异种超急性排斥补体旁路作用机制的探讨

An explaration to the mechanism of alternative complement pathway activation in xenograft hyperacute rejection

为探讨异种（猪／人）超急性排斥时补体旁路途径的作用机制。选择猪血管内皮细胞为靶，人血清为天然抗体和补体源，用四唑盐法（MTT）行补体依赖的细胞毒反应（CDC），建立体外超急性排斥模型。结果：人血清能溶解58±5％的猪血管内皮细胞。Clq缺乏的人血清（阻断经典途径）仅溶解37±7％猪细胞（P＜0．01）。B因子缺乏的人血清（阻断旁路途径）仅溶解42±10％的猪细胞（P＜0．01）。同种猪血清及加热灭活补位的人血清不溶猪细胞。将经典途径及旁路途径缺陷的人血清等体积混合，其细胞毒作用恢复正常。同样，Clq缺乏人血清和B因子缺乏人血清分别加入Clq和B因子后，血清细胞毒作用亦恢复正常。结论：在这一体外异种超急性排斥模型中，补体经典和旁路两条途径均参与超急性排斥反应。本文结果提示抑制猪／人之间的超急性排斥应考虑补体旁路途径激活的问题。

To study the role of alternative complement pathway activation in porcine to human xenograft hyperacute rejection. A model of hyperacute xenograft rejection was established with CDC test (MTT method)using porcine endothelial cells in culture as target and human sera as the source of natural antibodies and complement. Pure human serum lysed 58±5% of pig endothelial cells. Selective inhibition of the direct pathway by using Clq-deficient human serum only killed 37±7% of pig endothelial cells (P<0. 01 versus normal serum). When alternative pathway was selectively inhibited by using factor B-deficient human serum, only 42±10% of pig endothelial cells were lysed (P<0. 01 versus normal serum). Syngenic normal pig serum and heat-inactivated serum were not cytotoxic. Mixing serum with deficient direct pathway and serum with deficient alternative pathway restored the cytotoxicity to normal levels. Similarly, the cytotoxic activity of deficient serum supplemented with purified Clq and factor B at physiological concentration reached that of normal human serum. In this in vitro hyperacute rejection, both pathways of complement activation were involved,suggesting that regimens designed to inhibit hyperacute rejection of swine graft into human should take into account the activation of alternative complement pathway.