Regulation of T helper cell differentiation by respiratory tract dendriticcells

Studies on dendritic cells (DC) of the respiratory and gastric mucosae have identified an extensive network of cells that represent the predominant an tigen-presenting cell type at these sites. Under steady-state conditions, r espiratory tract DC (RTDC) are specialized for antigen uptake and spontaneo usly migrate to local lymph nodes, although in vitro transfer studies have shown that the T-cell priming activity of these cells is restricted to low- level, Th2-skewed responses. Following exposure to inflammatory stimuli, th e migration of RTDC to lymph nodes is accelerated and is associated with a rapid and dramatic increase in the ability of these cells to induce both Th 1- and Th2-dependent immunity. Under normal circumstances, however, respons iveness of epithelial RTDC to maturation stimuli is regulated by locally pr oduced micro-environmental factors, including pro-inflammatory cytokines, r eactive oxygen species and prostanoids. These studies have led to a greater understanding of airway DC function and their role in T helper cell differ entiation and provide the basis for future studies to determine the role of the cells in the aetiology and pathogenesis of respiratory immunoinflammat ory disorders.