Allergen uptake and presentation by dendritic cells.

Allergic diseases such as atopic dermatitis, rhinitis and asthma are thought to result from a dysregulated immune response to commonly encountered antigens in genetically predisposed individuals. This response leads to chronic eosinophil-rich allergic inflammation and is controlled by Th2 lymphocytes. The first step in the allergic immune response is the uptake and presentation of allergen by professional antigen presenting cells such as dendritic cells, macrophages and B lymphocytes. Immature dendritic cells reside in the epithelia of the skin, upper and lower airways and gut and have the potential to sense foreign antigens and non-specific inflammatory tissue damage. Following recognition and uptake of Ag, mature dendritic cells migrate to the T-cell rich area of draining lymph nodes, display an array of Ag-derived peptides on the surface of major histocompatibility complex molecules and acquire the cellular specialization to select and activate naive Ag-specific T cells. By the nature of the signals they provide to naive T cells, mature dendritic cells are critical for polarizing Th0 helper cells into either Th1 or Th2 effector cells and for inducing long-lived memory Th cells. This article reviews recent information implying dendritic cells in the pathogenesis of allergic disease.