Finn J E, Li P K, Lai K N, Mathieson P W
Department of Medicine, University of Cambridge, UK.
Am J Kidney Dis. 1994 Apr;23(4):543-6. doi: 10.1016/s0272-6386(12)80376-3.
The third component of complement (C3) exists in two main allotypic forms, C3S and C3F. An increased frequency of the rarer C3F allele has been reported in several autoimmune conditions, including immunoglobulin A nephropathy (IgAN), in white patients. C3F is known to be rare in the Chinese population, but C3 allotypes have not been studied in Chinese patients with IgAN. The molecular basis of the S/F polymorphism has been established recently: a single base change at the DNA level encodes a single amino acid substitution in the protein. A second polymorphism, closely linked to the first, is defined by the monoclonal antibody HAV 4-1, and also is due to a single base change. These polymorphisms therefore can be analyzed at the DNA level. We have used the amplification refractory mutation system, a modification of the polymerase chain reaction, to analyze these two C3 polymorphisms on genomic DNA from 133 Hong Kong Chinese individuals: 54 patients with IgAN and 79 controls. No C3F alleles were present in either group: all individuals were homozygous C3S. Twenty-six patients were also allotyped for the HAV 4-1 polymorphism; all 26 were homozygous HAV 4-1 negative, as would be predicted from the close linkage of this allotype to C3S in other populations. These data indicate that C3F is not a susceptibility allele for IgAN in Hong Kong Chinese individuals, and confirm in a large DNA-based study the rarity of C3F in this population.
补体的第三成分（C3）存在两种主要的同种异型形式，即C3S和C3F。在包括白人患者的免疫球蛋白A肾病（IgAN）在内的几种自身免疫性疾病中，已报道较罕见的C3F等位基因频率增加。已知C3F在中国人群中很罕见，但尚未对中国IgAN患者的C3同种异型进行研究。S/F多态性的分子基础最近已确定：DNA水平上的单个碱基变化编码蛋白质中的单个氨基酸取代。与第一个紧密连锁的第二个多态性由单克隆抗体HAV 4-1定义，同样也是由于单个碱基变化。因此，这些多态性可以在DNA水平上进行分析。我们使用了聚合酶链反应的一种改进方法——扩增阻滞突变系统，来分析133名香港华人个体基因组DNA上的这两种C3多态性：54例IgAN患者和79名对照。两组中均不存在C3F等位基因：所有个体均为纯合C3S。26例患者也进行了HAV 4-1多态性的同种异型分型；所有26例均为纯合HAV 4-1阴性，正如从其他人群中该同种异型与C3S的紧密连锁所预测的那样。这些数据表明，C3F不是香港华人个体中IgAN的易感等位基因，并在一项基于大量DNA的研究中证实了该人群中C3F的罕见性。
