Markedly increased vitamin B12 concentrations attributable to IgG-IgM-vitamin B12 immune complexes
Markedly increased vitamin B12 concentrations attributable to IgG-IgM-vitamin B12 immune complexes
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DOI：
10.1373/clinchem.2006.073882
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发表时间：
2006-11-01
影响因子：
9.3
通讯作者：
Horne, McDonald K., III
中科院分区：
文献类型：
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作者：
Bowen, Raffick A. R.;Drake, Steven K.;Horne, McDonald K., III
背景：据报道，患有肝病、播散性肿瘤、骨髓增殖性疾病和嗜酸性粒细胞增多综合征的患者血清维生素 B-12 浓度较高。我们最近发现一名没有这些基础疾病的患者体内维生素 B-12 浓度异常升高。方法：采用亲和和尺寸排阻色谱、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳 (SDS-PAGE)、基质辅助激光解吸/电离飞行时间质谱 (MALDI-TOF MS) 和 ELISA 方法确定该患者血清中维生素 B-12 浓度升高的原因。从 2 名表面健康的志愿者和 2 名最近接受维生素 B-12 治疗贫血的患者的蛋白质 G 柱洗脱物中，维生素 B-12 浓度 < 74 pmol/L，而从患者的蛋白质 G 柱洗脱物中维生素 B-12 浓度为 7380 pmol/L。患者血清中维生素 B-12 结合蛋白的尺寸排阻色谱洗脱图显示存在异常的维生素 B-12 结合蛋白。在还原条件下，对 Protein G 柱的浓缩洗脱液进行 SDS-PAGE 分析，显示出一条表观分子量为 76 kDa 的附加条带，而对照柱洗脱液中不存在该条带。 MALDI-TOF MS 将该条带鉴定为 IgM 重链。通过使用改良的 ELISA，我们确定患者洗出液中存在的 IgM 与 IgG 相关，形成 IgG-IgM 免疫复合物。结论：该病例表明，由于由 IgG、IgM 和维生素 B-12 组成的免疫复合物，患者的维生素 B-12 浓度显着升高，并说明了可用于识别这种情况的技术。 (c) 2006 年美国临床化学协会。
Background: High serum vitamin B-12 concentrations have been reported in patients with hepatic disease, disseminated neoplasia, myeloproliferative disorders, and hypereosinophilic syndromes. We recently discovered an extraordinarily increased vitamin B-12 concentration in a patient without these underlying conditions.Methods: Affinity and size-exclusion chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and ELISA methods were used to determine the cause of the increased vitamin B-12 concentrations in this patient's serum.Results: The protein G column eluates from 2 apparently healthy volunteers and 2 patients with recent vitamin B-12 treatment for anemia had vitamin B-12 concentrations of < 74 pmol/L, whereas the vitamin B-12 concentration in the protein G column eluate from the patient was 7380 pmol/L. The elution profile from size-exclusion chromatography of vitamin B-12-binding proteins in the patient's serum revealed an abnormal vitamin-B-12-binding protein. SDS-PAGE analysis of the concentrated eluates from the protein G column, under reducing conditions, revealed an additional band with an apparent molecular mass of 76 kDa, which was not present in control column eluates. MALDI-TOF MS identified this band as an IgM heavy chain. By use of a modified ELISA, we determined that the IgM present in the patient's eluates was associated with the IgG to form IgG-IgM immune complexes.Conclusions: This case demonstrates the unusual circumstance of a patient with markedly increased vitamin B-12 concentrations attributed to immune complexes composed of IgG, IgM, and vitamin B-12 and illustrates techniques that can be used to identify this occurrence. (c) 2006 American Association for Clinical Chemistry.