title: No evidence for dualism in function and receptors: PD-L2/B7-DC is an inhibitory regulator of human T cell activation.
abstract: The B7 family member programmed-death-1-ligand 2 (PD-L2/B7-DC) is a ligand for programmed-death-receptor 1 (PD-1), a receptor involved in negative regulation of T cell activation. Several independent studies have reported that PD-L2, however, can also potently costimulate murine T cells via an additional yet unidentified receptor. In this study, we evaluated the contribution of PD-L2 to the activation of human T cells using a novel system of engineered T cell stimulators that expresses membrane-bound anti-CD3 antibodies. Analyzing early activation markers, cytokine production and proliferation, we found PD-L2 to consistently inhibit T cell activation. PD-L2 inhibition affected CD4+ and CD8+ T cells and was not abrogated by costimulation via CD28. Blocking PD-1 reverted the inhibitory effect of PD-L2, demonstrating involvement of this pathway. In human T cells, we found no evidence for any of the costimulatory effects described for PD-L2 in murine systems. In line with our functional data that do not point to stimulatory PD-L2-ligands, we show that binding of PD-L2-immunoglobulin to activated human T cells is abrogated by PD-1 antibodies. Our results demonstrate that PD-L2 negatively regulates human T cell activation and thus might be a candidate molecule for immunotherapeutic approaches aimed to attenuate pathological immune responses.
authors.affiliation: Institute of Immunology, Center for Hygiene and Medical Microbiology, Medical University of Vienna, Vienna, Austria.
authors.forename: Katharina
authors.initials: K
authors.lastname: Pfistershammer
authors.forename: Christoph
authors.initials: C
authors.lastname: Klauser
authors.forename: Winfried F
authors.initials: WF
authors.lastname: Pickl
authors.forename: Johannes
authors.initials: J
authors.lastname: Stöckl
authors.forename: Judith
authors.initials: J
authors.lastname: Leitner
authors.forename: Gerhard
authors.initials: G
authors.lastname: Zlabinger
authors.forename: Otto
authors.initials: O
authors.lastname: Majdic
authors.forename: Peter
authors.initials: P
authors.lastname: Steinberger
mesh_terms: D015703:Antigens, CD; D000954:Antigens, Surface / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000502:physiology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008213:Lymphocyte Activation; D010455:Peptides / Q000502:physiology*; D061027:Programmed Cell Death 1 Ligand 2 Protein; D061026:Programmed Cell Death 1 Receptor; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D000954:Antigens, Surface; D051017:Apoptosis Regulatory Proteins; D016207:Cytokines; D036341:Intercellular Signaling Peptides and Proteins; C105992:PDCD1 protein, human; C556977:PDCD1LG2 protein, human; D010455:Peptides; D061027:Programmed Cell Death 1 Ligand 2 Protein; D061026:Programmed Cell Death 1 Receptor