Dataset Information

Discovery of a unique Ig heavy-chain isotype (IgT) in rainbow trout: Implications for a distinctive B cell developmental pathway in teleost fish.

ABSTRACT: During the analysis of Ig superfamily members within the available rainbow trout (Oncorhynchus mykiss) EST gene index, we identified a unique Ig heavy-chain (IgH) isotype. cDNAs encoding this isotype are composed of a typical IgH leader sequence and a VDJ rearranged segment followed by four Ig superfamily C-1 domains represented as either membrane-bound or secretory versions. Because teleost fish were previously thought to encode and express only two IgH isotypes (IgM and IgD) for their humoral immune repertoire, we isolated all three cDNA isotypes from a single homozygous trout (OSU-142) to confirm that all three are indeed independent isotypes. Bioinformatic and phylogenetic analysis indicates that this previously undescribed divergent isotype is restricted to bony fish, thus we have named this isotype "IgT" (tau) for teleost fish. Genomic sequence analysis of an OSU-142 bacterial artificial chromosome (BAC) clone positive for all three IgH isotypes revealed that IgT utilizes the standard rainbow trout V(H) families, but surprisingly, the IgT isotype possesses its own exclusive set of D(H) and J(H) elements for the generation of diversity. The IgT D and J segments and tau constant (C) region genes are located upstream of the D and J elements for IgM, representing a genomic IgH architecture that has not been observed in any other vertebrate class. All three isotypes are primarily expressed in the spleen and pronephros (bone marrow equivalent), and ontogenically, expression of IgT is present 4 d before hatching in developing embryos.

SUBMITTER: Hansen JD

PROVIDER: S-EPMC1100771 | biostudies-literature | 2005 May

REPOSITORIES: biostudies-literature

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Discovery of a unique Ig heavy-chain isotype (IgT) in rainbow trout: Implications for a distinctive B cell developmental pathway in teleost fish.

Hansen John D JD Landis Eric D ED Phillips Ruth B RB

Proceedings of the National Academy of Sciences of the United States of America 20050429 19

During the analysis of Ig superfamily members within the available rainbow trout (Oncorhynchus mykiss) EST gene index, we identified a unique Ig heavy-chain (IgH) isotype. cDNAs encoding this isotype are composed of a typical IgH leader sequence and a VDJ rearranged segment followed by four Ig superfamily C-1 domains represented as either membrane-bound or secretory versions. Because teleost fish were previously thought to encode and express only two IgH isotypes (IgM and IgD) for their humoral ...[more]

PMID: 15863615

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Project description:Upon infection, B-lymphocytes expressing antibodies specific for the intruding pathogen develop clonal responses triggered by pathogen recognition via the B-cell receptor. The constant region of antibodies produced by such responding clones dictates their functional properties. In teleost fish, the clonal structure of B-cell responses and the respective contribution of the three isotypes IgM, IgD and IgT remain unknown. The expression of IgM and IgT are mutually exclusive, leading to the existence of two B-cell subsets expressing either both IgM and IgD or only IgT. Here, we undertook a comprehensive analysis of the variable heavy chain (VH) domain repertoires of the IgM, IgD and IgT in spleen of homozygous isogenic rainbow trout (Onchorhynchus mykiss) before, and after challenge with a rhabdovirus, the Viral Hemorrhagic Septicemia Virus (VHSV), using CDR3-length spectratyping and pyrosequencing of immunoglobulin (Ig) transcripts. In healthy fish, we observed distinct repertoires for IgM, IgD and IgT, respectively, with a few amplified ? and ? junctions, suggesting the presence of IgM- and IgT-secreting cells in the spleen. In infected animals, we detected complex and highly diverse IgM responses involving all VH subgroups, and dominated by a few large public and private clones. A lower number of robust clonal responses involving only a few VH were detected for the mucosal IgT, indicating that both IgM(+) and IgT(+) spleen B cells responded to systemic infection but at different degrees. In contrast, the IgD response to the infection was faint. Although fish IgD and IgT present different structural features and evolutionary origin compared to mammalian IgD and IgA, respectively, their implication in the B-cell response evokes these mouse and human counterparts. Thus, it appears that the general properties of antibody responses were already in place in common ancestors of fish and mammals, and were globally conserved during evolution with possible functional convergences.

Dataset Information

Discovery of a unique Ig heavy-chain isotype (IgT) in rainbow trout: Implications for a distinctive B cell developmental pathway in teleost fish.

Publications

Discovery of a unique Ig heavy-chain isotype (IgT) in rainbow trout: Implications for a distinctive B cell developmental pathway in teleost fish.

Similar Datasets

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