Conventional IgG is composed of heavy and light chains. The light chain has one variable region (VL) and one constant region (CL) domain, whereas the heavy chain has one variable region (VH) and three constant region domains (CH1, CH2 and CH3). Single domain antibody (sdAb) is a kind of antibody that is composed of a variable domain of heavy chain and devoid of the light chain completely. Due to its small size, it is also called as nanobody. Although the sdAb has a simple structure, it can exhibit a comparable even better antigen-binding affinity than conventional antibody. Compared with conventional antibody, the small size, high stability and simplicity in recombinant expression are representative advantages of sdAb. In recent years, scientists are becoming increasingly interested in the roles of sdAb in fundamental biomedical research and clinical application. In this review, we summarized the structural features, physicochemical properties, screening strategies and recent advances in application of sdAb.
传统IgG 抗体分子一般由轻链和重链组成，轻链包含1 个可变区 (VL) 和1 个恒定区 (CL)，重链包含1 个可变区 (VH) 和3 个恒定区 (CH1，CH2，CH3)。单域抗体 (Single domain antibody，sdAb)，是指缺失抗体轻链而只有重链可变区的一类抗体，因其分子量小，也被称为纳米抗体 (Nanobody)。20 世纪90 年代，单域抗体最早在骆驼科动物中被发现，之后在护士鲨、大星鲨和鳐鱼等软骨鱼纲动物中也发现了类似的抗体。单域抗体虽然结构简单，但仍然可以达到与传统抗体相当甚至更高的与特异抗原结合的亲和力。相比于传统抗体，单域抗体具有分子量小、稳定性强、易于重组表达等优点。近年来在生物学基础研究和医学临床应用方面均备受关注并被广泛应用。文中将从单域抗体的结构特征、理化性质、筛选方法及其在生物医学领域的重要应用进展进行综述。.
Keywords: camelids; heavy-chain antibody; nanobody; single-domain antibody.