Kroshus T J, Bolman R M, Dalmasso A P
Department of Surgery, University of Minnesota, Minneapolis, USA.
Transplantation. 1996 Jul 15;62(1):5-12. doi: 10.1097/00007890-199607150-00002.
In the pig-to-primate model, xenograft hyperacute rejection (HAR) is mediated by antibody and complement. Previous studies have implicated xenoreactive IgM natural antibody (nAb) as the predominant immunoglobulin involved in HAR. To further evaluate the role of IgM, we selectively reduced IgM levels in human blood, without changing IgG and IgA levels, and then used this blood to perfuse porcine hearts ex vivo. Specific IgM depletion was accomplished with an immunoabsorption column containing sheep anti-human IgM (mu-chain specific) conjugated to Sepharose beads. Human blood was separated into plasma and cellular components. For control experiments, those components were unmodified and recombined in the perfusion system. For experiments with IgM reduced blood, the plasma was passed through the IgM column. Immunoabsorption resulted in approximately 90% reduction in xenoreactive IgM levels, as measured by ELISA. Porcine hearts perfused with unmodified human blood survived 25 +/- 5.6 min (n=5). Porcine hearts perfused with human blood containing reduced levels of IgM survived 229 +/- 45.2 min (n=4; P<0.01). Organ survival was negatively associated with xenoreactive IgM nAb levels measured immediately before perfusion (r=-0.83; P=0.01), and not with IgG nAb levels (r=-0.21; P=0.62). The ability of plasma from IgM-depleted blood to elicit complement activation, measured by iC3b binding to porcine aortic endothelial cells in vitro, was also strongly associated with IgM xenoreactive nAb levels (r=0.92; P<0.0001). Control hearts perfused with unmodified human blood showed typical widespread histologic features of HAR, while porcine hearts perfused with IgM-reduced blood demonstrated milder and less uniform changes. Immunopathological analysis of heart tissues obtained at the completion of each study showed similar deposition of IgG between groups but markedly less IgM, C3, C4, and C9 in the IgM reduction group. These results suggest that selective IgM reduction delays HAR with prolongation of survival and that xenoreactive IgM may be the predominant immunoglobulin involved in HAR in the pig-to-human combination.
在猪到灵长类动物模型中，异种移植超急性排斥反应（HAR）由抗体和补体介导。先前的研究表明，异种反应性IgM天然抗体（nAb）是参与HAR的主要免疫球蛋白。为了进一步评估IgM的作用，我们选择性降低了人血液中的IgM水平，同时不改变IgG和IgA水平，然后用这种血液对猪心脏进行离体灌注。通过含有与琼脂糖珠偶联的羊抗人IgM（μ链特异性）的免疫吸附柱实现特异性IgM清除。将人血液分离成血浆和细胞成分。在对照实验中，这些成分未作处理并在灌注系统中重新组合。对于用降低了IgM的血液进行的实验，血浆通过IgM柱。通过ELISA检测，免疫吸附使异种反应性IgM水平降低了约90%。用未处理的人血液灌注的猪心脏存活了25±5.6分钟（n = 5）。用IgM水平降低的人血液灌注的猪心脏存活了229±45.2分钟（n = 4；P<0.01）。器官存活与灌注前立即测定的异种反应性IgM nAb水平呈负相关（r = -0.83；P = 0.01），与IgG nAb水平无关（r = -0.21；P = 0.62）。通过体外测定iC3b与猪主动脉内皮细胞的结合来衡量，降低了IgM的血液中的血浆引发补体激活的能力也与IgM异种反应性nAb水平密切相关（r = 0.92；P<0.0001）。用未处理的人血液灌注的对照心脏表现出典型的广泛的HAR组织学特征，而用降低了IgM的血液灌注的猪心脏表现出较轻微且不太一致的变化。在每项研究结束时获得的心脏组织的免疫病理学分析表明，各组之间IgG的沉积相似，但在降低IgM组中IgM、C3、C4和C9明显较少。这些结果表明，选择性降低IgM可延迟HAR并延长存活时间，并且异种反应性IgM可能是猪到人组合中参与HAR的主要免疫球蛋白。
