Fig. 1. Dynamic connections of microbiome inhabiting different human body sites.

Oral, lung, and gut microbiome could communicate with each other via direct manner including mucosal dispersion, respiratory and digestive activities, and indirect manner via inflammatory substances, cytokine, and metabolites in systematic circulation. Bacteria and its metabolites from intestinal tract modulate the differentiation tendency of naive T cells and Th17 release, modulating the systematic inflammation and immunity.