Dissecting the instant blood-mediated inflammatory reaction in islet xenotransplantation

Xenotransplantation. Jul-Aug 2008;15(4):225-34. doi: 10.1111/j.1399-3089.2008.00482.x.

Abstract

Background: A massive destruction of transplanted tissue occurs immediately following transplantation of pancreatic islets from pig to non-human primates. The detrimental instant blood-mediated inflammatory reaction (IBMIR), triggered by the porcine islets, is a likely explanation for this tissue loss. This reaction may also be responsible for mediating an adaptive immune response in the recipient that requires a heavy immunosuppressive regimen.

Materials and methods: Low molecular weight dextran sulfate (LMW-DS) and the complement inhibitor Compstatin were used in a combination of in vitro and in vivo studies designed to dissect the xenogeneic IBMIR in a non-human primate model of pancreatic islet transplantation. Adult porcine islets (10,000 IEQs/kg) were transplanted intraportally into three pairs of cynomolgus monkeys that had been treated with LMW-DS or heparin (control), and the effects on the IBMIR were characterized. Porcine islets were also incubated in human blood plasma in vitro to assess complement inhibition by LMW-DS and Compstatin.

Results: Morphological scoring and immunohistochemical staining revealed that the severe islet destruction and macrophage, neutrophilic granulocyte, and T-cell infiltration observed in the control (heparin-treated) animals were abrogated in the LMW-DS-treated monkeys. Both coagulation and complement activation were significantly reduced in monkeys treated with LMW-DS, but IgM and complement fragments were still found on the islet surface. This residual complement activation could be inhibited by Compstatin in vitro.

Conclusions: The xenogeneic IBMIR in this non-human primate model is characterized by an immediate binding of antibodies that triggers deleterious complement activation and a subsequent clotting reaction that leads to further complement activation. The effectiveness of LMW-DS (in vivo and in vitro) and Compstatin (in vitro) in inhibiting this IBMIR provides the basis for a protocol that can be used to abrogate the IBMIR in pig-human clinical islet transplantation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Coagulation / drug effects
  • Complement Activation / drug effects
  • Cytokines / biosynthesis
  • Dextran Sulfate / administration & dosage
  • Heparin / administration & dosage
  • Humans
  • In Vitro Techniques
  • Inflammation / blood*
  • Inflammation / etiology*
  • Islets of Langerhans Transplantation / adverse effects*
  • Islets of Langerhans Transplantation / immunology*
  • Islets of Langerhans Transplantation / pathology
  • Islets of Langerhans Transplantation / physiology
  • Macaca fascicularis
  • Peptides, Cyclic / administration & dosage
  • Sus scrofa
  • Transplantation, Heterologous

Substances

  • Cytokines
  • Peptides, Cyclic
  • compstatin
  • Heparin
  • Dextran Sulfate