Latinne D, Vitiello D M, Sachs D H, Sykes M
Transplantation Biology Research Center, Surgical Service, Massachusetts General Hospital, Boston 02129.
Transplantation. 1994 Jan;57(2):238-45.
Xenotransplantation could potentially overcome the organ shortage that currently limits the field of transplantation. Because of their breeding characteristics as well as their size and physiologic similarities to humans, we have chosen miniature swine as possible xenograft donors, and are currently attempting to develop a means of using mixed xenogeneic chimerism as an approach to tolerance induction in swine-to-primate species combinations. One major barrier to organ grafting from pig to man is the presence in human serum of preformed natural antibodies (NAb) reacting with antigens expressed on porcine endothelial cells and causing hyperacute rejection. Previous experiments performed in our laboratory have shown that both humoral and cellular tolerance can be induced in a concordant xenogeneic species combination (rat-->mouse) using donor bone marrow infusion following conditioning with a nonmyeloablative regimen. Induction of chimerism in these animals was associated with a marked reduction in the level of IgM natural antibodies that recognize rat bone marrow cells. A similar approach could also lead to humoral and cellular tolerance induction in the swine-->human species combination, permitting transplantation of vascularized organs from the swine donor. To determine the potential of bone marrow transplantation to induce a state of "natural antibody tolerance," it was essential to determine whether or not all human NAb target antigens expressed on swine EC are also expressed on cells derived from swine bone marrow. We have addressed this question by evaluating the ability of various swine bone marrow-derived cells to absorb human IgM and IgG NAb that bind to swine EC. Our results demonstrate that swine bone marrow cells and their progeny can absorb almost all IgM NAb that bind to swine EC, as detected by flow cytometric and ELISA assays. Specificity of absorption was demonstrated, as total serum IgM levels declined only minimally after absorption on swine BMC and to an extent comparable to that observed following absorption with human cells, which did not deplete swine EC-binding NAb. Human IgG binding to swine EC was also completely absorbed by swine BMC. These results suggest that a state of "NAb tolerance" could be induced by successful swine marrow engraftment in man. Furthermore, swine PBL, platelets, and EC were able to absorb most IgM NAb that bound to swine BMC, suggesting that absorption using antigen from any of these tissues might facilitate marrow engraftment, and hence tolerance induction, in this species combination.
异种移植有可能克服目前限制移植领域发展的器官短缺问题。鉴于小型猪的繁殖特性以及其大小和生理特征与人类的相似性，我们选择小型猪作为可能的异种移植供体，目前正试图开发一种利用混合异种嵌合体的方法，在猪到灵长类动物的物种组合中诱导耐受性。猪到人的器官移植的一个主要障碍是人类血清中存在预先形成的天然抗体（NAb），这些抗体与猪内皮细胞上表达的抗原发生反应，导致超急性排斥反应。我们实验室之前进行的实验表明，在采用非清髓性方案预处理后，通过输注供体骨髓，可以在一致的异种物种组合（大鼠→小鼠）中诱导体液和细胞耐受性。这些动物中嵌合体的诱导与识别大鼠骨髓细胞的IgM天然抗体水平的显著降低有关。类似的方法也可能在猪→人类物种组合中诱导体液和细胞耐受性，从而允许移植来自猪供体的血管化器官。为了确定骨髓移植诱导“天然抗体耐受性”状态的潜力，关键是要确定在猪内皮细胞上表达的所有人类NAb靶抗原是否也在猪骨髓来源的细胞上表达。我们通过评估各种猪骨髓来源的细胞吸收与猪内皮细胞结合的人类IgM和IgG NAb的能力来解决这个问题。我们的结果表明，通过流式细胞术和ELISA检测，猪骨髓细胞及其后代几乎可以吸收所有与猪内皮细胞结合的IgM NAb。吸收的特异性得到了证明，因为在猪骨髓细胞上吸收后，总血清IgM水平仅略有下降，下降程度与用人细胞吸收后观察到的程度相当，而用人细胞吸收不会耗尽与猪内皮细胞结合的NAb。人类IgG与猪内皮细胞的结合也被猪骨髓细胞完全吸收。这些结果表明，成功的猪骨髓移植到人体中可能会诱导“NAb耐受性”状态。此外，猪外周血淋巴细胞、血小板和内皮细胞能够吸收大多数与猪骨髓细胞结合的IgM NAb，这表明使用来自这些组织中任何一种组织抗原的吸收可能会促进该物种组合中的骨髓移植，从而诱导耐受性。
