title: Salmonella inhibits monocyte differentiation into CD11c hi MHC-II hi cells in a MyD88-dependent fashion.
abstract: Monocytes and DCs originate from a shared precursor in the bone marrow, and steady-state DCs in lymphoid organs develop directly from the precursor rather than via a monocyte intermediate. However, monocytes can differentiate into DCs in tissues such as the lung and gut mucosa and into macrophages in most tissues. As Ly6C hi monocytes accumulate in lymphoid organs during oral Salmonella infection, we investigated their ability to develop into potential DCs, identified as CD11c hi MHC-II hi cells, in infected hosts. Ly6C hi monocytes, isolated from the blood of Salmonella-infected mice, developed into CD11c hi MHC-II hi cells after culture with GM-CSF or Flt3L. In contrast, the same monocytes cultured in the presence of GM-CSF and heat-killed Salmonella did not differentiate into CD11c hi MHC-II hi cells. The bacteria-induced differentiation block was dependent on TLRs, as monocytes from MyD88-/- mice converted into CD11c hi MHC-II hi cells even in the presence of bacteria. We hypothesized that Salmonella-activated wild-type monocytes secreted mediators that inhibited differentiation of MyD88-/--derived monocytes. However, IL-6, IL-10, TNF-alpha, or IL-12p70 did not account for the inhibition. Finally, monocyte-derived CD11c hi MHC-II hi cells pulsed with OVA peptide or protein did not induce proliferation of antigen-specific CD4+ T cells but rather, suppressed the ability of DCs to activate CD4+ T cells. Overall, the data show that Ly6C hi monocytes from Salmonella-infected mice develop into CD11c hi MHC-II hi cells with poor antigen-presentation capacity when cultured ex vivo, and that monocyte exposure to Salmonella inhibits their differentiation into CD11c hi MHC-II hi cells in a MyD88-dependent fashion.
authors.affiliation: Department of Microbiology and Immunology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Rydström
authors.forename: Mary Jo
authors.initials: MJ
authors.lastname: Wick
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology; D039521:CD11c Antigen / Q000096:biosynthesis / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology*; D002469:Cell Separation; D016207:Cytokines / Q000096:biosynthesis; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis / Q000276:immunology*; D007959:Lymphocyte Culture Test, Mixed; D051379:Mice; D009000:Monocytes / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000096:biosynthesis / Q000276:immunology; D012475:Salmonella / Q000276:immunology; D012480:Salmonella Infections / Q000276:immunology*
chemical_list: D039521:CD11c Antigen; D016207:Cytokines; D000949:Histocompatibility Antigens Class II; D053594:Myeloid Differentiation Factor 88