MOLECULAR GENETICS OF COMPLEMENT C4

人类人类白细胞抗原复合体的一个特征是多态(I)。就像I班和 补体基因座的第三类第四组分，即C4a和C4a C4b等位基因高度多态，有35个以上的等位基因。遗传学研究 已经绘制了对许多疾病的易感性，特别是免疫 复杂(Ic)疾病，与人类白细胞抗原的这一区域有关。长期目标 这一建议的目的是理解基因的功能重要性 多态以及它可能如何与免疫反应和 疾病易感性。这一目标被组织成三个 具体目标：(一)确定结构基础和功能 C4基因多态的意义；(2)确定遗传效应 C4亚型对人体免疫反应的影响；(3)发展 分析C4蛋白在免疫中作用的遗传模型 体内反应。 第一个目标是检验这样一种假设，即同型基因和 异型残基影响与IC的共价结合。人类补体C4a和C4b 编码序列将使用定点突变技术进行突变。 了解这些残基对结合的影响很重要，因为 结合的效率直接决定了激活的程度 这条小路。 这一提议的第二个目的是检验以下假设： 对乙肝疫苗的应答是由于纯合子C4a零等位基因所致。 这将通过将先前的研究扩大到包括个人来进行测试 C4a零等位基因纯合，但在其他人类白细胞抗原单倍型 而不是B8 DR3。C4亚型影响免疫应答的研究 某些疫苗将具有重要意义。 第三个目标是培育一种C4缺陷型小鼠。这 菌株将在本提案中用于：(1)角色的表征 免疫反应中的补体；(2)遗传操作，如 插入人C4a或C4b转基因；(3)直接比较 C4a和C4b转基因小鼠的免疫应答；以及(4)发育 一种人类替代疗法的策略。 综上所述，(1)生物化学研究的综合方法 C4结构变异的重要性；(2)人类疫苗接种 具有两种不同抗原的C4a或C4b缺失等位基因均为纯合子； (3)构建C4缺陷型和C4a/C4b转基因小鼠 补体C4在免疫应答中作用的生物学研究 多态对其作用的影响；将回答以下重要问题 将导致未来针对人类疾病的治疗。

A hallmark of the HLA complex in man is polymorphism (i). Like class I and II loci the class III fourth component of complement loci, i.e. C4A and C4B, are highly polymorphic with more than 35 alleles. Genetic studies have mapped susceptibility to a number of diseases, in particular immune complex (ic) disease, to this region of the HLA. The long term objective of this proposal is to understand the functional importance of the genetic polymorphism and how it might be related to the immune response and disease susceptibility. This objective has been organized into three specific aims: (1) Determine the structural basis and functional significance of C4 polymorphism; (2) Determine the affect of genetic variation of the C4 isotypes on the human immune response; (3) Develop genetic models for the analysis of the role of C4 protein in the immune response in vivo. The first aim proposes to test the hypothesis that both the isotypic and allotypic residues affect covalent binding to the ic. Human C4A and C4B coding sequences will be mutated using site-directed mutagenesis. Understanding the affect these residues have on binding is important since the efficiency of binding directly determines the extent of activation of the pathway. The second aim of this proposal is to test the hypothesis that non- response to hepatitis B vaccine is due to homozygous C4A null alleles. This will be tested by extending the previous study to include individuals that are homozygous for the C4A null allele but on HLA haplotypes other than B8 DR3. The finding that C4 isotype affects the immune response to certain vaccines would be of significant importance. The third aim proposes to develop a C4 deficient strain of mouse. This strain will be used in this proposal for: (1) characterization of the role of complement in the immune response; (2) genetic manipulation such as insertion of transgenes of either human C4A or C4B; (3) direct comparison of the immune response by C4A and C4B transgenic mice; and (4) developing a strategy for a replacement therapy in humans. In summary, the combined approach of (1) biochemical studies on the importance of the structural variation of C4; (2) vaccination of humans homozygous for either C4A or C4B null alleles with two different antigens; and (3) construction of C4 deficient and C4A/C4B transgenic mice for biological studies on both the role of C4 in the immune response and the affect of polymorphism on its role; will answer important questions that will lead to future therapy against human disease.