Injury of respiratory epithelium.

The large surface area provided by the respiratory tract epithelium of humans for exposure to microbial agents and toxic substances in the environment makes this organ system very vulnerable but a good early indicator of adverse health effects. However, the complexity of pulmonary defense mechanisms complicates definition of the interactive effects of pollutants and infectious agents. Tracheal organ culture has been utilized to maintain organized, differentiated respiratory epithelium in vitro. This model system permits the exposure of respiratory epithelium to injurious agents in an easily visualized and controlled environment. Effects of individual toxin and/or infectious agents may be examined without the involvement of most host defenses and unwanted secondary microbial invaders which hamper interpretation of in vivo model studies. Further, elements of host immune response, pharmacologic agents and the like may be added selectively if desired. A body of information is being developed on specialized respiratory cell injury by various common pathogenic agents--including respiratory syncytial virus, parainfluenza virus type 3, Bordetella pertussis and Mycoplasma pneumoniae--through studies in tracheal organ cultures. These agents injure specialized epithelial cells in different ways, providing a spectrum of changes against which the added effects of toxic substances could be evaluated at the cellular and subcellular levels. Information on the pathogenesis of infectious/toxic injury could suggest new directions for human health research and for means to benefit the human host.