title: Cholera toxin impairs the differentiation of monocytes into dendritic cells, inducing professional antigen-presenting myeloid cells.
abstract: Cholera toxin (CT) is a potent adjuvant for mucosal vaccination; however, its mechanism of action has not been clarified completely. It is well established that peripheral monocytes differentiate into dendritic cells (DCs) both in vitro and in vivo and that monocytes are the in vivo precursors of mucosal CD103(-) proinflammatory DCs. In this study, we asked whether CT had any effects on the differentiation of monocytes into DCs. We found that CT-treated monocytes, in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 4 (IL-4), failed to differentiate into classical DCs (CD14(low) CD1a(high)) and acquired a macrophage-like phenotype (CD14(high) CD1a(low)). Cells differentiated in the presence of CT expressed high levels of major histocompatibility complex class I (MHC-I) and MHC-II and CD80 and CD86 costimulatory molecules and produced larger amounts of IL-1β, IL-6, and IL-10 but smaller amounts of tumor necrosis factor alpha (TNF-α) and IL-12 than did monocytes differentiated into DCs in the absence of CT. The enzymatic activity of CT was found to be important for the skewing of monocytes toward a macrophage-like phenotype (Ma-DCs) with enhanced antigen-presenting functions. Indeed, treatment of monocytes with scalar doses of forskolin (FSK), an activator of adenylate cyclase, induced them to differentiate in a dose-dependent manner into a population with phenotype and functions similar to those found after CT treatment. Monocytes differentiated in the presence of CT induced the differentiation of naïve T lymphocytes toward a Th2 phenotype. Interestingly, we found that CT interferes with the differentiation of monocytes into DCs in vivo and promotes the induction of activated antigen-presenting cells (APCs) following systemic immunization.
authors.affiliation: Department of Infectious, Parasitic, and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena, 00161 Rome, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Veglia
authors.forename: Ester
authors.initials: E
authors.lastname: Sciaraffia
authors.forename: Antonella
authors.initials: A
authors.lastname: Riccomi
authors.forename: Dora
authors.initials: D
authors.lastname: Pinto
authors.forename: Donatella R M
authors.initials: DR
authors.lastname: Negri
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: De Magistris
authors.forename: Silvia
authors.initials: S
authors.lastname: Vendetti
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D000938:Antigen-Presenting Cells / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D002454:Cell Differentiation / Q000187:drug effects* / Q000276:immunology; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology*; D003713:Dendritic Cells / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D005260:Female; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic; D009000:Monocytes / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D022423:Myeloid Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D010641:Phenotype
chemical_list: D000276:Adjuvants, Immunologic; D002772:Cholera Toxin