Molecular biological study＼ies in a novel peripheral nerve myelin protein and its application to clinical neurology

我们试图表征35-kd抗原识别的血清IgG患者恶性淋巴瘤和周围神经病变。在western blotting上，血清IgG在人、牛和小鼠周围神经（PN）中与35-kd抗原反应，但与其他神经和非神经组织不反应。免疫组化分析显示PN致密髓鞘中IgG具有免疫反应性。我们构建了人坐骨神经cDNA文库，并利用患者IgG进行筛选。我们鉴定出三个独立的克隆体。对这些克隆的插入片段进行同源性分析，发现插入片段与p0cdna同源。然而，所有的插入都对应于P0 cDNA的3'-非翻译区。制备人、牛坐骨神经髓磷脂标本，对35-kd抗原进行生化分析。采用sds -聚丙烯酰胺凝胶电泳技术，从粗髓磷脂中纯化35-kd抗原。比较35-kd抗原与蛋白P0对患者IgG和单克隆抗P0抗体的免疫反应性，35-kd抗原与两种抗体均有反应，而P0仅与单克隆抗P0抗体有反应。这些结果表明35-kd抗原可能是P0的同型。然而，这些针对35-kd抗原的自身抗体的存在似乎没有什么病理意义，因为在没有相关周围神经病变的恶性淋巴瘤患者的血清中也发现了针对该抗原的循环自身抗体。

We tried to characterize a 35-kd antigen recognized by the serum IgG of a patient with malignant lymphoma and peripheral neuropathy. On western blotting, the serum IgG reacted with a 35-kd antigen in human, bovine and mouse peripheral nerves (PN) but not with other neural and non-neural tissues. Immunohistochemical analysis showed immunoreactivity for the IgG in the compact myelin of PN. We constructed a human sciatic nerve cDNA library and screened it using the patient's IgG. We identified three independent clones. A homology search of the inserts of these clones revealed that the inserts were homologous to P0 cDNA. However, all the inserts corresponded to the 3'-untranslational region of P0 cDNA. Then, to analyze the 35-kd antigen biochmically, myelin fractions of human and bovine sciatic nerve were prepared. Using SDS-polyacrylamide gel electrophresis, the 35-kd antigen was purified from the crude myelin fraction. When the immunoreactivities of the 35-kd antigen for the patient's IgG and monoclonal anti-P0 antibody were compared with those of protein P0 for these antibodies, the 35-kd antigen reacted with both the antibodies, but P0 reacted with only monoclonal anti-P0 antibody. These results indicate the possibility of the 35-kd antigen being an isoform of P0. However, the presence of these autoantibodies against the 35-kd antigen seems to be of little pathological significance, because circulating autoantibodies against the antigen were also found in the sera of patients with malignant lymphoma without associated peripheral neuropathy.