cell tolerance requires PD-1, and its ligand PD-L1 on nonhematopoietic cells can limit effector T cell responses and protect tissues from immune-mediated tissue damage. The PD-1:PD-L pathway also has been usurped by microorganisms and tumors to attenuate antimicrobial or tumor immunity and facilitate chronic infection and tumor survival. The identification of B7-1 as an additional binding partner for PD-L1, together with the discovery of an inhibitory bidirectional interaction between PD-L1 and B7-1, reveals new ways the B7:CD28 family regulates T cell activation and tolerance. In this review, we discuss current understanding of the immunoregulatory functions of PD-1 and its ligands and their therapeutic potential.},
	keywords = {Animals, Antigens, CD, Antigens, CD274, Antigens, CD80, Apoptosis Regulatory Proteins, Humans, Immunity, Ligands, Models, Immunological, Programmed Cell Death 1 Receptor, Self Tolerance},
	issn = {0732-0582},
	doi = {10.1146/annurev.immunol.26.021607.090331},
	author = {Keir, Mary E and Butte, Manish J and Freeman, Gordon J and Sharpe, Arlene H}
}
