Characteristics of pre-sensitization-related acute antibody-mediated rejection in a rat model of orthotopic liver transplantation

BACKGROUND: To establish an animal model of pre-sensitization following liver transplantation either with or without immunosuppressors. To study whether accelerated liver rejection or acute antibody-mediated rejection (AMR) occurred and study the characteristics and potential mechanism in the animal model. METHODS: Lewis (LEW) rats were subjected to liver [liver graft of Brown Norway (BN) rat] transplantation 2 weeks after lymphocyte injection (lymphocytes of BN rat; pre-sensitization). At 2 weeks after transplantation, serum samples of recipients were collected for antibody analysis to identify donor-specific alloantibody (DSA) level. The recipients were treated with or without a low dose of immunosuppressor (2 mg/kg). The liver grafts of each group were analyzed by hematoxylin and eosin (HE) stain, Masson stain, CK19, C4d, and CD20 immunohistochemical (IHC) stain, CD3, CD68, and CD86 immunofluorescence and transmission electron microscope (TEM) to study the characteristics of liver rejection. Moreover, cytotoxin-associated genes, M1 macrophages conversion-related proteins, and interleukin-6 (IL-6) signaling pathway proteins were detected by western blotting. RESULTS: High level of DSA and accelerated liver rejection occurred in the pre-sensitized rat models following liver transplant. Accelerated liver graft rejection occurred in the pre-sensitized, post liver transplant rats regardless of whether a low dose immunosuppressor had been applied. Severe injury of the interlobular bile ducts and accelerated fibrosis could be observed. Moreover, evidence of endothelial injury, such as capillary inflammation, was found in the pre-sensitized, post-transplant rats. In addition, C4d deposition and M1 macrophages recruitment were also found in this sensitized followed transplant model, indicating that complement activation might occur in this model. The levels of IL-6, JAK1, STAT3, SHP2, and ERK1-2 were increased in the pre-sensitized, post-transplant rats. CONCLUSIONS: Pre-sensitized post liver transplant rats might be potential AMR models for further study.