Background:
The differential diagnosis of inflammatory skin diseases is largely based on the patient's history and the morphological analysis of the skin lesion. Laboratory data, such as serum IgE-level and prick and patch tests, may be helpful but do not assess individual lesions. The assumption of our approach is that each individual lesion is associated with a specific microenvironment and that the immunophenotype of the two epidermal dendritic cell populations, Langerhans cells (LC) and inflammatory dendritic epidermal cells (IDEC), reflects this environment in a disease-specific manner. Methods: A flow cytometric micromethod was developed to directly analyze individual inflammatory human skin lesions. Crude epidermal single cell suspensions were prepared by trypsinization, stained for three-color analysis with different monoclonal antibodies and the vital stain 7-amino-actinomycin-D, and finally analyzed on a single laser equipped FACScan flow cytometer. Results: With a limited set of cell surface markers, such as FcβRI, Fcβ₯RII/CD32, CD1b and CD36, highly specific diagnostic criteria for atopic dermatitis and inflamed human skin could be established. Conclusions: Phenotyping of epidermal dendritic cells is a useful procedure helpful in differential diagnosis of inflammatory skin diseases.