title: Streptococcus pyogenes activates human plasmacytoid and myeloid dendritic cells.
abstract: Human peripheral blood contains two major dendritic cell (DC) populations, namely CD11c(-)CD123+ plasmacytoid DCs (PDCs) and CD11c+CD123(-) myeloid DCs (MDCs). Although the activation of these DC types by various TLR ligands has been relatively well-characterized, less is known about the ability of whole live bacteria to induce PDC and MDC activation. In the present report, we have compared the activation of human PDCs and MDCs in response to major human bacterial pathogen Streptococcus pyogenes (group A streptococci) and influenza A virus. S. pyogenes stimulation resulted in the maturation of both DC types, as evidenced by enhanced expression of costimulatory molecules and production of proinflammatory cytokines and chemokines. Furthermore, S. pyogenes-stimulated PDCs and MDCs activated naïve CD4+ T cells and enhanced their Th1 cytokine production. Influenza A virus infection induced rapid PDC activation, whereas MDCs were extremely sensitive to influenza A virus-induced cell death. The most significant differences between DC types were seen in the production of IL-10 and IL-12, which were only produced by S. pyogenes-stimulated MDCs. Although S. pyogenes was able to induce PDC activation, only influenza A virus infection resulted in detectable IFN-alpha production. Our results show that depending on the infecting microbe, the functions of PDCs and MDCs may be partially overlapping, suggesting a considerable flexibility of the human DC system.
authors.affiliation: Department of Viral Diseases and Immunology, National Public Health Institute, Mannerheimintie 166, FI-00300 Helsinki, Finland. ville.veckman@ktl.fi
authors.forename: Ville
authors.initials: V
authors.lastname: Veckman
authors.forename: Ilkka
authors.initials: I
authors.lastname: Julkunen
mesh_terms: D000328:Adult; D015703:Antigens, CD / Q000032:analysis; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D002454:Cell Differentiation; D018925:Chemokines / Q000096:biosynthesis / Q000378:metabolism; D016207:Cytokines / Q000096:biosynthesis / Q000378:metabolism; D003713:Dendritic Cells / Q000145:classification / Q000276:immunology*; D006681:HLA-D Antigens / Q000096:biosynthesis; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology; D022423:Myeloid Cells / Q000276:immunology; D013297:Streptococcus pyogenes / Q000276:immunology*; D018417:Th1 Cells / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D018925:Chemokines; D016207:Cytokines; D006681:HLA-D Antigens