title: Simultaneous blocking of human Toll-like receptors 2 and 4 suppresses myeloid dendritic cell activation induced by Mycobacterium bovis bacillus Calmette-Guérin peptidoglycan.
abstract: The Mycobacterium bovis bacillus Calmette-Guérin (BCG) cell wall skeleton (CWS) consists of mycolic acids, arabinogalactan, and peptidoglycan (PGN) and activates Toll-like receptor 2 (TLR2) and TLR4. Here we investigated the ability of the essential portion of highly purified BCG CWS to support the TLR agonist function by using the following criteria: myeloid dendritic cell (DC) maturation, i.e., tumor necrosis factor alpha (TNF-alpha) production and CD83/CD86 up-regulation. The purified PGN region was sufficient to activate TLR2 and TLR4 in mouse DCs and macrophages; in TLR2 and TLR4 double-knockout cells the BCG PGN-mediated TNF-alpha production ability was completely impaired. Likewise, stimulation with BCG CWS of HEK293 cells expressing either human TLR2 or TLR4, MD-2, and CD14 resulted in NF-kappa B activation as determined by a reporter assay. Notably, specific blockers of extracellular human TLR2 (an original cocktail of monoclonal antibodies TLR2.45 and TH2.1) and TLR4 (E5531) inhibited BCG CWS-mediated NF-kappa B activation by 80%. Using this human TLR blocking system, we tested whether human myeloid DC maturation was TLR2 and TLR4 dependent. BCG PGN-mediated DC maturation was blocked by 70% by suppression of both TLR2 and TLR4 and by 30 to 40% by suppression of either of these TLRs. Similar but less profound suppression of BCG CWS-mediated DC maturation was observed. Hence, the presence of BCG PGN is a minimal requirement for activation of both TLR2 and TLR4 in human DCs, unlike the presence of PGNs of gram-positive bacteria, which activate only TLR2. Unexpectedly, however, BCG PGN, unlike BCG CWS, barely activated NF-kappa B in HEK293 cells coexpressing TLR2 plus TLR1, TLR2 plus TLR4, TLR2 plus TLR6, or TLR2 plus TLR10, suggesting that PGN receptors other than TLR2 and TLR4 present on human DCs but not on HEK293 cells are involved in TLR signaling for DC activation.
authors.affiliation: Department of Immunology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Higashinari-ku, Osaka 537-8511, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Uehori
authors.forename: Misako
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Shoutaro
authors.initials: S
authors.lastname: Tsuji
authors.forename: Takashi
authors.initials: T
authors.lastname: Akazawa
authors.forename: Osamu
authors.initials: O
authors.lastname: Takeuchi
authors.forename: Shizuo
authors.initials: S
authors.lastname: Akira
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kawata
authors.forename: Ichiro
authors.initials: I
authors.lastname: Azuma
authors.forename: Kumao
authors.initials: K
authors.lastname: Toyoshima
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Seya
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002473:Cell Wall / Q000737:chemistry / Q000276:immunology; D003713:Dendritic Cells / Q000166:cytology / Q000187:drug effects* / Q000276:immunology*; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009163:Mycobacterium bovis / Q000737:chemistry / Q000276:immunology*; D010457:Peptidoglycan / Q000378:metabolism / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000378:metabolism; D051194:Toll-Like Receptor 1; D051201:Toll-Like Receptor 10; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
chemical_list: D000911:Antibodies, Monoclonal; D008562:Membrane Glycoproteins; D010457:Peptidoglycan; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051194:Toll-Like Receptor 1; D051201:Toll-Like Receptor 10; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors