The gut–airway microbiome axis in health and respiratory diseases

Communication between the gut and remote organs, such as the brain or the cardiovascular system, has been well established and recent studies provide evidence for a potential bidirectional gut–airway axis. Observations from animal and human studies indicate that respiratory insults influence the activity of the gut microbiome and that microbial ligands and metabolic products generated by the gut microbiome shape respiratory immunity. Information exchange between these two large mucosal surface areas regulates microorganism–immune interactions, with significant implications for the clinical and treatment outcomes of a range of respiratory conditions, including asthma, chronic obstructive pulmonary disease and lung cancer. In this Review, we summarize the most recent data in this field, offering insights into mechanisms of gut–airway crosstalk across spatial and temporal gradients and their relevance for respiratory health.