Uptake of apoptotic cells (ACs) by dendritic cells (DCs) and induction of a tolerogenic DC phenotype is an important mechanism for establishing peripheral tolerance to self-antigens. The receptors involved and underlying signaling pathways are not fully understood. Here, we identify Dectin-1 as a crucial tolerogenic receptor binding with nanomolar affinity to the core domain of several annexins (annexin A1, A5, and A13) exposed on ACs. Annexins bind to Dectin-1 on a site distinct from the interaction site of pathogen-derived β-glucans. Subsequent tolerogenic signaling induces selective phosphorylation of spleen tyrosine kinase (SYK), causing activation of NADPH oxidase-2 and moderate production of reactive oxygen species. Thus, mice deficient for Dectin-1 develop autoimmune pathologies (autoantibodies and splenomegaly) and generate stronger immune responses (cytotoxic T cells) against ACs. Our data describe an important immunological checkpoint system and provide a link between immunosuppressive signals of ACs and maintenance of peripheral immune tolerance.
Keywords: Dectin-1; NOX-2; SYK; annexin (A1, A5, and A13); apoptotic cells; autoimmunity; biased agonism; dendritic cells; peripheral immune tolerance; reactive oxygen species.
Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.