Biotin
Epidermal Langerhans cells (LCs) and the high-affinity receptor for IgE (Fc(epsilon)RI) on their surface are considered important in the pathogenesis of atopic dermatitis (AD). We investigated the numbers of epidermal LCs and their Fc(epsilon)RI expression in patients with AD and healthy controls. Biopsy specimens taken from lesional skin from 17 patients with AD, non-lesional skin from five patients with AD and normal skin from five healthy individuals were immunohistochemically stained with a monoclonal antibody against CD1a or with either of two monoclonal antibodies against two different epitopes of Fc(epsilon)RI alpha chain. Many dendritic cells were positively stained with anti-CD1a antibody in the epidermis of each skin sample, and fewer cells were stained with anti-Fc(epsilon)RI antibodies. The numbers of epidermal LCs positive for Fc(epsilon)RI were significantly increased in both lesional and non-lesional skin from AD patients compared with those in normal skin, suggesting important roles of Fc(epsilon)RI+LCs in the pathogenesis of the disease. In contrast, the numbers of total epidermal LCs (CD1a-positive) were decreased in AD lesional skin compared with those in non-lesional skin from AD patients and in normal skin from healthy subjects. Together with our finding that the numbers of epidermal LCs were negatively correlated with the clinical severity of the AD lesions, we concluded that epidermal LCs may decrease in some conditions of AD, probably in lesions with severe inflammation.
The extracellular portion of the alpha chain of the human high-affinity IgE receptor (FcepsilonRIalpha) was expressed as inclusion bodies in Escherichia coli. In immunoblot analysis, two bands were reactive to human IgE and mouse anti-human FcepsilonRIalpha monoclonal antibodies. N-terminal sequencing showed that the two bands were equivalent to the soluble FcepsilonRIalpha with a methionine residue at the N-terminus (Met-1-172) and 23-172, in which the N-terminal 22 residues of the soluble FcepsilonRIalpha have been removed, possibly by degradation in E. coli cells. IgE-binding to CHO cells expressing FcepsilonRI was inhibited by the addition of the recombinant products prepared by the refolding procedure from inclusion bodies. The system for the expression of soluble human FcepsilonRIalpha in E. coli presented in this study and its further improvement would be useful for the production of the protein as a potent therapeutic and for analysis of the IgE-FcepsilonRIalpha interaction.
