Clearance of mobilized porcine peripheral blood progenitor cells is delayed by depletion of the pragocytic reticuloendothelial system in baboons
Clearance of mobilized porcine peripheral blood progenitor cells is delayed by depletion of the pragocytic reticuloendothelial system in baboons
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DOI：
10.1097/00007890-200110150-00017
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发表时间：
2001-10-15
期刊：
影响因子：
6.2
通讯作者：
Cooper, DKC
中科院分区：
文献类型：
--
作者：
Basker, M;Alwayn, IPJ;Cooper, DKC
导论.通过建立混合造血嵌合体在非人灵长类动物中实现对猪组织的免疫耐受的尝试受到来自循环的含有祖细胞（pPBPC）的动员的猪白细胞的快速清除的阻碍。将1- 2x 10（10）pPBPC/kg输注到循环抗α Gal和补体已耗尽的狒狒中后18小时，这些细胞几乎无法通过流式细胞术检测到。本研究的目的是确定机制，有助于快速清除狒狒的pPBPC。这是通过消耗，或阻断Fc受体的，吞噬网状内皮系统（RES）的细胞使用甲膦酸脂质体（ML）或静脉注射免疫球蛋白（Mg），分别。在剂量探索和毒性研究中使用狒狒（初步研究，n=4），以评估ML对体内巨噬细胞消耗的影响。在另一项研究中，狒狒（n=9）接受了旨在诱导免疫耐受的非清髓性预处理方案（NMCR），包括脾切除术、全身照射（300 cGy）或环磷酰胺（80 mg/kg）、胸腺照射（700 cGy）、T细胞耗竭、用眼镜蛇毒因子耗竭补体、霉酚酸酯、抗CD 154单克隆抗体、和抗-aGal抗体的多次体外免疫吸附。将狒狒分为3组：1组（n=5）NMCR+pPBPC移植; 2组（n=2）NMCR+ML+pPBPC移植; 3组（n=2）NMCR+IVIg+pPBPC移植。采用荧光激活细胞分选仪和聚合酶链反应（PCR）检测血液中的猪细胞。初步研究：ML以剂量依赖性方式有效地消耗循环中的巨噬细胞。第1组：输注1 × 10（10）pPBPC/kg后2小时，平均检测到14%的猪细胞。18小时后，可检测到的猪细胞通常少于1.5%。第二组：输注后2小时检测到显著较高水平的猪细胞嵌合体（55-78%），即使输注的pPBPC数量较少（0.5-1 x 10（10）/ kg），并且这些水平在IS小时后更好地维持（10-52%）。第3组：在1只狒狒中，输注1 × 10（10）pPBPC/kg后2小时检测到4.4%的猪细胞。然而，18小时后，检测到7.4%的猪细胞。第二只狒狒在输注4 x 10（10）pPBPC/kg后2小时死亡，总白色血细胞计数为90，000，其中70%为猪细胞。通过PCR测定，未检测到组间微嵌合体的差异。这是第一项在大型动物模型中报告通过用ML耗竭巨噬细胞有效降低吞噬功能的研究。用ML耗尽巨噬细胞导致最初较高的嵌合状态，并延长狒狒循环猪细胞的存活时间。用IVIg阻断巨噬细胞功能的效果更温和。因此，RES的细胞在从狒狒的循环中清除pPBPC中起主要作用。RES的耗尽或阻断可能有助于实现混合造血嵌合体和诱导对不一致异种移植物的耐受。
Introduction. Attempts to achieve immunological tolerance to porcine tissues in nonhuman primates through establishment of mixed hematopoietic chimerism are hindered by the rapid clearance of mobilized porcine leukocytes, containing progenitor cells (pPBPCs), from the circulation. Eighteen hours after infusing 1-2x10(10) pPBPC/kg into baboons that had been depleted of circulating anti-alpha Gal and complement, these cells are almost undetectable by flow cytometry. The aim of the present study was to identify mechanisms that contribute to rapid clearance of pPBPCs in the baboon. This was achieved by depleting, or blocking the Fc-receptors of, cells of the phagocytic reticuloendothelial system (RES) using medronate liposomes (MLs) or intravenous immunoglobulin (Mg), respectively.Methods. Baboons (preliminary studies, n=4) were used in a dose-finding and toxicity study to assess the effect of MLs on macrophage depletion in vivo. In another study, baboons (n=9) received a nonmyeloablative conditioning regimen (NMCR) aimed at inducing immunological tolerance, including splenectomy, whole body irradiation (300 cGy) or cyclophosphamide (80 mg/kg), thymic irradiation (700 cGy), T-cell depletion, complement depletion with cobra venom factor, mycophenolate mofetil, anti-CD154 monoclonal antibody, and multiple extracorporeal immunoadsorptions of anti-aGal antibodies. The baboons were divided into three groups: Group 1 (n=5) NMCR+pPBPC transplantation; Group 2 (n=2) NMCR+ML+pPBPC tranplantation; and Group 3 (n=2) NMCR+IVIg+pPBPC transplantation. Detection of pig cells in the blood was assessed by fluorescence-activated cell sorter and polymerase chain reaction (PCR).Results. Preliminary studies: ML effectively depleted macrophages from the circulation in a dose-dependent manner. Group 1: On average, 14% pig cells were detected 2 hr postinfusion of 1x10(10) pPBPC/kg. After 18 hr, there were generally less than 1.5% pig cells detectable. Group 2: Substantially higher levels of pig cell chimerism (55-78%) were detected 2 hr postinfusion, even when a smaller number (0.5-1 x 10(10)/ kg) of pPBPCs had been infused, and these levels were better sustained IS hr later (10-52%). Group 3: In one baboon, 4.4% pig cells were detected 2 hr after infusion of 1x10(10) pPBPC/kg. After 18 hr, however, 7.4% pig cells were detected. A second baboon died 2 hr after infusion of 4 x 10(10) pPBPC/kg, with a total white blood cell count of 90,000, of which 70% were pig cells. No differences in microchimerism could be detected between the groups as determined by PCR.Conclusions. This is the first study to report an efficient decrease of phagocytic function by depletion of macrophages with MLs in a large-animal model. Depletion of macrophages with MLs led to initial higher chimerism and prolonged the survival of circulating pig cells in baboons. Blockade of macrophage function with IVIg had a more modest effect. Cells of the RES, therefore, play a major role in clearing pPBPCs from the circulation in baboons. Depletion or blockade of the RES may contribute to achieving mixed hematopoietic chimerism and induction of tolerance to a discordant xenograft.