DENDRITIC CELLS ARE RECRUITED INTO THE AIRWAY EPITHELIUM DURING THE INFLAMMATORY RESPONSE TO A BROAD-SPECTRUM OF STIMULI

A key rate-limiting step in the adaptive immune response at peripheral challenge sites is the transmission of antigen signals to T cells in regional lymph nodes. Recent evidence suggests that specialized dendri tic cells (DC) fulfill this surveillance function in the resting state , but their relatively slow turnover in most peripheral tissues brings into question their effectiveness in signaling the arrival of highly pathogenic sources of antigen which require immediate mobilization of the full range of host defenses for maintenance of homeostasis. Howeve r, the present report demonstrates that recruitment of a wave of DC in to the respiratory tract mucosa is a universal feature of the acute ce llular response to local challenge with bacterial, viral, and soluble protein antigens. Consistent with this finding, we also demonstrate th at freshly isolated respiratory mucosal DC respond in vitro to a varie ty of CC chemokines as well as complementary cleavage products and N-f ormyl-methionyl-leucine-phenylalanine. This suggests that rapid amplif ication of specific antigen surveillance at peripheral challenge sites is an integral feature of the innate immune response at mucosal surfa ces, and serves as an ''early warning system'' to alert the adaptive i mmune system to incoming pathogens.