Role of Chemokine Signaling Pathways in Pancreatic Islet Rejection During Allo- and Xenotransplantation S. Sigrist, N. Ebel, A. Langlois, D. Bosco, C. Toso, C. Kleiss, K. Mandes, T. Berney, M. Pinget, A. Belcourt, and L. Kessler ABSTRACT During transplantation, pancreatic islets release chemokines promoting macrophage attrac- tion, hampering engraftment of islets. The aim of this work was to examine the mechanism of macrophage–pancreatic islets interaction that mediates islet rejection during transplantation. Human macrophages exposed to supernates of human and porcine pancreatic islets for the allogeneic and xenogeneic models, respectively, were evaluated for chemotaxis and expression of chemokine receptors (CCR-5). To modulate migration and identify the signaling pathway of macrophages, we tested pertussis toxin (PTX) to block Gi protein, and staurosporin and wortmannin to inhibit the protein kinase, and phosphoinositol-3 kinase, respectively. The addition of these agents significantly reduced macrophage migration induced by human islet supernates from 3.2  0.5 to 1.5  0.2, 0.9  0.1, and 1  0.1, respectively (P  .001, n = 3). In a xenotransplantation model, the reduction was less decreased, from 4.1  0.4 to 2.7  0.3 (P  .01), to 2.5  0.3 (P  .01), or to 1  0.1 (P  .001). Western blot analysis of chemokine receptor expression showed increased CCR-5 expression with human pancreatic islet supernates. Moreover, decreased islet purity increased CCR-5 expression. Pharmacologic study showed that PTX induced an increase in CCR-5 expression in allogeneic transplantation, whereas only staurosporin induced an increased receptor expression in the xenogeneic model, suggesting that chemokines participate in islet rejection even though the chemokine signaling pathways differ between allo- and xenotransplantation. Understanding the molecular mechanisms of islet rejection may improve graft survival. I SLET transplantation holds great promise for the treat- ment of type 1 diabetes. 1 However, islet allografts are subject to rapid rejection through host cellular immune responses involving mononuclear cell recruitment and tis- sue injury. Interruption of leukocyte recruitment through chemokine receptor targeting is of therapeutic benefit in various experimental models, 2 but little is known about the contribution of chemokine pathways to islet rejection. Chemokines are chemotactic cytokines that induce direct migration and activation of cells by binding to and activat- ing specific G-protein– coupled receptors expressed on tar- get cells. The chemokine system has been demonstrated to play an important role in guiding the migration of leuko- cytes necessary to generate an immune response as well as to deliver this response to a particular tissue site. 3 Previous studies have shown the important role of chemokine recep- tor CCR-2 in early islet allograft rejection. 4 Moreover, disruption of CCR-2 and CCR-5 signaling prolongs islet allograft survival. 5 Finally, targeting CCR-5 resulted in a significant prolongation of islet allograft survival. 6 Thus, targeting appropriate chemokine signaling pathway may provide a clinically useful strategy to prevent islet allograft and xenograft rejection. MATERIALS AND METHODS Human pancreata were retrieved from six multiorgan heart-beating donors, aged between 20 and 75 years of age, without a previous From the Laboratoire de recherche, CeeD, Strasbourg, France (S.S., N.E., A.L., C.K., M.P., A.B., L.K.); Laboratoire de transplan- tation cellulaire, Hopital cantonal de Genève, Genève, Switzer- land, (D.B., C.T., T.B.); and Laboratoire de recherche, CeeD, Strasbourg, Switzerland (K.M.). Address reprint requests to Dr Séverine Sigrist, Centre eu- ropéen d’étude du Diabète, Boulevard René Leriche, 67 200 Strasbourg, France. E-mail: ceed.sigrist@wanadoo.fr 0041-1345/05/$–see front matter © 2005 by Elsevier Inc. All rights reserved. doi:10.1016/j.transproceed.2005.09.048 360 Park Avenue South, New York, NY 10010-1710 3516 Transplantation Proceedings, 37, 3516 –3518 (2005)