Relationship between Helicobacter pylori Infection and Plasmacytoid and Myeloid Dendritic Cells in Peripheral Blood and Gastric Mucosa of Children

PURPOSE: To investigate the frequency and activation status of peripheral plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) as well as gastric mucosa DC subset distribution in Helicobacter pylori- (H. pylori-) infected and noninfected children. MATERIALS AND METHODS: Thirty-six children were studied; twenty-one had H. pylori. The frequencies of circulating pDCs (lineage(−)HLA-DR(+)CD123(+)) and mDCs (lineage(−)HLA-DR(+)CD11c(+)) and their activation status (CD83, CD86, and HLA-DR expression) were assessed by flow cytometry. Additionally, the densities of CD11c(+), CD123(+), CD83(+), CD86(+), and LAMP3(+) cells in the gastric mucosa were determined by immunohistochemistry. RESULTS: The frequency of circulating CD83(+) mDCs was higher in H. pylori-infected children than in the noninfected controls. The pDCs demonstrated upregulated HLA-DR surface expression, but no change in CD86 expression. Additionally, the densities of gastric lamina propria CD11c(+) cells and epithelial pDCs were increased. There was a significant association between frequency of circulating CD83(+) mDCs and gastric lamina propria mDC infiltration. CONCLUSION: This study shows that although H. pylori-infected children had an increased population of mature mDCs bearing CD83 in the peripheral blood, they lack mature CD83(+) mDCs in the gastric mucosa, which may promote tolerance to local antigens rather than immunity. In addition, this may reduce excessive inflammatory activity as reported for children compared to adults.