Demonstration of IgE low affinity Fc receptor (CD23) on normal human epidermal Langerhans cells

In previous studies, IgE molecules were detected along the cell membrane of Langerhans cells (LC) in atopic dermatitis involved skin. However, the exact nature of the receptor still remains obscure. Moreover, large subsets of leukocytes have been recently shown to express the low affinity receptor for the Fc portion of IgE (Fc epsilon RII/CD23). Since LC are epidermal leukocytes the present study was intended in order to verify if LC of normal human subjects express the Fc epsilon RII/CD23. An anti-CD23 monoclonal antibody (MoAb) was used in a double step gold immunoelectron microscopical (IEM) procedure, carried out on Ficoll-Hypaque LC-enriched epidermal cell suspensions, freshly isolated from midly trypsinized normal human skin. Cells with LC features showed gold particles on their surface. Up to now LC from normal human epidermis, investigated using MoAb against human IgE, apparently were IgE-negative. Here we inequivocally demonstrate that the Fc epsilon RII/CD23 is constitutively expressed by normal human LC. It is well known that LC play an important role in antigen presentation. Further, it has been previously described the existence of a steric relationship between CD23 and HLA-DR molecules. Therefore, the present data add further strength to the hypothesis that FC epsilon RII/CD23 could participate to antigen presentation phenomena.