title: Lipoteichoic acid preparations of gram-positive bacteria induce interleukin-12 through a CD14-dependent pathway.
abstract: Interleukin 12 (IL-12) strongly augments gamma interferon production by natural killer (NK) and T cells. IL-12 also promotes effective cell-mediated immune responses, which are particularly important against intracellular bacteria such as Listeria monocytogenes. While the lipopolysaccharide (LPS) of gram-negative bacteria induces monocyte production of IL-12, the relevant gram-positive components which induce IL-12 production are uncharacterized. We used the human monocytic cell line THP-1 to study IL-12 induction by gram-positive bacteria. Muramyl dipeptides as well as the major muramyl tetrapeptide component of Streptococcus pneumoniae were inactive for inducing IL-12. In contrast, lipoteichoic acid (LTA), a predominant surface glycolipid of gram-positive bacteria, potently induced IL-12 p40 gene expression. A competitive LPS antagonist, Rhodobacter sphaeroides LPS, inhibited LTA-induced IL-12 production, suggesting a common pathway for LPS and LTA in IL-12 activation. Pretreatment of cells with anti-CD14 monoclonal antibody blocked both LPS and LTA induction of IL-12 p40 expression. LTA also induced Thl development in naive CD4 T cells by an IL-12-dependent mechanism, indicating direct induction of physiologic levels of IL-12. Together, these results show that LTA is a potent surface structure of gram-positive bacteria which induces IL-12 in monocytes through a CD14-mediated pathway.
authors.affiliation: Division of Dermatology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Cleveland
authors.forename: J D
authors.initials: JD
authors.lastname: Gorham
authors.forename: T L
authors.initials: TL
authors.lastname: Murphy
authors.forename: E
authors.initials: E
authors.lastname: Tuomanen
authors.forename: K M
authors.initials: KM
authors.lastname: Murphy
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D001483:Base Sequence; D006801:Humans; D018664:Interleukin-12 / Q000096:biosynthesis*; D018950:Lipopolysaccharide Receptors / Q000502:physiology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008969:Molecular Sequence Data; D013682:Teichoic Acids / Q000494:pharmacology*; D018417:Th1 Cells / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D013682:Teichoic Acids; D018664:Interleukin-12; C009900:lipoteichoic acid