IMMUNOGLOBULIN HCDR3 IN AUTOIMMUNE DISEASE

免疫球蛋白重链的第三互补决定区-HCDR 3-位于抗原结合位点的中心，通常决定抗体特异性。 构成HCDR 3核心的DH基因片段在六个阅读框架中是潜在可翻译的，每个框架具有特征性的亲水性特征-带电荷的、疏水的或亲水的。 然而，在几乎所有物种中，最终的HCDR 3库富含中性亲水序列。带电或疏水HCDR 3间隔仅在特殊情况下常见（例如病原性抗DNA抗体）。我们的假设认为，带电或疏水的HCDR 3结构域是“禁止的”，因为它们更可能产生自身反应性抗体，从而有助于在易感生物体中“触发”自身免疫性疾病。 通过基因靶向，我们正在产生小鼠，其中抗体库已被全面改变，以产生由带电或疏水DH阅读框编码的HCDR 3间隔。 这些改变的库含有天然带电或疏水的HCDR 3序列，尽管在典型抗体中罕见，但在一些自身免疫易感小鼠品系中更常见。 初步研究表明，表达具有带电HCDR 3间隔的抗体的B细胞可以大量产生，但在外周中被选择。 我们认为这种外周B细胞的丢失是由于自身反应性。 携带降低自身抗体形成屏障的基因的小鼠可以使表达具有改变的HCDR 3亲水性的抗体的B细胞存活。 具有带电或疏水HCDR 3间隔的抗体被认为更可能“触发”自身免疫性疾病。为了检验这一假设，我们将突变DH基因座引入到携带确定的自身免疫性疾病易感基因座的小鼠中，例如携带NZM衍生的sle 1、sle 2和sle 3基因座的C57 BL/6。 将确定这些易感性基因座在促进具有带电或疏水HCDR 3间隔的B细胞发育中的作用。 为了确定库的改变是否会影响小鼠对正常刺激的反应能力，将用T非依赖性和T依赖性抗原以及链球菌攻击小鼠。肺炎和流感病毒。 最后，将检查携带带电或疏水HCDR 3间隔的抗体的常见和早期表达对自身免疫性疾病发展的作用。 这些研究应该证实或搁置在抗体库中使用替代DH阅读框架促进自身抗体产生的理论。 如果正如我们所预期的那样，答案是肯定的，那么所提出的实验有进一步的潜力帮助我们理解sle 1，sle 2和sle 3在消除异常抗体库的正常调节中可能发挥的作用。

The third complementarity determining region of the immunoglobulin heavy chain-HCDR3-lies at the center of the antigen-binding site and typically determines antibody specificity. The DH gene segments that compose the core of HCDR3 are potentially translatable in six reading frames, each with a characteristic hydropathicity signature-charged, hydrophobic, or hydrophilic. However, in virtually all species the final HCDR3 repertoire is enriched for neutral, hydrophilic sequence. Charged or hydrophobic HCDR3 intervals are common only in exceptional circumstances (e.g. pathogenic anti-DNA antibodies). Our hypothesis holds that charged or hydrophobic HCDR3 domains are "forbidden" because they are more likely to generate self- reactive antibodies and thus help "trigger" autoimmune disease in susceptible organisms. Through gene targeting, we are generating mice wherein the antibody repertoire has been globally altered to produce HCDR3 intervals encoded by either charged or hydrophobic DH reading frames. These altered repertoires contain native charged or hydrophobic HCDR3 sequence that, although rare in typical antibodies, is more common in some autoimmune prone strains of mice. Preliminary studies indicate that B cells expressing antibodies with charged HCDR3 intervals can be generated in high numbers, but are selected against in the periphery. We propose that this peripheral loss of B cells is due to self-reactivity. Mice that bear genes that reduce the barrier to the formation of autoantibodies may enable B cells expressing antibodies with altered HCDR3 hydropathicity to survive. Antibodies with charged or hydrophobic HCDR3 intervals are proposed to be more likely to "trigger" autoimmune disease. In order to test this hypothesis, we will introduce mutant DH loci into mice bearing defined susceptibility loci for autoimmune disease, e.g. C57BL/6 bearing the NZM derived sle1, sle2, and sle3 loci. The role of these susceptibility loci in facilitating the development of B cells with charged or hydrophobic HCDR3 intervals will be determined. To determine whether alteration of the repertoire can affect the ability of the mice to respond to normal stimuli, the mice will be challenged with T-independent and T-dependent antigens, and with Strep. pneumoniae and influenza virus. Finally, the role of common and early expression of antibodies bearing charged or hydrophobic HCDR3 intervals on the development of autoimmune disease will be examined. These studies should either confirm or lay to rest the theory that use of alternative DH reading frames in the antibody repertoire promotes the production of autoantibodies. If, as we expect, the answer is yes; then the proposed experiments have the further potential of helping us understand the role that sle1, sle2, and sle3 may have in voiding normal regulation of abnormal antibody repertoires.