Serum IgE clearance is facilitated by human FcεRI internalization
Alexandra M. Greer, … , Jean-Pierre Kinet, Jeoung-Sook Shin
Alexandra M. Greer, … , Jean-Pierre Kinet, Jeoung-Sook Shin
Published February 24, 2014
Citation Information: J Clin Invest. 2014;124(3):1187-1198. https://doi.org/10.1172/JCI68964.
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Research Article Immunology

Serum IgE clearance is facilitated by human FcεRI internalization

Abstract

The high-affinity IgE receptor FcεRI is constitutively expressed in mast cells and basophils and is required for transmitting stimulatory signals upon engagement of IgE-bound allergens. FcεRI is also constitutively expressed in dendritic cells (DCs) and monocytes in humans; however, the specific functions of the FcεRI expressed by these cells are not completely understood. Here, we found that FcεRI expressed by human blood DC antigen 1–positive (BDCA1+) DCs and monocytes, but not basophils, traffics to endolysosomal compartments under steady-state conditions. Furthermore, IgE bound to FcεRI on BDCA1+ DCs was rapidly endocytosed, transported to the lysosomes, and degraded in vitro. IgE injected into mice expressing human FcεRIα (FCER1A-Tg mice) was endocytosed by conventional DCs and monocytes, and endocytosis was associated with rapid clearance of circulating IgE from these mice. Importantly, this rapid IgE clearance was dependent on monocytes or DCs but not basophils. These findings strongly suggest that constitutive internalization of human FcεRI by DCs and monocytes distinctively contributes to serum IgE clearance.

Authors

Alexandra M. Greer, Nan Wu, Amy L. Putnam, Prescott G. Woodruff, Paul Wolters, Jean-Pierre Kinet, Jeoung-Sook Shin

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Figure 3

IgE bound to FcεRI on DCs is efficiently internalized.

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IgE bound to FcεRI on DCs is efficiently internalized. (A) Intracellular...
(A) Intracellular IgE in basophils and DCs. The basophil image is representative of 83 recorded images from 7 unique and representative donors, and the DC image is representative of 121 recorded images from 9 unique and representative donors. Original magnification, ×60 and scale bars are 2.5 μm. (B) Intracellular IgE was quantified by flow cytometry. Isolated basophils and DCs were washed with acid (see Methods for detail) or PBS. Data are mean ± SEM for 8 representative donors. (C) Entry of hIgE-A647 into basophils and DCs of one representative donor. hIgE-A647 (0.5 μg/ml) was added to PBMCs. At each indicated time point, cells were treated with acid or PBS before permeabilization and analysis by flow cytometry. (D) IgE entry to basophils and DCs is IgE receptor mediated. PBMCs were incubated for 4 hours with hIgE-A647 (0.5 μg/ml) alone (left), with excess unlabeled IgE (middle), or IgG (40 μg/ml) (right). Cells incubated with hIgE-A647 alone were washed with acid or unwashed. Cells incubated together with excess IgE or IgG were all washed with acid. Then, the A647 MFI of acid-washed cells was divided by that of unwashed cells to comparatively determine intracellular IgE content. Data are mean ± SEM for 4 representative donors.