Functions of dendritic-cell-bound IgE in allergy

Immunoglobulin E (IgE) functions as an Fc-receptor-bound antigen sensor for mast cells and basophils, the classical effector cells of allergy. A cell-bound IgE pool is formed when monomeric IgE binds to Fc epsilon RI, the high affinity IgE Pc receptor on these cells, and minor amounts of antigen are sufficient to trigger the pro-allergic innate IgE effector axis. Additionally, Fc epsilon RI is constitutively expressed on human dendritic cells (DCs), and thus the latter cell type also receives signals via cell-bound IgE. Notably, steady-state expression of Fc epsilon RI on DCs is absent in SPF-housed mice. How DCs integrate IgE/Fc epsilon Rl-derived signals into their sentinel functions as gatekeepers of immunity was therefore only recently studied with transgenic mice that phenocopy human Fc epsilon RI expression. In this review, we summarize advances in our understanding of the functions of DC-bound IgE which demonstrate that IgE-mediated activation of DCs in allergic Th2-type inflammation appears to be immune regulatory rather than pro-inflammatory. (C) 2015 Elsevier Ltd. All rights reserved.