Immunoglobulins and their receptors on epidermal Langerhans cells in atopic dermatitis

To elucidate the etiological role of immunoglobulin molecules on Langerhans cells (LCs) in atopic dermatitis, we conducted immuno-histochemical studies on the localization of immunoglobulin G1 (IgG1), IgG2, IgG3, IgG4, IgA and IgM on epidermal LCs from 30 patients with atopic dermatitis (AD) and five non-atopic healthy volunteers. We also investigated the types of receptors for the immunoglobulins (Fc epsilon RI, Fc epsilon RII, Fc gamma RI, Fc gamma RII, and Fc gamma RIII) on epidermal LCs in the patients. IgE positive epidermal LCs were observed in 28 of 30 AD patients, and 46.7% of the epidermal LCs were positive for IgE. Both IgG1- and IgG2-positive epidermal LCs were observed in 70% of AD patients, and 21.8% and 28.7% of the total epidermal LCs were positive for IgG1 and IgG2, respectively. IgG3- or IgG4-positive LCs were present in only small proportions of AD patients. IgA-positive LCs were observed in 8 AD patients; our study suggested that the IgA bound on LCs was secretory IgA (S-IgA). These surface immunoglobulins were observed significantly more frequently on epidermal LCs in the involved skin of AD than in clinically uninvolved skin. No IgM-positive epidermal LCs were observed in the AD patients or healthy volunteers. In non-atopic healthy controls, no immunoglobulin-binding LCs were observed. In receptors for immunoglobulins, Fc epsilon RI and Fc gamma RII were exclusively expressed on nearly all epidermal LCs from all AD patients and all non-atopic controls. These results suggested that not only IgE but also IgG and IgA may play some etiological role in the pathogenesis of AD.