| [ Summary ] |
The liver is a multi-potential organ which plays a key role in maintaining homeostasis in the human body. The liver contains many kinds of immune cells, some of which circulate in a reciprocation manner between the periphery and interior or reside in situ. A striking difference is observed in the proportion of immune cells in the liver proper and in its periphery. In the liver, the proportion of innate lymphocytes such as NK cells and NKT cells is much higher than those in the periphery. In addition, various types of antigen-presenting cells(APC)localize in the liver, most of which exert tolerogenic functions on adjacent immune cells. As representatives of professional APCs, dendritic cells and Kupffer cells induce tolerant T cells by releasing IL-10 or TGF-β. The other non-parenchymal cells, liver sinusoidal endothelial cells and hepatic stellate cells, also possess tolerance-inducing functions by producing suppressive factors or through ligation with PD-L1. These tolerogenic environments in the liver are critically involved in the pathogenesis of various liver diseases, including viral hepatitis, autoimmune liver disease or liver cancer. |