Clinical use of immunopathology techniques in liver diseases

The liver is the largest organ in the human body. It synthesizes and processes essential circulating proteins, detoxifies endogenous and exogenous substances, engages in bile formation for the elimination of amphiphilic and water-insoluble molecules from the body, and constitutes a unique immunological site. Its location astride the spanchnic and systemic circulation creates a critical role for immunological processing of antigens in the splanchnic circulation. The liver anatomic structure is well suited for these biological functions, as it contains 80% of the resident macrophages in the body, Kupffer cells, and has a substantial resident population of lymphocytes and dendritic cells. The liver also has a unique ability to be subject to simultaneous damage from multiple sources, owing in part to the propensity of humans to expose themselves to infectious agents. Hepatic injury may arise from the following general causes: infectious; intrinsically immune-mediated; drug-induced (including alcohol); metabolic (including nonalcoholic fatty liver disease); mechanical (especially vascular); and environmental. The immune response, directly or indirectly, plays a crucial role in hepatocellular damage.