Treatment with Anti-FcεRIα (MAR-1) Antibody Prevents Acute Islet Allograft Rejection in a Murine Model

Objective: Various immunological strategies for tolerance induction against allogeneic tissue grafts (allografts) have been tested in islet transplant recipients; for example, T cell activating co-stimulatory pathway blockade has been shown to prolong islet allograft survival. However, little is known about whether infiltrating inflammatory cells (e.g., basophils) affect islet allograft fates before antigen-specific immune cell development. Herein, we treated mice with a basophil-specific monoclonal antibody (mAb) and examined whether early acute-phase islet allograft rejection could be prevented in recipients. Methods: Pancreatic islets isolated from C57BL/6 (H-2b) or DBA/2 (H-2d) mice were transplanted under the renal capsules of C57BL/6 recipient mice. Recipients receiving allografts were administered the anti-basophil mAb MAR-1 to examine the antibody-mediated effect on graft survival. At days 4 and 7 post-transplantation, graft-bearing recipient kidneys were harvested for immunohistological analysis and stained with anti-insulin antibody to compare the sizes of grafted islets. Results: On day 7 post-transplantation, the transplanted pancreatic islet clusters in allograft-recipient kidneys had rapidly decreased in size, whereas those in syngeneic recipients remained larger in both size and number. However, MAR-1-treated recipients had increased the numbers of larger insulin-positive allograft islet cell clusters. Conclusion: Basophil-specific mAb treatment contributes to enhance and prolong transplanted islet survival in allogeneic recipient mice.