title: Influence of PD-L1 cross-linking on cell death in PD-L1-expressing cell lines and bovine lymphocytes.
abstract: Programmed death-ligand 1 (PD-L1) blockade is accepted as a novel strategy for the reactivation of exhausted T cells that express programmed death-1 (PD-1). However, the mechanism of PD-L1-mediated inhibitory signalling after PD-L1 cross-linking by anti-PD-L1 monoclonal antibody (mAb) or PD-1-immunogloblin fusion protein (PD-1-Ig) is still unknown, although it may induce cell death of PD-L1(+) cells required for regular immune reactions. In this study, PD-1-Ig or anti-PD-L1 mAb treatment was tested in cell lines that expressed PD-L1 and bovine lymphocytes to investigate whether the treatment induces immune reactivation or PD-L1-mediated cell death. PD-L1 cross-linking by PD-1-Ig or anti-PD-L1 mAb primarily increased the number of dead cells in PD-L1(high) cells, but not in PD-L1(low) cells; these cells were prepared from Cos-7 cells in which bovine PD-L1 expression was induced by transfection. The PD-L1-mediated cell death also occurred in Cos-7 and HeLa cells transfected with vectors only encoding the extracellular region of PD-L1. In bovine lymphocytes, the anti-PD-L1 mAb treatment up-regulated interferon-γ (IFN-γ) production, whereas PD-1-Ig treatment decreased this cytokine production and cell proliferation. The IFN-γ production in B-cell-depleted peripheral blood mononuclear cells was not reduced by PD-1-Ig treatment and the percentages of dead cells in PD-L1(+) B cells were increased by PD-1-Ig treatment, indicating that PD-1-Ig-induced immunosuppression in bovine lymphocytes could be caused by PD-L1-mediated B-cell death. This study provides novel information for the understanding of signalling through PD-L1.
authors.affiliation: Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Ryoyo
authors.initials: R
authors.lastname: Ikebuchi
authors.forename: Satoru
authors.initials: S
authors.lastname: Konnai
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Okagawa
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Yokoyama
authors.forename: Chie
authors.initials: C
authors.lastname: Nakajima
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Shiro
authors.initials: S
authors.lastname: Murata
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ohashi
mesh_terms: D000818:Animals; D058846:Antibodies, Monoclonal, Murine-Derived / Q000494:pharmacology*; D001402:B-Lymphocytes / Q000276:immunology*; D060890:B7-H1 Antigen / Q000235:genetics / Q000276:immunology*; D016466:CHO Cells; D019556:COS Cells; D002417:Cattle; D016923:Cell Death / Q000187:drug effects / Q000276:immunology; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003412:Cricetulus; D006367:HeLa Cells; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects*; D007152:Immunologic Capping / Q000187:drug effects*; D007371:Interferon-gamma / Q000276:immunology
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D060890:B7-H1 Antigen; D007371:Interferon-gamma
keywords: bovine immunology; cell death; immunoglobulin fusion protein; programmed death-ligand 1