Patel Bhakti, Banerjee Rajanya, Samanta Mrinal, Das Surajit
Laboratory of Environmental Microbiology and Ecology (LEnME), Department of Life Science, National Institute of Technology, Rourkela, Odisha, 769 008, India.
Immunology Laboratory, Fish Health Management Division, ICAR-Central Institute of Freshwater Aquaculture, Kausalyaganga, Bhubaneswar, Odisha, 751 002, India.
Mol Biotechnol. 2018 Jun;60(6):435-453. doi: 10.1007/s12033-018-0081-8.
The disparate diversity in immunoglobulin (Ig) repertoire has been a subject of fascination since the emergence of prototypic adaptive immune system in vertebrates. The carboxy terminus region of activation-induced cytidine deaminase (AID) has been well established in tetrapod lineage and is crucial for its function in class switch recombination (CSR) event of Ig diversification. The absence of CSR in the paraphyletic group of fish is probably due to changes in catalytic domain of AID and lack of cis-elements in IgH locus. Therefore, understanding the arrangement of Ig genes in IgH locus and functional facets of fish AID opens up new realms of unravelling the alternative mechanisms of isotype switching and antibody diversity. Further, the teleost AID has been recently reported to have potential of catalyzing CSR in mammalian B cells by complementing AID deficiency in them. In that context, the present review focuses on the recent advances regarding the generation of diversity in Ig repertoire in the absence of AID-regulated class switching in teleosts and the possible role of T cell-independent pathway involving B cell activating factor and a proliferation-inducing ligand in activation of CSR machinery.
自脊椎动物中出现典型的适应性免疫系统以来，免疫球蛋白（Ig）库中截然不同的多样性一直是一个令人着迷的课题。激活诱导的胞苷脱氨酶（AID）的羧基末端区域在四足动物谱系中已得到充分证实，并且对其在Ig多样化的类别转换重组（CSR）事件中的功能至关重要。鱼类并系群中缺乏CSR可能是由于AID催化结构域的变化以及IgH基因座中顺式元件的缺失。因此，了解IgH基因座中Ig基因的排列以及鱼类AID的功能方面，为揭示同种型转换和抗体多样性的替代机制开辟了新领域。此外，最近有报道称硬骨鱼AID通过补充哺乳动物B细胞中的AID缺陷，具有催化其CSR的潜力。在此背景下，本综述重点关注硬骨鱼在缺乏AID调节的类别转换情况下Ig库多样性产生的最新进展，以及涉及B细胞激活因子和增殖诱导配体的T细胞非依赖性途径在激活CSR机制中的可能作用。
