Diversity of Immunoglobulin (Ig) Isotypes and the Role of Activation-Induced Cytidine Deaminase (AID) in Fish

• Published in: Molecular biotechnology Vol. 60; no. 6; pp. 435 - 453
• Main Authors: Patel, Bhakti, Banerjee, Rajanya, Samanta, Mrinal, Das, Surajit
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.06.2018; Springer Nature B.V
• Subjects: Activation-induced cytidine deaminase; active sites; adaptive immunity; Adaptive systems; Animals; Antibody Diversity; B-Cell Activating Factor - immunology; B-lymphocytes; Biochemistry; Biological Techniques; Biotechnology; BLyS protein; Catalysis; Cell activation; Cell Biology; Chemistry; Chemistry and Materials Science; Class switching; Cytidine deaminase; Cytidine Deaminase - physiology; Evolution, Molecular; Fish; Fishes - genetics; Fishes - immunology; genes; Genes, Immunoglobulin Heavy Chain; Heavy chains; Human Genetics; Humans; Immune system; Immunoglobulin Class Switching; Immunoglobulin Isotypes - genetics; Immunoglobulin Isotypes - metabolism; Immunoglobulins; Isotypes; ligands; Loci; Lymphocytes B; Lymphocytes T; Mice; paraphyly; Protein Science; Receptors, Antigen - immunology; Receptors, Pattern Recognition - immunology; Recombination; Review; Switching; Vertebrates; Activation-induced deaminase (AID); B cell activating factor (BAFF); Immunoglobulins; Isotype switching; Teleosts
• ISSN: 1073-6085; 1559-0305; 1559-0305
• 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.