Chronic antibody-mediated responses may mediate chronic rejection in rat orthotopic liver transplantation

The category of chronic antibody-mediated rejection (AMR) is not included in Banff schema for liver allograft rejection. In the present study, we examined the pathology of chronic rejection using rat liver transplantation. Orthotopic liver transplantation from Lewis to BN rats was performed without immunosuppression, and with or without HA reconstruction. We studied grafts at day 120 for arterialized and day 39 for nonarterialized transplants focusing on the immunoglobulin G (IgG) deposition and the pathologic characteristics of rejection. About 20% of arterialized grafts survived more than 120 days. Between day 7 and day 120, T-cell infiltration to arterialized grafts was accompanied by IgG deposition in portal veins, hepatic arteries, and bile ducts in portal areas, sinusoids and hepatocytes. At day 120, arterialized grafts were morphologically characterized by late chronic rejection with IgG deposition, intraluminal portal veins fibrosis, intimal fibrous thickening of hepatic arteries, diffuse sinusoidal fibrosis, as well as injury and loss of bile ducts due to fibrosis. The severities of T cell-mediated rejection and AMR were higher in nonarterialized than arterialized grafts. Nonarterialized Lewis liver grafts in BN rats were rejected by day 39, as characterized by late chronic rejection with IgG deposition and cellular infiltration. In conclusion, chronic AMR may be involved in chronic rejection of liver transplantations. When chronic AMR was involved in chronic liver graft rejection, typical late morphological changes emerged within a short period.