DC-LAMP Dendritic Cells Are Recruited to Gastric Lymphoid Follicles in Helicobacter pylori-Infected Individuals

Infection withHelicobacter pylori is associated with development of ulcer disease and gastrointestinal adenocarcinoma. The infection leads to a large infiltration of immune cells and the formation of organized lymphoid follicles in the human gastric mu-cosa. Still, the immune system fails to eradicate the bacteria, and the substantial regulatory T cell (Treg) response elicited is probably a major factor permitting bacterial persistence. Dendritic cells (DCs) are professional antigen-presenting cells that can activate naive T cells, andmaturation of DCs is crucial for the initiation of primary immune responses. The aim of this study was to investigate the presence and localization of mature human DCs inH. pylori-infected gastric mucosa. Gastric antral biopsy specimens were collected from patients withH. pylori-associated gastritis and healthy volunteers, and antrum tissue was col-lected from patients undergoing gastric resection. Immunohistochemistry and flow cytometry showed that DCs expressing the maturation marker dendritic cell lysosome-associatedmembrane glycoprotein (DC-LAMP; CD208) are enriched in theH. pylori-infected gastric mucosa and that these DCs are specifically localized within or close to lymphoid follicles. Gastric DC-LAMP-positive (DC-LAMP) DCs express CD11c and high levels of HLA-DR but little CD80, CD83, and CD86. Furthermore, immuno-fluorescence analyses demonstrated that DC-LAMPDCs are in the same location as FoxP3-positive putative Tregs in the folli-cles. In conclusion, we show that DC-LAMPDCs with low costimulatory capacity accumulate in the lymphoid follicles in humanH. pylori-infected gastric tissue, and our results suggest that Treg-DC interactions may promote chronic infection by rendering gastric DCs tolerogenic