The Langerhans cell: an underestimated cell in atopic disease.

Langerhans cells (LC) are very potent antigen-presenting cells. In atopic disorders such as allergic rhinitis and atopic dermatitis LC are known to bear IgE surface molecules. IgE-positive LC can bind allergen and present it to T lymphocytes to induce an allergen-specific T-cell response and IgE synthesis. Therefore, IgE-bearing LC might play an important role in the triggering of the immune system to maintain ongoing IgE synthesis. The importance of the IgE-bearing LC in atopy has not been assessed but deserves further investigation to find out more about the part played by these cells, not only in the atopic disorders described here but also in others such as gastrointestinal allergy and allergic asthma.