[IgE receptors in Langerhans cells. A link between the environment and the immune system?]

The demonstration of IgE-bearing epidermal Langerhans cells (LC) opened up new perspectives in the pathophysiology of atopic eczema. IgE receptors on LC have now been identified and characterized: all three IgE-binding structures so far known to be present in the human immune system have been demonstrated on LC, i.e. the low-affinity receptor for IgE (Fc epsilon RII/CD23), the so-called IgE-binding protein (epsilon BP) and the high-affinity receptor for IgE (Fc epsilon RI), which had hitherto been considered to be expressed exclusively on mast cells and basophils. Functionally, there is some evidence that these structures may be involved in the release of cytokines and/or IgE-mediated antigen focusing. Considering the specificity of IgE for environmental allergens and the particular place of LC in primary and secondary immune responses, it can be speculated that LC in the skin and mucosae play a major role in mechanisms of sensitization to such allergens and in the genesis of IgE-mediated diseases. Finally, IgE receptors on LC may provide targets for new therapeutic approaches in atopic diathesis.