Department of Biochemistry, Faculty of Medicine, Saitama Medical University, Saitama, Japan.
Clin Chim Acta. 2011 May 12;412(11-12):843-9. doi: 10.1016/j.cca.2011.03.007. Epub 2011 Mar 15.
Immunoglobulin light chain (IgLC) is a component of antibodies, but its free form is observed in the circulation, which originates from 10 to 40% excess synthesis over heavy chain in B cells. Complete antibodies function as a defined tetramer structure unit, H2L2; thus, separation of heavy and light chains results in considerable or complete loss of antigen-binding ability. Free IgLC has been considered as an inconsequential spillover during antibody assembly because, unlike heavy chain, neither effector functions such as complement activation nor specific-receptor binding has been identified in IgLCs. Free IgLC in sera and cerebrospinal fluids increases in inflammatory diseases such as autoimmune diseases and infections, presumably as a result of B-cell activation. This may be just a concomitant event during elevated disease activity, but recent findings suggest that free IgLC is involved in a wide range of immunological phenomena as a signaling effector or an anti-inflammatory molecule. These effects are likely to be intrinsic to IgLC. In this review, we attempt to give a comprehensive view about the biological roles of free IgLC together with the gene expression, secretion, antigen-binding ability, and its metabolic characteristics.
免疫球蛋白轻链 (IgLC) 是抗体的组成部分，但在循环中观察到其游离形式，它来源于 B 细胞中重链过量合成的 10%至 40%。完整的抗体作为一个定义的四聚体结构单元 H2L2 发挥作用；因此，重链和轻链的分离会导致抗原结合能力的显著或完全丧失。游离 IgLC 被认为是抗体组装过程中的一种无关紧要的溢出物，因为与重链不同，游离 IgLC 既没有补体激活等效应功能，也没有特异性受体结合。血清和脑脊液中的游离 IgLC 在自身免疫性疾病和感染等炎症性疾病中增加，推测是由于 B 细胞激活。这可能只是疾病活动升高期间的伴随事件，但最近的发现表明，游离 IgLC 作为信号效应物或抗炎分子参与广泛的免疫现象。这些影响可能是 IgLC 的固有特性。在这篇综述中，我们试图全面了解游离 IgLC 的生物学作用，包括基因表达、分泌、抗原结合能力及其代谢特征。
