MIXED CHIMERISM WITH COSTIMULATORY BLOCKADE PROLONGS ALLOGENEIC GRAFT SURVIVAL IN MURINE SMALL BOWEL TRANSPLANTATION.

Abstract

P1032 Aims: Mixed chimerism is known as one of the most powerful method to induce donor specific tolerance. Here we evaluate the potential advantage of mixed chimerism with costimulatory blockade in murine allogeneic small bowel transplantation. Methods: C57BL/6 received various combination of anti-CD8 (2.43; 1.4mg, day -2) and anti-CD154 (MR1; 2mg, day -1)mAbs with/without 3Gy total body irradiation (TBI, day -1), and 20×106 fully MHC-mismatched B10.A bone marrow cells (BMC, day -1). Heterotopic small bowel transplantation was performed on day 0 to assess induction of donor specific tolerance. Chimerism in peripheral blood was followed by FCM analysis and the frequency of TCR Vβ usage was determined by FCM to assess deletion of donor-reactive T cells. Stoma was daily observed, and acute rejection was evaluated with a microscope on POD14. Results: All animals without any treatment (n=6) showed acute rejection within 18 days after transplantation, and microscope examination presented the findings of acute rejection such as flatttend villous epithelium with the infiltration of inflammatory cells. Mice receiving anti-CD8 and anti-CD154mAbs were not induced mixed chimerism, and 4 of 8 mice rejected small bowel allograft by 79 days. All animals treated with anti-CD8mAb, anti-CD154, TBI, and BMC was induced long term multi-lineage mixed chimerism and accepted small bowel allografts (>60 days). Microscope examination presented the no findings of rejection. These chimeric animals showed specific deletion of donor reactive CD4+ peripheral blood lymphocytes (Vβ5 and Vβ11 cells). Conclusions: Prolongation of allogeneic small bowel graft survival was achieved using mixed chimerism with costimulatory blockade. Mixed chimerism with costimulatory blockade is the reliable regimen toward to the small bowel transplantation.