Revisiting the liver’s role in transplant alloimmunity

Figure 2 Liver architecture and resident immune cells. A: The liver’s unique architecture and the large number of passenger immune cells that accompany it during transplant likely play a role in its immunologic activity. Class I major histocompatibility (MHC) antigens are strongly expressed on bile ducts (c) and to a lesser extent on sinusoidal and endothelial cells (g). By contrast, Class II MHC antigens are primarily expressed on capillary endothelium, sinusoidal cells and dendritic cells (f). It is also recognized that cell surface MHC antigens are not static and can change in response to host and allograft dynamics such as infection and rejection; B: Liver transplants secrete soluble class I MHC antigens that bind and neutralize systemically circulating antibodies. Kupffer cells (d) also are involved in neutralization of antibodies. As such, liver allografts are thought to function as sinks for circulating immune complexes. EC: Endothelial cell; NK: Natural killer; MHC: Major histocompatibility complex.