Luo Bin, Nanji Sulaiman A, Schur Colleen D, Pawlick Rena L, Anderson Colin C, Shapiro A M James
Surgical Medical Research Institute, Department of Surgery, University of Alberta, Canada.
Transplantation. 2005 Aug 15;80(3):370-7. doi: 10.1097/01.tp.0000167724.38038.ae.
Whether mixed chimeras induced by nonmyeloablative conditioning are tolerant to challenge with donor allogeneic islet grafts is unknown. Here we investigate whether our nonmyeloablative, costimulation blockade-free and sirolimus (SRL)-based protocol could facilitate mixed chimerism via bone marrow transplantation (BMT) and induce islet allograft tolerance.
After low dose (1-3 Gy) total body irradiation (TBI, day -1), with or without prior lymphocyte depletion, C57BL/6 mice were transfused with 40 x 10(6) BALB/c bone marrow cells (day 0) and received SRL (3 mg/kg/day) for 4 weeks. Chimerism was monitored by flow cytometry and the recipients were rendered diabetic chemically and challenged with donor islets.
Mixed chimerism was achieved in mice treated with TBI 3 Gy/SRL but it declined over time in 60% (9/15) of them. Long-term stable chimerism was established in 100% of recipients over 50 weeks with either antilymphocyte serum (ALS, 9/9), anti-CD4 (4/4), or anti-CD4 plus anti-CD8 (5/5) prior to BMT. TBI conditioning could be reduced to 1 Gy, with 90% (9/10) maintaining chimerism in the long-term. When TBI was substituted with cyclophosphamide (CTX) or busulfan (BUS), all mice remained chimeric in the long-term. The chimeras showed no proliferative response to donor antigen and accepted both first and second donor-specific islet grafts indefinitely while rejecting third-party grafts.
This data provides the first evidence that stable fully allogeneic chimeras induced with BMT after nonmyeloablative conditioning with SRL and lymphocyte-depleting antibodies exhibit robust donor-specific tolerance to islet grafts.
非清髓性预处理诱导的混合嵌合体是否对供体同种异体胰岛移植的挑战具有耐受性尚不清楚。在此，我们研究我们基于非清髓性、无共刺激阻断且使用西罗莫司（SRL）的方案是否能通过骨髓移植（BMT）促进混合嵌合，并诱导胰岛移植耐受。
在低剂量（1 - 3 Gy）全身照射（TBI，第 -1 天）后，无论有无预先淋巴细胞清除，C57BL/6 小鼠于第 0 天输注 40×10⁶ BALB/c 骨髓细胞，并接受 SRL（3 mg/kg/天）治疗 4 周。通过流式细胞术监测嵌合情况，受体通过化学方法诱导糖尿病并接受供体胰岛的挑战。
接受 3 Gy TBI/SRL 治疗的小鼠实现了混合嵌合，但其中 60%（9/15）的小鼠嵌合率随时间下降。在 BMT 前使用抗淋巴细胞血清（ALS，9/9）、抗 CD4（4/4）或抗 CD4 加抗 CD8（5/5）的情况下，100%的受体在超过 50 周的时间里建立了长期稳定的嵌合。TBI 预处理剂量可降至 1 Gy，90%（9/10）的小鼠长期维持嵌合。当用环磷酰胺（CTX）或白消安（BUS）替代 TBI 时，所有小鼠长期保持嵌合。嵌合体对供体抗原无增殖反应，无限期接受首次和第二次供体特异性胰岛移植，同时排斥第三方移植。
该数据首次证明，在使用 SRL 和淋巴细胞清除抗体进行非清髓性预处理后通过 BMT 诱导的稳定完全同种异体嵌合体对胰岛移植表现出强大的供体特异性耐受。
