Detection and diagnostic utility of paraproteins in body fluids

研究各种体液中的免疫球蛋白，特别是血清、尿液和脑脊液中的免疫球蛋白，对于了解各种疾病的发病机制以及诊断和监测疾病具有重要意义。蛋白质电泳法(PEP)和免疫固定电泳法(IFE)是识别蛋白质异常和检测体液中异常免疫球蛋白(副蛋白)的关键技术。副蛋白是浆细胞克隆性或寡克隆性增殖的产物，因此可能代表完整的免疫球蛋白、游离重链和/或免疫球蛋白的游离轻链。然而，假副蛋白(P-蛋白)的出现会阻碍对副蛋白的正确鉴定。P-蛋白是通常存在的蛋白，在蛋白电泳图上模仿M-蛋白。在过去的几个月里，我们观察到了几个在现有文献中没有描述的尿P蛋白病例。综合运用各种分析技术(如琼脂糖凝胶和聚丙烯酰胺凝胶电泳法、免疫电泳法和质谱仪)，我们现在正在对这些P-蛋白进行全面鉴定。 在一项合作研究中，我们调查了硅胶乳房假体与血清副蛋白的出现之间的可能联系，作为良性或恶性淋巴增生性疾病的指标，特别是意义不明的良性单克隆性伽马病(MGUS)和多发性骨髓瘤(MM)。先前的研究表明，硅胶植入物的女性存在包括副蛋白在内的血清蛋白异常，但没有对结缔组织病(CTD)的存在进行控制。在我们在三级护理学术中心进行的回溯性病例对照研究中，我们评估了在这样一个人群中血清蛋白，包括副蛋白的可能变化。在初步研究中，对74名接受硅胶植入物的女性和74名年龄和CTD匹配的未植入硅胶植入物的女性进行了评估；其他组用于进一步的比较。采用常规血清蛋白测定、高敏蛋白电泳法和免疫固定电泳法检测副蛋白。与未植入硅胶植入物的女性相比，植入硅胶植入物的女性，无论是否有CTD，其血清总蛋白和α-1、α-2、β、γ球蛋白和免疫球蛋白水平均显著降低。然而，硅胶植入物和CTD组的副蛋白血症的发生率(9.5%)和年龄与CTD相匹配的未植入硅胶组的副蛋白血症发生率(5.4%)没有显著差异(优势比1.82，95%可信区间0.51到6.45)。在两组中，副蛋白亚型相似，13名患有副蛋白血症的妇女的临床特征与10名接受硅胶乳房假体、CTD和先前诊断的单克隆性伽玛病的独立人群相似。综上所述，在这项首次对硅胶植入物和CTD患者的血清蛋白进行的综合性研究中，我们没有发现显著增加发生单克隆性丙种球蛋白病的风险。然而，接受硅胶植入物的女性血清球蛋白和免疫球蛋白水平出人意料地低，无论是否有随后的CTD发展。这些发现的原因和临床意义需要进一步调查。 在另一项合作研究中，我们对27年前最初评估的三个WM家族进行了随访研究，调查了家族性Waldenstrom巨球蛋白血症(WM)患者亲属免疫球蛋白异常的临床意义。这项研究是迄今为止对西医家庭进行的最长时间的全面跟踪调查。根据血清蛋白电泳法、免疫固定电泳法和临床资料，在某些家系中，IgM单克隆性丙种球蛋白病似乎是WM易感性的表型标志，并可能具有进展为WM的高风险。免疫球蛋白多克隆病在西医家族中也可能是重要的。这些观察结果需要在更大规模的研究中进行验证，如果得到证实，可能会被用来确定队列(患有IgM单克隆性丙种球蛋白病的亲属)，以用于未来的预防策略。

Study of immunoglobulins in various body fluids, especially in serum, urine and cerebrospinal fluid (CSF), is important for understanding the pathomechanism of a variety of diseases and for diagnosing and monitoring diseases. Protein electrophoresis (PEP) and immunofixation electrophoresis (IFE) are key techniques to identifiy protein abnormalities and to detect abnormal immunoglobulins (paraproteins) in body fluids. The paraproteins are the products of clonal or oligoclonal proliferation of plasma cells and, as such, may represent full immunoglobulins, free heavy chains, and/or free light chains of immunoglobulins. Correct identification of paraproteins can be hampered, however, by the occurrence of pseudoparaproteins (P-proteins). P-proteins are normally occurring proteins that mimic M-proteins in protein electrophoretic patterns. Over the past few months, we have observed several cases of urine P-proteins that had not been described in the existing literature. Using a combination of various analytical techniques (e.g., electrophoresis in agarose and polyacrylamide gel, immunoelectrophoresis, and mass spectrometry), we are now in the process to fully identify these P-proteins. In a collaborative study, we investigated possible associations between silicone breast implants and the occurrence of serum paraproteins as indicators of benign or malignant lymphoproliferative disorders, and, in particular, benign monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM). Prior studies have suggested abnormalities of serum proteins, including paraproteins, in women with silicone implants but did not control for the presence of connective-tissue disease (CTD). In our retrospective case-control study, performed in tertiary-care academic centers, we assessed possible alterations of serum proteins, including paraproteins, in such a population. Seventy-four women with silicone implants who subsequently developed CTD and 74 age- and CTD-matched women without silicone implants were assessed in the primary study; other groups were used for additional comparisons. Routine serum protein determinations and high-sensitivity protein electrophoresis and immunofixation electrophoresis were performed for detection of paraproteins. Women with silicone implants, either with or without CTD, had significantly lower serum total protein and alpha-1, alpha-2, beta, and gamma globulins, and IgG levels compared to those without silicone implants. There was no significant difference, however, in the frequency of paraproteinemia between women with silicone implants and CTD (9.5%) and age- and CTD-matched women without silicone implants (5.4%) (odd ratio 1.82 95% confidence intervals 0.51 to 6.45). Paraprotein isotypes were similar in the two groups and the clinical characteristics of the 13 women with paraproteinemia were comparable to an independent population of 10 women with silicone breast implants, CTD and previously diagnosed monoclonal gammopathies. In summary, in this first comprehensive study of serum proteins in women with silicone implants and CTD we found no substantially increased risk of monoclonal gammopathy. Women with silicone implants, however, had unexpectedly low serum globulin and immunoglobulin levels, with or without the subsequent development of CTD. The causes and clinical implications of these findings require further investigation. In another collaborative study, we investigated the clinical significance of immunoglobulin abnormalities in relatives of familial Waldenstrom macroglobulinemia (WM) patients in a follow-up study of three WM families originally evaluated 27 years previously. This study is the longest comprehensive follow-up of WM families to date. Based on the results of serum protein electrophoresis, immunofixation electrophoresis and clinical data, IgM monoclonal gammopathy seemed to be a phenotypic marker of WM susceptibility in some families and may carry a high risk of progression to WM. IgM polyclonal gammopathy may also be important in WM families. These observations require validation in larger studies and, if confirmed, may be used to identify a cohort (relatives with IgM monoclonal gammopathy) for future prevention strategies.