People are an organic unity: Gut-lung axis and pneumonia

People are an organic unity. Every organ of our body doesn 't exist alone. They are a part of our body and have important connections with other tissues or organs. The gut -lung axis is a typical example. Here, we reviewed the current research progress of the gut -lung axis. The main cross between the intestine and lungs was sorted out, i.e. the specific interaction content contained in the gut -lung axis. We determine a relatively concept for the gut -lung axis, that is, the gut -lung axis is a cross -talk that the gut and lungs interact with each other through microorganisms and immune system to achieve bidirectional regulation. The gut and lungs communicate with each other mainly through the immune system symbiotic microbes, and these two pathways influence each other. The portal vein system and mesenteric lymphatics are the primary communication channels between the intestine and lungs. We also summarized the effects of pneumonia, including Coronavirus disease 2019 (COVID-19) Community -Acquired Pneumonia (CAP), on intestinal microbes and immune function through the gut -lung axis, and discussed the mechanism this effect. Finally, we explored the value of intestinal microbes and the gut -lung axis in the treatment of pneumonia through the effect of intestinal microbes on pneumonia.