Abstract
The human gastrointestinal tract is the largest immune organ in the body and consequently influences the overall immune state of all body sites. The gut also harbors the largest proportion of the microbiome. In early life, the maturation of the microbiome and immune system are closely entangled, forming a homeostatic system that imparts individuality and stability to the host microbiome. It is now well established that factors that affect early life gut microbiota modulate susceptibility to chronic inflammatory diseases, including airway diseases such as asthma and allergy. Despite this global influence of the gut on immune response in the lungs, local microbiome-immune interactions also shape the response and susceptibility to disease in the airways. The upper respiratory tract and lung microbiomes also contribute to acute and chronic airway diseases. Modulating the gut-lung axis as well as respiratory tract through microbiome-targeted interventions to promote health and reduce susceptibility to infection and chronic inflammatory disease may represent an effective strategy, particularly in early and late life.