Single-cell transcriptomics reveal that PD-1 mediates immune tolerance by regulating proliferation of regulatory T cells

• Published in: Genome medicine Vol. 10; no. 1; p. 71
• Main Authors: Leung, Cherry S, Yang, Kevin Y, Li, Xisheng, Chan, Vicken W, Ku, Manching, Waldmann, Herman, Hori, Shohei, Tsang, Jason C H, Lo, Yuk Ming Dennis, Lui, Kathy O
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 20.09.2018; BioMed Central; BMC
• Subjects: Animals; Antigens; Cancer; CD4 antigen; CD4+ regulatory T cells; CD4-Positive T-Lymphocytes - immunology; Cell Count; Cell Line; Cell proliferation; Cell Proliferation - genetics; Cell Survival; Clinical trials; Diabetes; Embryonic stem cells; Embryonic Stem Cells - cytology; Embryonic Stem Cells - metabolism; Foxp3 protein; Gene Expression Profiling; Genome; Genomes; Graft rejection; Graft Rejection - immunology; Human pancreatic beta cells; Humans; Immune system; Immune Tolerance - genetics; Immunological tolerance; Immunoregulation; Immunosuppression; Immunotherapy; Insulin; Islets of Langerhans - cytology; Islets of Langerhans Transplantation; Lymphocytes; Lymphocytes T; Mice, Inbred C57BL; Pancreas; Pancreatic beta cells; PD-1; PD-1 protein; Programmed Cell Death 1 Receptor - metabolism; Ribonucleic acid; RNA; Signal Transduction; Single-Cell Analysis; Single-cell transcriptomics; Spleen - cytology; Stem cells; T cell receptors; T-Lymphocytes, Regulatory - immunology; Transplant tolerance; Ubiquitin; Single-cell transcriptomics; Transplant tolerance; PD-1; CD4+ regulatory T cells; Human pancreatic beta cells
• ISSN: 1756-994X; 1756-994X
• DOI: 10.1186/s13073-018-0581-y

We have previously reported an antigen-specific protocol to induce transplant tolerance and linked suppression to human embryonic stem cell (hESC)-derived tissues in immunocompetent mice through coreceptor and costimulation blockade. However, the exact mechanisms of acquired immune tolerance in this model have remained unclear. We utilize the NOD.Foxp3 reporter mouse line and an ablative anti-hCD2 antibody to ask if CD4 FOXP3 regulatory T cells (Treg) are required for coreceptor and costimulation blockade-induced immune tolerance. We also perform genome-wide single-cell RNA-sequencing to interrogate Treg during immune rejection and tolerance and to indicate possible mechanisms involved in sustaining Treg function. We show that Treg are indispensable for tolerance induced by coreceptor and costimulation blockade as depletion of which with an anti-hCD2 antibody resulted in rejection of hESC-derived pancreatic islets in NOD.Foxp3 mice. Single-cell transcriptomic profiling of 12,964 intragraft CD4 T cells derived from rejecting and tolerated grafts reveals that Treg are heterogeneous and functionally distinct in the two outcomes of transplant rejection and tolerance. Treg appear to mainly promote chemotactic and ubiquitin-dependent protein catabolism during transplant rejection while seeming to harness proliferative and immunosuppressive function during tolerance. We also demonstrate that this form of acquired transplant tolerance is associated with increased proliferation and PD-1 expression by Treg. Blocking PD-1 signaling with a neutralizing anti-PD-1 antibody leads to reduced Treg proliferation and graft rejection. Our results suggest that short-term coreceptor and costimulation blockade mediates immune tolerance to hESC-derived pancreatic islets by promoting Treg proliferation through engagement of PD-1. Our findings could give new insights into clinical development of hESC-derived pancreatic tissues, combined with immunotherapies that expand intragraft Treg, as a potentially sustainable alternative treatment for T1D.