Pathogenic bacteria and dead cells are internalized by a unique subset of Peyer's patch dendritic cells that express lysozyme.
OBJECTIVE
Lysozyme has an important role in preventing bacterial infection. In the gastrointestinal tract, lysozyme is thought to be mainly expressed by Paneth cells of the crypt epithelium. We investigated its expression in the Peyer's patch, a major intestinal site of antigen sampling and pathogen entry.


METHODS
We performed immunostaining on normal and Salmonella Typhimurium-infected intestinal samples and analyzed them by confocal microscopy and flow cytometry.


RESULTS
In Peyer's patch of mouse, rat, and human, lysozyme was strongly expressed in the germinal center of follicles by tingible body macrophages and in the subepithelial dome by a subset of myeloid dendritic cells (DC). Among DC subsets from mouse Peyer's patches, these lysozyme-expressing DC displayed the highest surface expression of class II major histocompatibility complex and costimulatory molecules; they were the most efficient at capturing microspheres in vitro. Moreover, they were the main DC subset involved in bacterial pathogen uptake and in dead cell clearance, including M cells.


CONCLUSIONS
The subepithelial dome of Peyer's patches contains a unique population of intestinal DC that secretes high levels of lysozyme and internalizes bacteria and dead cells.
Aix Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy, Marseille, France.
Hugues
H
Lelouard
Sandrine
S
Henri
Béatrice
B
De Bovis
Bénédicte
B
Mugnier
Alexandre
A
Chollat-Namy
Bernard
B
Malissen
Stéphane
S
Méresse
Jean-Pierre
JP
Gorvel
D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D039481:CD11b Antigen / Q000378:metabolism; D039521:CD11c Antigen / Q000378:metabolism; D000073883:CX3C Chemokine Receptor 1; D003713:Dendritic Cells / Q000201:enzymology / Q000276:immunology / Q000382:microbiology; D004751:Enteritis / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008264:Macrophages / Q000201:enzymology / Q000276:immunology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D009113:Muramidase / Q000378:metabolism*; D022423:Myeloid Cells / Q000201:enzymology / Q000276:immunology / Q000382:microbiology; D010581:Peyer's Patches / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D051381:Rats; D019707:Receptors, Chemokine / Q000378:metabolism; D012480:Salmonella Infections / Q000276:immunology* / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000472:pathogenicity
D000943:Antigens, Differentiation; D039481:CD11b Antigen; D039521:CD11c Antigen; D000073883:CX3C Chemokine Receptor 1; C095235:CX3CR1 protein, human; C516305:CX3CR1 protein, rat; C471885:Cx3cr1 protein, mouse; C509295:ITGAM protein, human; D019707:Receptors, Chemokine; C036763:monocyte-macrophage differentiation antigen; D009113:Muramidase