Tolerance induced by apoptotic antigen-coupled leukocytes is induced by PD-L1+ and IL-10-producing splenic macrophages and maintained by T regulatory cells

• Published in: The Journal of immunology (1950) Vol. 187; no. 5; pp. 2405 - 2417
• Main Authors: Getts, Daniel R, Turley, Danielle M, Smith, Cassandra E, Harp, Christopher T, McCarthy, Derrick, Feeney, Emma M, Getts, Meghann Teague, Martin, Aaron J, Luo, Xunrong, Terry, Rachael L, King, Nicholas J C, Miller, Stephen D
• Format: Journal Article
• Language: English
• Published: United States 01.09.2011
• Subjects: Animals; Antigens - immunology; Apoptosis - immunology; B7-1 Antigen - biosynthesis; B7-1 Antigen - immunology; B7-H1 Antigen; Cell Separation; Encephalomyelitis, Autoimmune, Experimental - immunology; Enzyme-Linked Immunosorbent Assay; Female; Flow Cytometry; Immune Tolerance - immunology; Immunohistochemistry; Interleukin-10 - biosynthesis; Interleukin-10 - immunology; Lymphocyte Activation - immunology; Lymphocytes - immunology; Macrophage Activation - immunology; Macrophages - immunology; Macrophages - metabolism; Membrane Glycoproteins - biosynthesis; Membrane Glycoproteins - immunology; Mice; Mice, Inbred C57BL; Myelin Proteolipid Protein - immunology; Peptide Fragments - immunology; Peptides - immunology; Spleen - cytology; Spleen - immunology; T-Lymphocytes, Regulatory - immunology
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.1004175

Ag-specific tolerance is a highly desired therapy for immune-mediated diseases. Intravenous infusion of protein/peptide Ags linked to syngeneic splenic leukocytes with ethylene carbodiimide (Ag-coupled splenocytes [Ag-SP]) has been demonstrated to be a highly efficient method for inducing peripheral, Ag-specific T cell tolerance for treatment of autoimmune disease. However, little is understood about the mechanisms underlying this therapy. In this study, we show that apoptotic Ag-SP accumulate in the splenic marginal zone, where their uptake by F4/80(+) macrophages induces production of IL-10, which upregulates the expression of the immunomodulatory costimulatory molecule PD-L1 that is essential for Ag-SP tolerance induction. Ag-SP infusion also induces T regulatory cells that are dispensable for tolerance induction but required for long-term tolerance maintenance. Collectively, these results indicate that Ag-SP tolerance recapitulates how tolerance is normally maintained in the hematopoietic compartment and highlight the interplay between the innate and adaptive immune systems in the induction of Ag-SP tolerance. To our knowledge, we show for the first time that tolerance results from the synergistic effects of two distinct mechanisms, PD-L1-dependent T cell-intrinsic unresponsiveness and the activation of T regulatory cells. These findings are particularly relevant as this tolerance protocol is currently being tested in a Phase I/IIa clinical trial in new-onset relapsing-remitting multiple sclerosis.