Atopic dermatitis patients have increased numbers of FcɛRIα and IgE double positive monocytes and plasmacytoid dendritic cells in peripheral blood mononuclear cells

Abstract Antigen presenting cells including monocytes and dendritic cells have been reported to express cell surface high-affinity IgE receptor (FcɛRI) and binds to IgE. However, the frequencies of these cells in human peripheral blood mononuclear cells (PBMCs) are ambiguous, and the biological function of these cells in human remains to be characterized. In this study, we investigated the frequencies of cell surface expression of FcɛRIα and cell surface bound IgE in PBMCs isolated from normal human controls (NC) and atopic dermatitis (AD) patients using multicolor flow cytometry methods. While the frequencies of FcɛRIα+ single positive cells have no significant differences between NC and AD, we found that the frequencies of FcɛRIα and surface-bound IgE double positive cells (FcɛRIα+IgE+) in human PBMCs are significantly increased in AD patients (mean ±SD: 2.52% ± 1.33%) compared to NC (mean ±SD: 1.26% ± 0.79%) (p=0.003). In addition, the frequencies of FcɛRIα+IgE+ cells are positively correlated with serum IgE levels (Spearman analysis: r=0.67, p<0.0001). The FcεRIα+IgE+ cells in both NC and AD subjects are comprised of monocytes, conventional DCs (cDCs) and plasmacytoid DCs (pDCs). While the numbers of FcεRIα+IgE+ cDCs have no significant difference between NC and AD, FcɛRIα+IgE+ monocytes and pDCs are significantly increased in AD patients compared to NC subjects. Collectively, our study identified a distinct FcɛRIα+IgE+ cell population in human PBMCs, and this population is increased in AD. Further investigation is warranted to characterize the biological significance of this particular cell population in normal humans and AD patients. Supported by grants from Genentech (ML41620)