title: The omentum is a site of protective IgM production during intracellular bacterial infection.
abstract: Infection of mice with the bacterium Ehrlichia muris elicits a protective T cell-independent (TI) IgM response mediated primarily by a population of CD11c-expressing plasmablasts in the spleen. Although splenic marginal zone (MZ) B cells are considered to be important for TI responses to blood-borne pathogens, MZ B cells were not responsible for generating plasmablasts in response to Ehrlichia muris. Moreover, antigen-specific serum IgM was decreased only modestly in splenectomized mice and in mice that lacked spleen, lymph nodes, and Peyer's patches (SLP mice). Both splenectomized and SLP mice were protected against lethal ehrlichial challenge infection. Moreover, we found a high frequency of Ehrlichia-specific plasmablasts in the omentum of both conventional and SLP mice. Omental plasmablasts elicited during Ehrlichia infection lacked expression of CD138 but expressed CD11c in a manner similar to that of their splenic counterparts. Selective ablation of CD11c-expressing B cells nearly eliminated the omental Ehrlichia-specific plasmablasts and reduced antigen-specific serum IgM, identifying the omental B cells as a source of IgM production in the SLP mice. Generation of the omental plasmablasts was route dependent, as they were detected following peritoneal infection but not following intravenous infection. Our data identify the omentum as an important auxiliary site of IgM production during intracellular bacterial infection.
authors.affiliation: Department of Biomedical Sciences, University at Albany, Albany, New York, USA.
authors.forename: Derek D
authors.initials: DD
authors.lastname: Jones
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York, USA.
authors.forename: Rachael
authors.initials: R
authors.lastname: Racine
authors.affiliation: Trudeau Institute, Saranac Lake, New York, USA.
authors.forename: Susan T
authors.initials: ST
authors.lastname: Wittmer
authors.affiliation: Trudeau Institute, Saranac Lake, New York, USA.
authors.forename: Louise
authors.initials: L
authors.lastname: Harston
authors.affiliation: Upstate Medical University, Syracuse, New York, USA.
authors.forename: Amber M
authors.initials: AM
authors.lastname: Papillion
authors.affiliation: Upstate Medical University, Syracuse, New York, USA.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Dishaw
authors.affiliation: Trudeau Institute, Saranac Lake, New York, USA.
authors.forename: Troy D
authors.initials: TD
authors.lastname: Randall
authors.affiliation: Trudeau Institute, Saranac Lake, New York, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Woodland
authors.affiliation: Department of Biomedical Sciences, University at Albany, Albany, New York, USA Trudeau Institute, Saranac Lake, New York, USA Wadsworth Center, New York State Department of Health, Albany, New York, USA winslowg@upstate.edu.
authors.forename: Gary M
authors.initials: GM
authors.lastname: Winslow
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000378:metabolism*; D039521:CD11c Antigen / Q000032:analysis; D004536:Ehrlichia / Q000276:immunology; D016873:Ehrlichiosis / Q000276:immunology*; D005260:Female; D007075:Immunoglobulin M / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009852:Omentum / Q000276:immunology* / Q000473:pathology; D010950:Plasma Cells / Q000276:immunology*; D053668:Syndecan-1 / Q000032:analysis
chemical_list: D000907:Antibodies, Bacterial; D039521:CD11c Antigen; D007075:Immunoglobulin M; C508242:Sdc1 protein, mouse; D053668:Syndecan-1