The Lung Microbiome, Immunity, and the Pathogenesis of Chronic Lung Disease.

The development of culture-independent techniques for microbiological analysis has uncovered the previously unappreciated complexity of the bacterial microbiome at various anatomic sites. The microbiome of the lung has relatively less bacterial biomass when compared with the lower gastrointestinal tract yet displays considerable diversity. The composition of the lung microbiome is determined by elimination, immigration, and relative growth within its communities. Chronic lung disease alters these factors. Many forms of chronic lung disease demonstrate exacerbations that drive disease progression and are poorly understood. Mounting evidence supports ways in which microbiota dysbiosis can influence host defense and immunity, and in turn may contribute to disease exacerbations. Thus, the key to understanding the pathogenesis of chronic lung disease may reside in deciphering the complex interactions between the host, pathogen, and resident microbiota during stable disease and exacerbations. In this brief review we discuss new insights into these labyrinthine relationships.