Chen Changqiang, Chen Peizhan, Fang Xuqian
Department of Clinical Laboratory, Ruijin Hospital North, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Translational Medicine Research Center, Ruijin Hospital North, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
J Clin Lab Anal. 2019 Feb;33(2):e22658. doi: 10.1002/jcla.22658. Epub 2018 Aug 27.
Monoclonal free light chains (FLC) commonly exist in monomeric or dimeric forms but rarely as larger molecules. Little is known about whether polymeric molecules can affect urine protein electrophoresis (UPE) results.
Urine samples were collected from 72 multiple myeloma (MM) patients with Bence Jones protein (BJP). Urine protein and immunofixation electrophoresis were analyzed on Sebia SDS "agarose" gel electrophoresis system (SDS-AGE), and immunoglobulin free light chains were measured on the BNII nephelometric assay.
A type of disulfide-bound FLC dimer shows a pattern shift to the position of the "albumin" band in urine protein electrophoresis in multiple myeloma (MM) patients according to the Sebia agarose gel-based detection system, which was validated by immunofixation, SDS-PAGE, and mass spectrometric methods. Similar cases were found in 21 (29.17%) of 72 MM patients with BJP, and 19 (90.5%) of 21 patients were the lambda type.
These results indicate that BJP with lambda type has a strong tendency to abnormally migrate, which may increase the risk of misinterpretation of protein electrophoresis in clinics. Thus, when the urine protein electrophoresis is inconsistent with the result by nephelometric method, urine protein electrophoresis needs to be repeated on the deduced condition to confirm the essence of the originally identified "albumin."
单克隆游离轻链（FLC）通常以单体或二聚体形式存在，但很少以更大的分子形式存在。关于聚合分子是否会影响尿蛋白电泳（UPE）结果，人们知之甚少。
收集72例伴有本-周蛋白（BJP）的多发性骨髓瘤（MM）患者的尿液样本。在Sebia SDS“琼脂糖”凝胶电泳系统（SDS-AGE）上分析尿蛋白和免疫固定电泳，并在BNII比浊法上检测免疫球蛋白游离轻链。
根据基于Sebia琼脂糖凝胶的检测系统，一种二硫键结合的FLC二聚体在多发性骨髓瘤（MM）患者的尿蛋白电泳中显示出迁移模式向“白蛋白”条带位置的转变，这通过免疫固定、SDS-PAGE和质谱方法得到了验证。在72例伴有BJP的MM患者中的21例（29.17%）发现了类似病例，21例患者中的19例（90.5%）为λ型。
这些结果表明，λ型BJP有很强的异常迁移倾向，这可能会增加临床蛋白质电泳误判的风险。因此，当尿蛋白电泳结果与比浊法结果不一致时，需要在推测的情况下重复进行尿蛋白电泳，以确认最初鉴定的“白蛋白”的本质。
