Current concepts in cell-mediated hepatic allograft rejection leading to ductopenia and liver failure

Hepatic allograft rejection is presently classified into acute and chronic rejection based on histological features, timing and reversibility. However, because features of both types of rejection can occur at any time, and in many combinations, the terms "acute" and "chronic" seem inappropriate in some instances. Thus the term "cellular rejection" better defines the histological features of portal hepatitis, nonsuppurative destructive cholangitis and endotheliitis, which are independent of time and response to therapy. Similarly, because progressive bile duct destruction leading to a decrease in the number of interlobular and septal bile ducts is the major histological feature of "chronic rejection," the term "ductopenic rejection," defined as the loss of bile ducts in 50% or more of portal tracts independent of time and reversibility, seems more appropriate. The pathogenesis of cell-mediated rejection has not been completely explained; however, direct immunocytic attack on small bile ducts and small arteries appear to be the major feature. The process may lead to bile duct loss ("ductopenia"). The pathogenetic role of foam-cell arteritis resulting in ischemic bile duct injury and the role of humoral mechanisms in causing ductopenic rejection awaits further clarification. In the past, irreversible ductopenic rejection occurred in approximately 10% of all patients who underwent their first liver transplantation; this figure, however, appears to be decreasing. The clinical features of irreversible rejection include persistent and progressive cholestasis; rising serum levels of bilirubin, alkaline phosphatase and gamma-glutamyltransferase; and a decrease in hepatic synthetic function. Ductopenic rejection can occur early (2 to 5 wk after liver transplantation) but most often develops between 6 wk and 6 mo after transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)