Second Affiliated Hospital, University of South China, Hengyang City, Hunan, China; Xenotransplantation Program, Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA.
Xenotransplantation Program, Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA.
Transpl Immunol. 2019 Dec;57:101243. doi: 10.1016/j.trim.2019.101243. Epub 2019 Aug 28.
Measurement of serum anti-pig antibodies is an important parameter in immune monitoring after pig-to-nonhuman primate xenotransplantation. Pig aortic endothelial cells (pAECs) are commonly used for this purpose. However, human (h) CTLA4-Ig (abatacept/belatacept) could bind to pCD80/86 on the cells, and a secondary antibody (i.e., anti-human IgG) may recognize hCTLA4-Ig (in the absence of serum anti-pig IgG antibody binding to pAECs), potentially leading to misinterpretation of the results. Our aim was to determine whether hCTLA4-Ig binding to pAECs is associated with false-positive results.
Sera were obtained from (i) naïve baboons (n = 3) and (ii) baboons (n = 2) that had undergone pig artery patch transplantation with/without hCTLA4Ig therapy. Serum IgM and IgG binding to (i) AECs, (ii) red blood cells (RBCs), and (iii) CD3T cells in peripheral blood mononuclear cells (PBMCs) from an α1,3-galactosyltransferase gene-knockout pig expressing human CD46 (GTKO/hCD46) was measured by flow cytometry in the presence or absence of hCTLA-4Ig. Complement-dependent cytotoxicity (CDC) of wild-type (WT) pAECs by hCTLA4Ig was measured by flow cytometry.
Sera containing hCTLA4-Ig demonstrated significantly increased IgG (but not IgM) binding to pAECs (relative geometric mean [rGM] = 1.8) compared to sera without hCTLA-4Ig (rGM =1.3) (p < .01). In contrast, there was no increased binding to pRBCs or CD3T cells. hCTLA4-Ig did not result in cytotoxicity of WT pAECs.
pAECs might not be an optimal cell to investigate anti-pig IgG binding when hCTLA4-Ig is administered to the recipient, as a false-positive result may result from hCTLA4-Ig binding to the pAECs. CD3T cells would be preferable targets (compared to pRBCs) because they express both carbohydrate and MHC class I/II antigens.
在猪到非人类灵长类动物异种移植后，血清抗猪抗体的测量是免疫监测的一个重要参数。猪主动脉内皮细胞（pAEC）常用于此目的。然而，人 CTLA4-Ig（阿巴西普/贝那西普）可能与细胞上的 pCD80/86 结合，并且第二抗体（即抗人 IgG）可能识别 hCTLA4-Ig（在没有血清抗猪 IgG 抗体与 pAEC 结合的情况下），这可能导致结果的误读。我们的目的是确定 hCTLA4-Ig 与 pAEC 的结合是否与假阳性结果有关。
从（i）未处理的狒狒（n=3）和（ii）接受过猪动脉补片移植的狒狒（n=2）中获得血清，其中有/没有接受 hCTLA4Ig 治疗。通过流式细胞术测量来自表达人 CD46（GTKO/hCD46）的α1,3-半乳糖基转移酶基因敲除猪的外周血单个核细胞（PBMC）中的（i）AEC、（ii）红细胞（RBC）和（iii）CD3T 细胞的血清 IgM 和 IgG 与 hCTLA-4Ig 的结合，有无 hCTLA4Ig 存在。通过流式细胞术测量野生型（WT）pAEC 中 hCTLA4Ig 的补体依赖性细胞毒性（CDC）。
含有 hCTLA4-Ig 的血清与不含 hCTLA-4Ig 的血清相比，pAEC 上 IgG（但不是 IgM）的结合显著增加（相对几何平均值[rGM]分别为 1.8 和 1.3）（p<0.01）。相比之下，与 pRBC 或 CD3T 细胞结合没有增加。hCTLA4-Ig 未导致 WT pAEC 的细胞毒性。
当 hCTLA4-Ig 给予受者时，pAEC 可能不是研究抗猪 IgG 结合的最佳细胞，因为 hCTLA4-Ig 与 pAEC 的结合可能导致假阳性结果。与 pRBC 相比，CD3T 细胞将是更好的靶标（因为它们表达碳水化合物和 MHC Ⅰ/Ⅱ抗原）。
