Devlopment of MACIF as a new medicine for regulation of membrane attack complex of complement

两年前，当这项研究开始时，我们只有一系列有限的关于MACIF的证据。我们最初知道MACIF是一种糖基化磷脂酰肌醇（GP 1）锚定蛋白，它特异性地抑制同源补体的膜攻击复合物的形成。(1)用现有的技术几乎不可能制备大量的膜形式的MACIF。(2)我们尝试用三种不同的调味料制备可溶性的MACIF，而不是膜状的MACIF。第一种来自人尿，其含有约0.5 mg/L的可溶性形式。第二种和第三种分别来自大肠杆菌和CHO细胞，其中通过基因工程产生重组可溶性形式的MACIF。(3)MACIF由77个氨基酸、N-糖苷寡糖单元和GP 1寡糖单元组成。尿型有两个单位，而来自E.大肠杆菌中不含N-糖苷寡糖单元，而CHO细胞中只有一个N-糖苷寡糖单元。(4)用豚鼠红细胞溶血抑制法和人补体法测定其活性，三种可溶形式的活性仅为膜形式的0.1%。这一结果表明，膜结合的MACIF的活性是重要的，和碳水化合物部分的活性不是必需的。(5)尿MACIF对绒猴肾低血后再循环引起的细胞毒性有明显的保护作用，但其作用机制尚不清楚。

We had only a limited line of evidence on MACIF when this research had started two years ago. The properties of MACIF we knew at the beginning were that MACIF was a glycosylphosphatidylinositol(GPl)-anchored protein which specifically inhibited the formation of membrane attack complex of homologous complement.New findings obtained from this reseach project are as follows. (1) it was almost impossible to prepare a large amount of the membrane form of MACIFby using presently available techniques. (2) we tried to prepare the soluble forms of MACIF, instead of the membrane form by three dimerent sauces. The first one was from human urine which contained about 0.5 mg/L of the soluble form. The second and third ones were from Eschericia coli and CHO cells, respectively, in which recombinant soluble forms of MACIF were produced by gene engineering. (3) MACIF consists of 77 amino acids, a N-glycosidic oligosaccharide unit and a GPl-oligosaccharide unit. The urine form had both units, and the recombinant form from E. coli had no units while that from CHO cells had only a N-glycosidic oligosaccharide unit. (4) activities of the three soluble forms were only 0.1% as much as that of the membrane form wheer those activities were assayed by the inhibition of hemolysis using guinea pig erythrocytes and human complement. This result indicated that the membrane binding of MACIF was important for the activity, and the carbohydrate moieties were not essential for the activity. (5) the urine MACIF significantly protected the cytotoxicity caused by recirculation after kidney hypaemia of marmosets, although the reaction mechanism was not clear.