Expression of High-Affinity IgE Receptor on Human Peripheral Blood Dendritic Cells in Children

BACKGROUND: In a mouse model of viral induced atopic disease, expression of FcεRI on dendritic cells is critical. While adult human conventional (cDC) and plasmacytoid (pDC) dendritic cells have been shown to express FcεRI, it is not known if this receptor is expressed in childhood and how its expression is governed by IgE. METHODS: Following informed consent of subjects (n = 27, aged 12-188 months), peripheral blood was stained for surface expression of CD19, ILT7, CD1c, IgE, FcεRI and analyzed by flow cytometry (cDC: CD19(-) ILT7(-) CD1c(+); pDC: CD19(-) ILT7(+) CD1c(-)). Total and specific serum IgE levels to food and inhalant allergens were determined by ImmunoCAP, and the relationship between FcεRI expression on dendritic cells and sensitization, free IgE, cell bound IgE, and age was determined. RESULTS: Independent of sensitization status, FcεRI expression was noted on cDC and pDC as early as 12 months of age. Serum IgE level correlated with expression of FcεRI on cDC, but not pDC. Based on the concentration of IgE, a complex relationship was found between surface bound IgE and expression of FcεRI on cDC. pDC exhibited a linear relationship of FcεRI expression and bound IgE that was consistent through all IgE concentrations. CONCLUSIONS: In children, FcεRI expression on cDC and pDC is modulated differently by serum and cell bound IgE. IgE governance of FcεRI expression on cDC depends upon a complex relationship. Further studies are needed to determine the functional roles of FcεRI on cDC and pDC

Comparison of Sensitized and Non-Sensitized Children for Dendritic Cell Expression of IgE and FcεRI.

†<p>: Mann-Whitney test.</p><p>IQR: interquartile range, cDC: conventional dendritic cells, pDC: plasmacytoid dendritic cells.</p

Sensitization status regression models with significant Pearson correlations.

<p>Ln indicates the natural log transformation.</p

Subject Characteristics.

<p>*Atopy history: defined as self reported or MD diagnosed allergic rhinitis/hayfever/environmental allergies, asthma/wheeze, atopic dermatitis, food allergy. Family history of atopy was based on self-reporting only.</p>†<p>Sensitized: defined as any elevated food or inhalant serum specific IgE.</p>§<p>Only 4 of these subjects had a clinical history suggestive of an allergy for the foods to which they had IgE against.</p

Correlation of cDC expression of FcεRI with IgE.

<p>Expression of FcεRI and IgE on the surface of cDC was determined by flow cytometry. (A) Data are presented as fold MFI FcεRI versus fold MFI IgE expression, with non-sensitized subjects (n = 15) in red circles and sensitized subjects (n = 12) in black x's. Note the difference in the slope of the fitted lines (non-sensitized subjects in red dotted line; sensitized subjects in black solid line) above and below a fold MFI IgE of 12, suggesting that there is differential regulation of FcεRI on cDC around this level of cell bound IgE. For all subjects the data was fit with the following cubic equation (blue line): Ln(cDC FcεRI) = 2.26+0.72*ln(cDC IgE)-0.43*ln(cDC IgE)²+0.082*ln(cDC IgE)³); r = 0.86; p = 0.045. For equations based on sensitization status, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032556#pone-0032556-t003" target="_blank">Table 3</a>. (B) Expression of cell bound IgE on cDC compared with serum (free) IgE levels. Data are presented as in (A) with fold MFI IgE expression versus serum IgE (kU/L). Note that a cell bound IgE fold MFI of 12 correlates with a serum IgE of around 38 (based on statistical fitting of the curve, this value could range between 34 and 42 kU/L).</p

Expression of FcεRI on pDC does not correlate with serum IgE or age of subject.

<p>Expression of FcεRI on peripheral blood pDC was determined by flow cytometry and compared to subject's age (panel A) and serum IgE level (panel B). Data are presented as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032556#pone-0032556-g001" target="_blank">Figure 1</a>.</p

Expression of FcεRI on cDC correlates with serum IgE but not with subject's age.

<p>(A) Gating strategy used to identify expression of FcεRI and IgE on cDC and pDC. Cells were gated on scatter (R1) and lack of expression of CD19 (R2, PerCP negative). Those events that satisfied both of these criteria were examined for expression of ILT7 (R3, PE positive) versus CD1c (R4, APC positive). Cells that were CD19⁻ILT7⁺CD1c⁻ were considered pDC and CD19⁻ILT7⁻CD1c⁺ were considered cDC. The expression of FcεRI (left histograms, FITC positive) or IgE (right histograms, FITC positive) on these cells was then determined and compared to an appropriate isotype control. (B) Expression of FcεRI on peripheral blood cDC was determined by flow cytometry and compared to subject's age or (C) serum IgE level. Data are presented as fold MFI FcεRI versus age in months (B) or serum IgE in kU/L (C), with non-sensitized subjects (n = 15) in circles and sensitized subjects (n = 12) in x's. Sensitization was defined as having at least one positive allergen specific IgE by ImmunoCAP.</p