CHROMOSOME 6P AND DEVELOPMENTAL DEFECTS

系统性红斑狼疮（SLE）是一种自身免疫性疾病，在美国影响超过20万女性，其特点是抗核抗体和肾小球肾炎的高发。SLE的一个主要危险因素是早期经典途径补体成分C1、C2或C4缺乏。这种关联呈现出一种悖论，因为人们并不认为免疫缺陷会导致自身免疫性疾病。一种解释是，早期补体参与维持B细胞的耐受性，在缺乏补体的情况下，自反应性B细胞会在外围积聚，在那里它们可能被激活。本提案的目的是验证这一假设，具体分为3个目的：(i)验证早期经典途径补体成分C1、C4和C3直接参与自身反应性B淋巴细胞负选择的假设。在此目的中使用的方法是用两种成熟的免疫球蛋白转基因模型（抗hel和抗dsdna）培养缺乏C1、C4或C3的小鼠，并确定补体是否对B细胞能量至关重要。（ii）第二个目标将在定义明确的狼疮小鼠模型（即lpr菌株）中检验经典途径补体缺乏导致疾病严重程度增加的假设。该目的的优势在于，它将检验早期补体在对天然狼疮抗原（如dsDNA和核蛋白）的自身免疫反应中的重要性。（iii）第三个目标将验证C4null小鼠受损的自我耐受性可以通过蛋白质替代或基因治疗来拯救的假设，如果是这样，将C4A和C4B同型进行比较。本研究还将研究C4在B细胞耐受中的机制，使用与sHEL抗原连接的C4d融合蛋白，通过C4d解除免疫复合物的偶联增溶作用，使抗原靶向到淋巴细胞室。这一目标很重要，因为它将建立狼疮蛋白或基因治疗的可行性，并澄清我们对B细胞耐受性的理解。

Systemic lupus erythematosus (SLE) is an autoimmune disorder which affects over 200,000 women in the USA and it is characterized by anti-nuclear antibodies and a high incidence of glomerulonephritis. A major risk factor for SLE is deficiency in early classical pathway complement components C1, C2 or C4. This association presents a paradox because it is not expected that an immune deficiency would result in an autoimmune disease. One explanation is that early complement is involved in maintenance of B cell tolerance and in its absence, self-reactive B cells accumulate in the periphery where they potentially may be activated. The goal of this proposal is to test this hypothesis and it is divided into 3 specific aims: (i) Test the hypothesis that early classical pathway complement components C1, C4 and C3 are directly involved in negative selection of self-reactive B lymphocytes. The approach used in this aim is to breed mice deficient in C1, C4, or C3 with two well established immunoglobulin transgenic models (anti-HEL and anti-dsDNA) and determine if complement is essential in B cell anergy. (ii) The second aim will test the hypothesis that deficiency in classical pathway complement results in increased severity of disease in a well defined mouse model of lupus, i.e. lpr strain. The advantage of this aim is that it will examine the importance of early complement in the autoimmune response to natural lupus antigens such as dsDNA and nuclear proteins. (iii) The third aim will test the hypothesis that impaired self-tolerance in C4null mice can be rescued by protein replacement or gene therapy and if so compare C4A and C4B isotypes. It will also examine the mechanism of C4 in B cell tolerance using a fusion protein of C4d linked to sHEL antigen to uncouple solubilization of immune complexes from targeting of antigen to the lymphoid compartment via C4d. This aim is important as it will establish the feasibility of protein or gene therapy in lupus and clarify our understanding of B cell tolerance.