MODULATION OF AIRWAY INTRAEPITHELIAL DENDRITIC CELLS FOLLOWING EXPOSURE TO STEROIDS

Recent studies from our laboratory have identified a network of consti tutively class [I major histocompatibility complex (MHC) (la)-bearing dendritic cells (DC) within the epithelium of the conducting airways o f laboratory animal species and in humans. These studies have also dem onstrated that the density of the DC network increases within the airw ay epithelium in response to inflammatory challenge. In the present re port, we demonstrate that exposure of adult rats to inhaled steroids r eads to a rapid but readily reversible decrease both in the number of airway intraepithelial DC, and in their surface la expression. Similar changes are also seen in response to high doses of systemic dexametha sone. In addition, we demonstrate that steroid inhalation reduces the rate of postnatal expansion of the airway intraepithelial DC network i n rat pups, and prevents the rapid expansion of the DC network in adul ts which occurs during the acute inflammatory response following inhal ation of microbial stimuli.