The Fate of Dendritic Cells in a Mouse Model of Liver Ischemia/Reperfusion Injury P. Loi, F. Paulart, B. Pajak, N. Nagy, I. Salmon, M. Moser, M. Goldman, and V. Flamand ABSTRACT Ischemia/reperfusion during liver transplantation triggers a complex cascade of inflamma- tory events that may lead to organ dysfunction. Herein, we investigated the consequences of hepatic ischemia/reperfusion on liver dendritic cells. Liver damage was documented by increased levels of serum alanine aminotransferase and by histopathology showing large areas of hepatocyte cytolysis. MHC class II + CD45-B220 F4/80 dendritic cells were detected in necrotic areas 20 hours after reperfusion. Dendritic cells freshly isolated from reperfused livers displayed a mature phenotype characterized by upregulated expression of B7 costimulatory molecules; MHC-class II, and CD1d molecules. As shown by real-time PCR, IL-10, and TGF- mRNA accumulated in liver dendritic cells isolated after reperfusion, whereas IL-12p40 mRNA levels were decreased and IFN- mRNA levels were unchanged. These results suggest that hepatic ischemia/reperfusion results in maturation of dendritic cells, which preferentially produce inhibitory cytokines. L IVER ischemia/reperfusion (I/R) injury may cause significant hepatocellular damage and organ dysfunc- tion. The initial inflammatory reaction following reperfu- sion involves the activation of Kupffer cells, which release reactive oxygen intermediates and secrete proinflammatory mediators, including tumor necrosis factor  (TNF-), interleukin 10 (IL-10), IL-6, and IL-12. 1,2 TNF- is a central mediator of I/R inflammatory responses; it dictates the expression of adhesion molecules on vascular endothe- lial cells including  2 integrins, P- and L-selectins, 3 and ICAM-1, 4 as well as the neutrophil-attracting CXC chemo- kines IL-8 superfamily members 5 and MIP-2—which lead to neutrophil adhesion and transmigration into the liver parenchyma. 6–8 Activated neutrophils release oxidants as well as proteases and hydrolytic enzymes, which serve as the final effectors of an I/R injury. Recent studies in infectious disease models indicate that activated neutrophils also release chemotactic factors for and induce the maturation of dendritic cells (DC). 9,10 These responses, which are characterized by upregula- tion of MHC and costimulatory molecules, are required for the efficient induction of a primary immune reaction. Indeed, the DC lineage is dynamic; sequential maturational stages dictate particular functions in specific anatomic compartments. DC progenitors are found mostly in the bone marrow, from whence they migrate to peripheral tissues where they remain in an immature stage as sentinels. In the liver, interstitial DC are mostly localized in portal areas. 11 Herein, we have analyzed the fate of interstitial DC in a mouse model of liver I/R. METHODS Animals Six- to 9-week old male or female C57BL/6 mice were obtained from Harlan Netherlands (Horst, The Netherlands). Hepatic Ischemia/Reperfusion Injury Under anesthesia (Rompun 2% [xylazine 23.32 mg/mL] and Imal- ge `ne 1000 [ke ´tamine 100 mg/mL]), a laparotomy was performed on prehydrated mice. The blood supply to the left cephalic lobe of the liver was occluded for 75 minutes with an atraumatic vascular clamp. The body temperature was maintained at 37°C with a heating mattress. Reperfusion was initiated by removal of the clamps and the wound was closed in layers with 3-0 silk. From the Institute for Medical Immunology—Laboratory of Experimental Immunology (P.L., F.P., M.G., V.F.), IBMM (B.P., M.M.), and Ho ˆ pital Erasme (P.L., F.P., N.N., I.S., M.G., V.F), Universite Libre de Bruxelles, Brussels. Supported by the FNRS and the Politique Scientifique Fe ´ de ´- rale (Belgium). V.F. is a research fellow of the F.N.R.S. P.L. is supported by the Erasme Foundation. Address reprint requests to V. Flamand, ULB-Campus Erasme; 808 route de Lennik, B-1070 E-mail: vflamand@ulb. ac.be © 2004 by Elsevier Inc. All rights reserved. 0041-1345/04/$–see front matter 360 Park Avenue South, New York, NY 10010-1710 doi:10.1016/j.transproceed.2004.05.052 Transplantation Proceedings, 36, 1275–1279 (2004) 1275