Yamada K, Shimizu A, Ierino F L, Utsugi R, Barth R N, Esnaola N, Colvin R B, Sachs D H
Transplantation Biology Research Center, Department of Pathology, Massachusetts General Hospital, Boston 02129, USA.
Transplantation. 1999 Dec 15;68(11):1684-92. doi: 10.1097/00007890-199912150-00011.
Previous studies in our laboratory have demonstrated the importance of the thymus for rapid and stable tolerance induction in an allotransplant model. The focus of the present study was to explore the feasibility of autologous thymic transplantation to produce a new transplantable organ (thymokidney) and to examine the function of subsequent vascularized thymokidney transplants in T cell development.
Eight juvenile swine received autologous thymic grafts under the renal capsule. Thymic tissue was obtained through a partial (n=6) or complete (n=2) thymectomy, and growth of the autologous thymic graft was compared between partially and completely thymectomized animals. Two of the partially thymectomized animals received irradiated (1000 cGy) as well as non-irradiated autologous thymic grafts. Graft survival, growth and evidence of thymocyte development was determined by (a) macroscopic examination of the implanted tissue, (b) histological examination, and (c) flow cytometry. Naive CD4 SP T cells were identified by CD45RA-expression.
Growth of transplanted thymic tissue was demonstrated in all thymic graft recipients. No difference was seen between partially and completely thymectomized animals. By POD 60, the thymic grafts exhibited normal macroscopic and microscopic structure, and normal thymocyte composition. Irradiated thymic tissue displayed a similar pattern of development, but growth was markedly delayed. To evaluate thymic function of the graft, a composite thymokidney was transplanted into a recipient which had previously been thymectomized, had few circulating CD4-single positive cells and had lost MLR reactivity. The number of CD4+/CD45RA+ cells in this animal increased steadily from POD 30 to POD 150, indicating that the thymus of the composite thymokidney allograft was functional; in addition, MLR assays demonstrated that the recipient recovered immunocompetence.
The establishment of a thymokidney by thymic autografting to the renal subcapsular space results in normal thymic growth and function, and may provide a valuable tool for studying the role of the thymus in tolerance induction. As far as we are aware, we provide the first evidence of functional vascularized thymic graft reconstituting T cells and leading to a return of a immunocompetence in a large animal model.
我们实验室之前的研究已证明胸腺在同种异体移植模型中对于快速且稳定地诱导免疫耐受具有重要意义。本研究的重点是探索自体胸腺移植以产生一个新的可移植器官（胸腺肾）的可行性，并检查后续血管化胸腺肾移植在T细胞发育中的功能。
八只幼年猪在肾被膜下接受自体胸腺移植。通过部分（n = 6）或完全（n = 2）胸腺切除术获取胸腺组织，并比较部分胸腺切除和完全胸腺切除动物中自体胸腺移植的生长情况。两只部分胸腺切除的动物接受了照射（1000 cGy）以及未照射的自体胸腺移植。通过以下方式确定移植物存活、生长及胸腺细胞发育的证据：（a）对植入组织进行宏观检查，（b）组织学检查，以及（c）流式细胞术。通过CD45RA表达鉴定初始CD4单阳性T细胞。
在所有胸腺移植受体中均证实了移植胸腺组织的生长。部分胸腺切除和完全胸腺切除的动物之间未见差异。至术后第60天，胸腺移植呈现正常的宏观和微观结构以及正常的胸腺细胞组成。照射后的胸腺组织显示出相似的发育模式，但生长明显延迟。为评估移植物的胸腺功能，将一个复合胸腺肾移植到一只先前已胸腺切除、循环中CD4单阳性细胞很少且已丧失混合淋巴细胞反应性的受体中。该动物体内CD4⁺/CD45RA⁺细胞数量从术后第30天至第150天稳步增加，表明复合胸腺肾同种异体移植物的胸腺具有功能；此外，混合淋巴细胞反应试验表明受体恢复了免疫能力。
通过将胸腺自体移植至肾被膜下间隙建立胸腺肾可实现胸腺的正常生长和功能，并且可能为研究胸腺在免疫耐受诱导中的作用提供一个有价值的工具。据我们所知，我们首次提供了在大型动物模型中功能性血管化胸腺移植物重建T细胞并导致免疫能力恢复的证据。
