The liver has long been recognized as important in digestion. However, the liver’s abundance of innate immune cells strongly suggests that it has specific defense mechanisms. A characteristic anatomical feature of the liver is its large blood flow. The blood flowing out from the whole alimentary tract is transported to the liver via the portal vein and distributed to peripheral structures called sinusoids. Kupffer cells, a typical example of resident macrophages, are located in sinusoids and are in continuous contact with various portal blood components. They have vigorous phagocytic activity and eliminate bacteria coming from the gut before they enter systemic circulation. Based on this framework, Kupffer cells were considered a filter for portal blood pathogens. However, recent evidence reveals that they exert crucial functions in systemic host defense against bacterial infection. To defend against various sources of bacterial pathogens, Kupffer cells construct an efficient surveillance system for systemic circulation, cooperating aggressively with other immune cells. They collaborate with non-immune cells such as hepatocytes and platelets to potentiate defense function. In conclusion, Kupffer cells coordinate immune cell activity to efficiently defend against infections, making them crucial players in systemic antibacterial immunity.
Part of the book: Antimicrobial Immune Response