Bühler L, Awwad M, Basker M, Gojo S, Watts A, Treter S, Nash K, Oravec G, Chang Q, Thall A, Down J D, Sykes M, Andrews D, Sackstein R, White-Scharf M E, Sachs D H, Cooper D K
Transplantation Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Boston 02129, USA.
Transplantation. 2000 Jun 15;69(11):2296-304. doi: 10.1097/00007890-200006150-00013.
In pig-to-primate organ transplantation, hyperacute rejection can be prevented, but the organ is rejected within days by acute vascular rejection, in which induced high-affinity anti-Gal alpha1-3Gal (alphaGal) IgG and possibly antibodies directed against new porcine (non-alphaGal) antigenic determinants are considered to play a major role. We have explored the role of an anti-CD40L monoclonal antibody in modifying the humoral response to porcine hematopoietic cells in baboons pretreated with a nonmyeloablative regimen.
Porcine peripheral blood mobilized progenitor cells obtained by leukapheresis from both major histocompatibility complex-inbred miniature swine (n=7) and human decay-accelerating factor pigs (n=3) were transplanted into baboons. Group 1 baboons (n=3) underwent whole body (300 cGy) and thymic (700 cGy) irradiation, T cell depletion with ATG, complement depletion with cobra venom factor, short courses of cyclosporine, mycophenolate mofetil, porcine hematopoietic growth factors, and anti-alphaGal antibody depletion by immunoadsorption before transplantation of high doses (2-4 x 10(10)/cells/kg) of peripheral blood mobilized progenitor cells. In group 2 (n=5), cyclosporine was replaced by eight doses of anti-CD40L monoclonal antibodies over 14 days. The group 3 baboons (n=2) received the group 1 regimen plus 2 doses of anti-CD40L monoclonal antibodies (on days 0 and 2).
In group 1, sensitization to alphaGal (with increases in IgM and IgG of 3- to 6-fold and 100-fold, respectively) and the development of antibodies to new non-alphaGal porcine antigens occurred within 20 days. In group 2, no sensitization to alphaGal or non-alphaGal determinants was seen, but alphaGal-reactive antibodies did return to their pre- peripheral blood mobilized progenitor cells transplant levels. In group 3, attenuated sensitization to alphaGal antigens was seen after cessation of cyclosporine and mycophenolate mofetil therapy at 30 days (IgM 4-fold, IgG 8-30-fold), but no antibodies developed against new porcine determinants. In no baboon did anti-CD40L monoclonal antibodies prevent sensitization to its own murine antigens.
We believe these studies are the first to consistently demonstrate prevention of a secondary humoral response after cell or organ transplantation in a pig-to-primate model. The development of sensitization to the murine elements of the anti-CD40L monoclonal antibodies suggests that nonresponsiveness to cell membrane-bound antigen (e.g., alphaGal) is a specific phenomenon and not a general manifestation of immunological unresponsiveness. T cell costimulatory blockade may facilitate induction of mixed hematopoietic chimerism and, consequently, of tolerance to pig organs and tissues.
在猪到灵长类动物的器官移植中，超急性排斥反应可以被预防，但器官会在数天内被急性血管排斥反应所排斥，其中诱导产生的高亲和力抗Galα1-3Gal（αGal）IgG以及可能针对新的猪（非αGal）抗原决定簇的抗体被认为起主要作用。我们探讨了抗CD40L单克隆抗体在改变经非清髓性方案预处理的狒狒对猪造血细胞的体液反应中的作用。
通过白细胞分离术从主要组织相容性复合体近交系小型猪（n = 7）和人衰变加速因子猪（n = 3）获得的猪外周血动员祖细胞被移植到狒狒体内。第1组狒狒（n = 3）在移植高剂量（2 - 4×10¹⁰/细胞/kg）外周血动员祖细胞之前，接受全身（300 cGy）和胸腺（700 cGy）照射、用抗胸腺细胞球蛋白进行T细胞清除、用眼镜蛇毒因子进行补体清除、短期使用环孢素、霉酚酸酯、猪造血生长因子以及通过免疫吸附清除抗αGal抗体。在第2组（n = 5）中，在14天内用八剂抗CD40L单克隆抗体替代环孢素。第3组狒狒（n = 2）接受第1组方案加两剂抗CD40L单克隆抗体（在第0天和第2天）。
在第1组中，对αGal的致敏（IgM和IgG分别增加3至6倍和100倍）以及针对新的非αGal猪抗原的抗体在20天内出现。在第2组中，未观察到对αGal或非αGal决定簇的致敏，但αGal反应性抗体确实恢复到外周血动员祖细胞移植前的水平。在第3组中，在30天停用环孢素和霉酚酸酯治疗后，对αGal抗原的致敏减弱（IgM 4倍，IgG 8至30倍），但未产生针对新的猪决定簇的抗体。在任何狒狒中，抗CD40L单克隆抗体均未预防对其自身鼠抗原的致敏。
我们认为这些研究首次在猪到灵长类动物模型中一致地证明了在细胞或器官移植后预防二次体液反应。对抗CD40L单克隆抗体的鼠源性成分产生致敏表明，对细胞膜结合抗原（如αGal）无反应是一种特定现象，而非免疫无反应的普遍表现。T细胞共刺激阻断可能有助于诱导混合造血嵌合体，从而诱导对猪器官和组织的耐受性。
