title: Effect of sialic acid loss on dendritic cell maturation.
abstract: Sialic acids are key structural determinants and contribute to the functionality of a number of immune cell receptors. Previously, we demonstrated that differentiation of human dendritic cells (DCs) is accompanied by an increased expression of sialylated cell surface structures, putatively through the activity of the ST3Gal.I and ST6Gal.I sialyltransferases. Furthermore, DC endocytosis was reduced upon removal of the cell surface sialic acid residues by neuraminidase. In the present work, we evaluate the contribution of the sialic acid modifications in DC maturation. We demonstrate that neuraminidase-treated human DCs have increased expression of major histocompatibility complex (MHC) and costimulatory molecules, increased gene expression of specific cytokines and induce a higher proliferative response of T lymphocytes. Together, the data suggest that clearance of cell surface sialic acids contributes to the development of a T helper type 1 proinflammatory response. This postulate is supported by mouse models, where elevated MHC class II and increased maturation of specific DC subsets were observed in DCs harvested from ST3Gal.I(-/-) and ST6Gal.I(-/-) mice. Moreover, important qualitative differences, particularly in the extent of reduced endocytosis and in the peripheral distribution of DC subsets, existed between the ST3Gal.I(-/-) and ST6Gal.I(-/-) strains. Together, the data strongly suggest not only a role of cell surface sialic acid modifications in maturation and functionality of DCs, but also that the sialic acid linkages created by different sialyltransferases are functionally distinct. Consequently, with particular relevance to DC-based therapies, cell surface sialylation, mediated by individual sialyltransferases, can influence the immunogenicity of DCs upon antigen loading.
authors.affiliation: Departamento de Imunologia FCM-UNL, Campo Mártires da Pátria 130, Lisboa, Portugal.
authors.forename: Hélio J
authors.initials: HJ
authors.lastname: Crespo
authors.forename: M Guadalupe
authors.initials: MG
authors.lastname: Cabral
authors.forename: Alexandra V
authors.initials: AV
authors.lastname: Teixeira
authors.forename: Joseph T Y
authors.initials: JT
authors.lastname: Lau
authors.forename: Hélder
authors.initials: H
authors.lastname: Trindade
authors.forename: Paula A
authors.initials: PA
authors.lastname: Videira
mesh_terms: D000818:Animals; D018122:B7-1 Antigen / Q000187:drug effects / Q000276:immunology; D051940:B7-2 Antigen / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000187:drug effects / Q000276:immunology; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology*; D004705:Endocytosis / Q000276:immunology; D006649:Histocompatibility Antigens / Q000187:drug effects / Q000276:immunology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009439:Neuraminidase / Q000494:pharmacology; D012794:Sialic Acids / Q000276:immunology*; D012799:Sialyltransferases / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase
chemical_list: D018122:B7-1 Antigen; D051940:B7-2 Antigen; D016207:Cytokines; D006649:Histocompatibility Antigens; D012794:Sialic Acids; D012799:Sialyltransferases; D009439:Neuraminidase; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase