THE BIOLOGY OF AIRWAY DENDRITIC CELLS

Recent work from our laboratory has identified a network of constituti vely class II MHC (Ia) bearing dendritic cells (DC) within the epithel ium of the conducting airways of laboratory animal species and in huma ns. The density of DC within the respiratory tract is highest in those areas exposed to greater amounts of inhaled antigen and further work has identified these DC as being critically important in controlling t he induction of immune responses within the airways. The DC population in the airway epithelium is renewed every 48-72 h; this represents a more rapid turnover than DC in other tissues which are exposed to a sm aller antigenic load. In addition to these results we will discuss oth er work which shows that airway DC are a very reactive population, com parable with neutrophils in their response to acute inflammatory stimu li and that their numbers and Ia content can be modulated following ex posure to topical and systemic steroids. Finally we will discuss the d evelopment of these cells after birth and how this may influence the p athogenesis of immune regulated diseases such as asthma and allergic r hinitis.