Kinoshita T, Medof M E, Silber R, Nussenzweig V
J Exp Med. 1985 Jul 1;162(1):75-92. doi: 10.1084/jem.162.1.75.
Decay-accelerating factor (DAF) is a 70,000 Mr protein that has been isolated from the membrane of red cells. The function of DAF is to inhibit the assembly of amplifying enzymes of the complement cascade on the cell surface, thereby protecting them from damage by autologous complement. We raised monoclonal antibodies to DAF and used them to study its distribution in cells from the peripheral blood of normal individuals and of patients with paroxysmal nocturnal hemoglobinuria (PNH), a disease characterized by the unusual susceptibility of red cells to the hemolytic activity of complement. The results of immunoradiometric assays and of fluorescence-activated cell sorter analysis showed that DAF was present not only on red cells but was widely distributed on the surface membrane of platelets, neutrophils, monocytes, and B and T lymphocytes. By Western blotting, we observed small but consistent differences in the Mr of DAF from the membranes of various cell types. Quantitative studies showed that phagocytes and B lymphocytes, which presumably enter more frequently in contact with immune complexes and other potential activators of complement, had the highest DAF levels. As previously reported by others, the red cells from PNH patients were DAF deficient. When the patients' red cells were incubated in acidified serum (Ham test), only the DAF-deficient cells were lysed. In addition, we detected defects in DAF expression on platelets and all types of leukocytes. The observed patterns of DAF deficiency in these patients were consistent with the concept that the PNH cells were of monoclonal origin. In one patient, abnormal and normal cells were found only in the erythroid, myeloid, and megakaryocytic lineages. In two other patients, the lymphocytes were also DAF deficient, suggesting that a mutation occurred in a totipotent stem cell. It appears, therefore, that the lesion leading to PNH can occur at various stages in the differentiation of hematopoietic cells.
衰变加速因子（DAF）是一种分子量为70,000的蛋白质，已从红细胞膜中分离出来。DAF的功能是抑制补体级联反应的放大酶在细胞表面的组装，从而保护细胞免受自身补体的损伤。我们制备了针对DAF的单克隆抗体，并利用它们研究其在正常个体和阵发性夜间血红蛋白尿（PNH）患者外周血中的细胞分布。PNH是一种以红细胞对补体溶血活性异常敏感为特征的疾病。免疫放射分析和荧光激活细胞分选分析结果表明，DAF不仅存在于红细胞上，还广泛分布于血小板、中性粒细胞、单核细胞以及B和T淋巴细胞的表面膜上。通过蛋白质印迹法，我们观察到来自不同细胞类型膜的DAF分子量存在微小但一致的差异。定量研究表明，吞噬细胞和B淋巴细胞可能更频繁地接触免疫复合物和补体的其他潜在激活剂，其DAF水平最高。正如其他人先前报道的那样，PNH患者的红细胞缺乏DAF。当将患者的红细胞在酸化血清中孵育（Ham试验）时，只有缺乏DAF的细胞被裂解。此外，我们检测到血小板和所有类型白细胞上DAF表达存在缺陷。在这些患者中观察到的DAF缺陷模式与PNH细胞起源于单克隆的概念一致。在一名患者中，仅在红系、髓系和巨核细胞系中发现了异常细胞和正常细胞。在另外两名患者中，淋巴细胞也缺乏DAF，这表明在全能干细胞中发生了突变。因此，导致PNH的病变可能发生在造血细胞分化的各个阶段。
