Clearance of apoptotic cells is critical for control of tissue homeostasis however the full range of receptor(s) on phagocytes responsible for recognition of apoptotic cells remains to be identified. Here we show that dendritic cells (DCs), macrophages and endothelial cells use scavenger receptor type F family member 1 (SCARF1) to recognize and engulf apoptotic cells via C1q. Loss of SCARF1 impairs uptake of apoptotic cells. Consequently, in SCARF1-deficient mice, dying cells accumulate in tissues leading to a lupus-like disease with the spontaneous generation of autoantibodies to DNA-containing antigens, immune cell activation, dermatitis and nephritis. The discovery of SCARF1 interactions with C1q and apoptotic cells provides insights into molecular mechanisms involved in maintenance of tolerance and prevention of autoimmune disease.Clearance of apoptotic cells is one of the most important processes of the immune system and is necessary for the homeostatic maintenance of healthy tissues and removal of infected or damaged cells [1][2][3] . Several types of cells are capable of apoptotic cell uptake, including Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use: http://www.nature.com/authors/editorial_policies/license.html#terms * Correspondence and requests for materials should be addressed to: T.K. M. means.terry@mgh.harvard.edu, 617-726-6497). Note: Supplementary information is available on the Nature Immunology website. AUTHORS CONTRIBUTIONS T.K.M., Z.G.R., and W.F.P. III planned the research, analyzed and interpreted data and wrote the manuscript. Z.G.R. performed most of the experiments. C.J.B helped with mouse breeding and genotyping. W.F.P. III, A.P., and T.I. performed and analyzed ELISAs, PCR, and mouse pathology. N.H. and A.D.L. analyzed and interpreted data. T.K.M., J.E.K., and M.H.B. contributed to the generation of SCARF1-deficient mice. All authors participated in editing the manuscript into its final form. COMPETING FINANCIAL INTERESTSThe authors declare no competing financial interests. HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript both professional scavengers (macrophages, DCs) and non-professional phagocytes (fibroblasts, endothelial, and epithelial cells). In vivo, phagocytes are responsible for the rapid removal of dying cells before necrosis, a post-apoptotic stage accompanied by loss of membrane integrity and leakage of noxious intracellular molecules into the surrounding tissues 4,5 . Phagocyte engulfment of apoptotic cells occurs via an immunologically silent process by activating immunosuppressive pathways and the production of anti-inflammatory cytokines to prevent an immune response against self-antigens 6 . Consequently, defects in recognition and/or engulfment of apoptotic cells can lead to chronic inflammatory diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis, glomerulonephritis and at...

Phagocytic defenses are critical for effective host defenses against the opportunistic fungal pathogen Aspergillus fumigatus. Previous studies found that following challenge with A. fumigatus, Toll-like receptor 9 (TLR9) knockout mice survived longer than wild-type mice. However, the mechanism responsible was not defined. Here we demonstrate that A. fumigatus contains unmethylated CpG sequences, the natural ligands for TLR9. A. fumigatus DNA and synthetic CpG-rich oligodeoxynucleotides (ODNs) containing sequences found in the A. fumigatus genome potently stimulated the production of proinflammatory cytokines in mouse bone marrow-derived dendritic cells (BMDCs) and human plasmacytoid dendritic cells. The response was decreased when the fungal DNA was treated with a CpG methylase or with CpG-specific endonucleases. A role for TLR9 was demonstrated as cytokine production was abolished in BMDCs from TLR9-deficient mice. Moreover, transfection of HEK293 cells with human TLR9 conferred responsiveness to synthetic CpG-rich ODNs containing sequences found in A. fumigatus DNA. Taken together, these data demonstrate that TLR9 detects A. fumigatus DNA, resulting in the secretion of proinflammatory cytokines, which may contribute to the immune response to the pathogen.

Summary CARD9 is a central component of anti-fungal innate immune signaling via C-type lectin receptors, and several immune-related disorders are associated with CARD9 mutations. Here we used a rare CARD9 variant that confers protection against inflammatory bowel disease as an entry point to investigate CARD9 regulation. We showed that the C-terminal truncated CARD9 protective variant acted in a dominant negative manner for CARD9-mediated cytokine production, indicating an important role for the C terminus in CARD9 signaling. We identified TRIM62 as a CARD9 binding partner and showed that TRIM62 facilitated K27-linked poly-ubiquitination of CARD9. We identified K125 as the ubiquitinated residue on CARD9 and demonstrated that this ubiquitination was essential for CARD9 activity. Furthermore, we showed that Trim62-deficient mice have increased susceptibility to fungal infection, similar to Card9-deficient mice. This study utilizes a rare protective allele to uncover a TRIM62-mediated mechanism for regulation of CARD9 activation.