Antibodies have proven to be central in the development of diagnostic methods over decades, moving from polyclonal antibodies to the milestone development of monoclonal antibodies. Although monoclonal antibodies play a valuable role in diagnosis, their production is technically demanding and can be expensive. The large size of monoclonal antibodies (150 kDa) makes their re-engineering using recombinant methods a challenge. Single-domain antibodies, such as "nanobodies," are a relatively new class of diagnostic probes that originated serendipitously during the assay of camel serum. The immune system of the camelid family (camels, llamas, and alpacas) has evolved uniquely to produce heavy-chain antibodies that contain a single monomeric variable antibody domain in a smaller functional unit of 12-15 kDa. Interestingly, the same biological phenomenon is observed in sharks. Since a single-domain antibody molecule is smaller than a conventional mammalian antibody, recombinant engineering and protein expression in vitro using bacterial production systems are much simpler. The entire gene encoding such an antibody can be cloned and expressed in vitro. Single-domain antibodies are very stable and heat-resistant, and hence do not require cold storage, especially when incorporated into a diagnostic kit. Their simple genetic structure allows easy re-engineering of the protein to introduce new antigen-binding characteristics or attach labels. Here, we review the applications of single-domain antibodies in laboratory diagnosis and discuss the future potential in this area.

中文翻译：

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单域抗体（“纳米抗体”）在实验室诊断中的应用。

几十年来，抗体已被证明是诊断方法发展的核心，从多克隆抗体发展到单克隆抗体的里程碑式发展。尽管单克隆抗体在诊断中发挥着重要作用，但它们的生产技术要求高且价格昂贵。单克隆抗体的大尺寸 (150 kDa) 使得使用重组方法对其进行重新设计成为一项挑战。单域抗体，例如“纳米抗体”，是一类相对较新的诊断探针，在骆驼血清分析过程中偶然出现。骆驼科动物（骆驼、美洲驼和羊驼）的免疫系统经过独特的进化，可以产生重链抗体，这些抗体在 12-15 kDa 的较小功能单元中包含单个单体可变抗体域。有趣的是，在鲨鱼身上也观察到了同样的生物现象。由于单域抗体分子比常规哺乳动物抗体小，重组工程和蛋白质表达在体外使用细菌生产系统要简单得多。可以在体外克隆和表达编码这种抗体的整个基因。单域抗体非常稳定且耐热，因此不需要冷藏，尤其是在纳入诊断试剂盒时。它们简单的遗传结构允许轻松重新设计蛋白质以引入新的抗原结合特征或附加标签。在这里，我们回顾了单域抗体在实验室诊断中的应用，并讨论了该领域的未来潜力。