IMMUNOGLOBULIN HCDR3 IN AUTOIMMUNE DISEASE

免疫球蛋白重链的第三个互补决定区- hcdr3 -位于抗原结合位点的中心，通常决定抗体特异性。构成HCDR3核心的DH基因片段可以翻译成6个阅读框，每个阅读框都具有典型的亲水性特征——带电、疏水或亲水。然而，在几乎所有的物种中，最终的HCDR3序列都丰富于中性的亲水性序列。带电或疏水性HCDR3间隔仅在特殊情况下（如致病性抗dna抗体）才常见。我们的假设认为，带电或疏水的HCDR3结构域被“禁止”，因为它们更有可能产生自我反应性抗体，从而帮助“触发”易感生物的自身免疫性疾病。通过基因靶向，我们正在培养小鼠，其中抗体库已被全局改变，以产生由带电或疏水DH阅读框编码的HCDR3间隔。这些改变的基因库包含天然带电或疏水的HCDR3序列，尽管在典型抗体中很少见，但在一些易自身免疫的小鼠品系中更为常见。初步研究表明，表达带电荷HCDR3间隔的抗体的B细胞可以大量产生，但在外周被选中。我们认为这种外周B细胞的损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能使表达HCDR3亲水性改变的抗体的B细胞存活。带电荷或疏水性HCDR3间隔的抗体被认为更有可能“触发”自身免疫性疾病。为了验证这一假设，我们将突变的DH基因座引入携带自身免疫性疾病易感基因座的小鼠中，例如携带NZM衍生的sle1、sle2和sle3基因座的C57BL/6。这些易感位点在促进具有带电或疏水HCDR3间隔的B细胞发育中的作用将被确定。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，小鼠将接受t非依赖性和t依赖性抗原以及链球菌的攻击。肺炎和流感病毒。最后，将探讨携带带电或疏水性HCDR3间隔的抗体的常见和早期表达在自身免疫性疾病发展中的作用。这些研究应该要么证实要么奠定了在抗体库中使用替代DH阅读框促进自身抗体产生的理论。如果如我们所料，答案是肯定的；因此，所提出的实验具有进一步的潜力，可以帮助我们了解sle1， sle2和sle3在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.