Delayed type hypersensitivity-associated cytokines in islet xenotransplantation:: limited efficacy of interleukin-2-and tumor necrosis factor-α-blockade in interferon-γ receptor-deficient mice

To investigate the role of interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha and their potential to replace each other in the process of fetal porcine islet-like cell cluster (ICC) xenograft rejection, mice with a targeted disruption of the IFN-gamma receptor gene and wild-type controls were transplanted with fetal porcine ICCs under the kidney capsule and given post-transplant treatment with the TNF-oc-inhibiting agent MDL 201,449A. Some of the MDL 201,449A-treated IFN-gamma receptor-deficient mice received additional treatment with cyclosporinee (CsA). Evaluation of the xenografts was performed 7 days after transplantation (all groups), and in IFN-gamma receptor-deficient mice treated with MDL 201 449 A, also 10 and 13 days after transplantation. On day 7 after transplantation, a few CD3(+) cells were seen accumulated peripherally in the ICC xenograft. Moderate to abundant numbers of F4/80(+) and Mac-1(+) cells surrounded a few remaining ICCs present within the xenograft. Histochemical visualization of cyanide-resistant endogenous peroxidase activity for detection of eosinophils demonstrated only small numbers of eosinophils present within the xenograft by day 7 after transplantation. An increased amount of eosinophilic granulocytes was not found until day 10 after transplantation, i.e. at a time when ICC xenograft rejection has already been completed. However, two out of six IFN-gamma receptor-deficient mice given post-transplant treatment with CsA and MDL 201,449A exhibited intact ICC xenografts with ICCs arranged in chords and duct-like structures on day 7 after transplantation. Taken together, findings in this study indicate that, in the pig-to-mouse model, IFN-gamma, TNF-alpha, and interleukin-2 seem to be of importance to fetal porcine ICC xenograft rejection. Nevertheless, in a majority of animals, other cytokines eventually substitute for the lack of IFN-gamma, TNF-alpha and interleukin-2.