The FcϵRIγ chain in the dendritic cells of atopic and nonatopic donors

Abstract

The high-affinity IgE receptor (FcϵRI) is absent or weakly expressed on the antigen-presenting dendritic cells (DCs) of nonatopic individuals but is strongly expressed on the DCs of atopic individuals. In this study, it was found that the intracellular α chain of the FcϵRI (FcϵRIα) accumulates during DC differentiation from monocytes in almost all individuals. In most atopic individuals, there is a strong intracellular expression of the γ chains of the FcϵRI (FcϵRIγ) in their DCs, which exhibit prominent FcϵRI expression on the surface. This FcϵRIγ can be co-precipitated with FcϵRIα. However, in those nonatopic individuals with little expression of FcϵRI on the surface of DCs, there is downregulation of the expression of the FcϵRIγ, a component found to be mandatory for surface expression of FcϵRI. In such DCs with downregulated FcϵRIγ, there is an accumulation of an immature and core-glycosylated FcϵRIα chain in the endoplasmic reticulum. In contrast, DCs that express ample FcϵRIγ contain an additional mature form of FcϵRIα exhibiting a complex glycosylation pattern that co-localizes with FcϵRIγ in the Golgi compartment. These findings suggest that the expression of FcϵRIγ plays an important role in the expression of the FcϵRIα chain on the surface of the DC, where it can bind IgE. Furthermore, the authors present evidence that the increased levels of IgE present in most atopic individuals help to sustain surface-expressed FcϵRI on DCs. The high-affinity IgE receptor (FcϵRI) is absent or weakly expressed on the antigen-presenting dendritic cells (DCs) of nonatopic individuals but is strongly expressed on the DCs of atopic individuals. In this study, it was found that the intracellular α chain of the FcϵRI (FcϵRIα) accumulates during DC differentiation from monocytes in almost all individuals. In most atopic individuals, there is a strong intracellular expression of the γ chains of the FcϵRI (FcϵRIγ) in their DCs, which exhibit prominent FcϵRI expression on the surface. This FcϵRIγ can be co-precipitated with FcϵRIα. However, in those nonatopic individuals with little expression of FcϵRI on the surface of DCs, there is downregulation of the expression of the FcϵRIγ, a component found to be mandatory for surface expression of FcϵRI. In such DCs with downregulated FcϵRIγ, there is an accumulation of an immature and core-glycosylated FcϵRIα chain in the endoplasmic reticulum. In contrast, DCs that express ample FcϵRIγ contain an additional mature form of FcϵRIα exhibiting a complex glycosylation pattern that co-localizes with FcϵRIγ in the Golgi compartment. These findings suggest that the expression of FcϵRIγ plays an important role in the expression of the FcϵRIα chain on the surface of the DC, where it can bind IgE. Furthermore, the authors present evidence that the increased levels of IgE present in most atopic individuals help to sustain surface-expressed FcϵRI on DCs.