The high-affinity Fc receptor molecules for IgE (FcεRI) are mainly expressed in mast cells and basophils, leading to hypersensitivity reactions. Previous studies have shown that human dendritic cells (DCs) in the peripheral blood express FcεRI on their surface, yet the specific role of FcεRI has not been clarified. We obtained immature monocyte-derived DCs (iDCs) from human peripheral blood and confirmed the expression of FcεRI. To reveal the function of FcεRI on iDCs, we specifically crosslinked FcεRI, and showed the production of interleukin (IL)-6 and tumor necrosis factor alpha (TNFα). We then co-cultured FcεRI-stimulated DCs with human leukocyte antigen - antigen D related (HLA-DR) non-shared allogeneic CD4+ naïve T cells, and showed that they led to the differentiation of naïve T cells toward the T helper 1 subset. This differentiation was inhibited by anti-IL-12 antibodies, and FcεRI-stimulated DCs enhanced the production of IL-12 upon antigen presentation. This should be a novel evidence of a negative feedback loop of allergic IgE responses via FcεRI on DCs.
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