Kupffer Cell-Mediated Lymphocyte Apoptosis: A PGE2-Dependent Mechanism of Portal Venous Transfusion-Induced Immunosuppression?

Abstract

Background.Kupffer cells, after exposure to alloantigen via the portal vein, mediate an immunosuppressive effect involving enhanced production of PGE2. We hypothesize that up-regulation of Kupffer cell CoA-independent transacylase (CoA-IT) by portal venous transfusion (PVT) is a possible mechanism of increased PGE2production. Additionally, enhanced lymphocyte apoptosis, a process known to be macrophage dependent and facilitated by PGE2, is postulated as a possible mechanism of PVT-induced, Kupffer cell-mediated immunosuppression.Methods.Lewis rat Kupffer cells were isolated after portal venous infusion with 1 ml of Wistar–Firth blood (PVT) or saline (PV sal). Kupffer cell PGE2production and CoA-IT activity was assessed. Lymphocyte apoptosis after exposure to PVT or PV sal-treated Kupffer cells was also assessed by flow cytometry.Results.PVT-treated Kupffer cells produced significantly more PGE2and had increased CoA-IT activity when compared to PV sal-treated Kupffer cells. Treatment of Kupffer cells with a selective inhibitor of CoA-IT significantly decreased PVT-induced Kupffer cell PGE2production. Increased lymphocyte apoptosis was observed after coculture with PVT-treated Kupffer cells compared to PV sal-treated cells.Conclusions.PVT increases Kupffer cell PGE2production via increased CoA-IT activity and induces Kupffer cell-mediated lymphocyte apoptosis. Lymphocyte apoptosis facilitated by Kupffer cells within the hepatic sinusoid may be an important mechanism of PVT-induced immunosuppression in organ transplantation.