The Symbiotic Defence: Lung Microbiota and The Local Immune System

Microbiota defines all microorganisms that are vital for our immunological, hormonal, and metabolic homeostasis by living symbiotically in different parts of our body. On the other hand, the microbiome is a collection of microorganisms that can be detected together. The lungs are constantly exposed to airborne microorganisms found in the upper respiratory tract. Until recently, the lower respiratory tract was considered sterile, as bacteria were rarely isolated from the lungs by conventional culture methods. Most chronic inflammatory lung diseases are caused by dysregulation of the lung microbiota, which has been discussed in many review papers. However, little is known whether microbiota dysymbiosis is a consequence or a cause of these diseases. In this review, we provide an overview of lung microbiota and lung immunity.