title: Characterization of Siglec-H as a novel endocytic receptor expressed on murine plasmacytoid dendritic cell precursors.
abstract: We describe the cloning and characterization of Siglec-H, a novel murine CD33-related siglec-like molecule with 2 immunoglobulin domains. Unlike other CD33-related siglecs, Siglec-H lacks tyrosine-based signaling motifs in its cytoplasmic tail. Although Siglec-H has the typical structural features required for sialic acid binding, no evidence for carbohydrate recognition was obtained. Specific monoclonal and polyclonal antibodies (Abs) were raised to Siglec-H and used to define its cellular expression pattern and functional properties. By flow cytometry, Siglec-H was expressed specifically on plasmacytoid dendritic cell (pDC) precursors in bone marrow, spleen, blood, and lymph nodes. Staining of tissue sections showed that Siglec-H was also expressed in a subset of marginal zone macrophages in the spleen and in medullary macrophages in lymph nodes. Using bone marrow-derived pDC precursors that express Siglec-H, addition of Abs did not influence cytokine production, either in the presence or absence of synthetic oligodeoxynucleotides containing unmethylated cytosine-guanine motifs (CpG). In comparison, Siglec-H functioned as an endocytic receptor and mediated efficient internalization of anti-Siglec-H Abs. By immunizing mice with ovalbumin-conjugated anti-Siglec-H Ab in the presence of CpG, we demonstrate generation of antigen-specific CD8 T cells in vivo. Targeting Siglec-H may therefore be a useful way of delivering antigens to pDC precursors for cross-presentation.
authors.affiliation: Division of Cell Biology and Immunology, School of Life Sciences, Wellcome Trust Biocentre at Dundee, University of Dundee, Dundee DD1 5EH, United Kingdom.
authors.forename: Jiquan
authors.initials: J
authors.lastname: Zhang
authors.forename: Anna
authors.initials: A
authors.lastname: Raper
authors.forename: Noriko
authors.initials: N
authors.lastname: Sugita
authors.forename: Ravi
authors.initials: R
authors.lastname: Hingorani
authors.forename: Mariolina
authors.initials: M
authors.lastname: Salio
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Palmowski
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Cerundolo
authors.forename: Paul R
authors.initials: PR
authors.lastname: Crocker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D001483:Base Sequence; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D004705:Endocytosis / Q000276:immunology*; D015870:Gene Expression; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D010950:Plasma Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000235:genetics* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D063268:Sialic Acid Binding Ig-like Lectin 3
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; C571165:Cd33 protein, mouse; D018076:DNA, Complementary; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins; D063268:Sialic Acid Binding Ig-like Lectin 3; D019158:N-Acetylneuraminic Acid