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A ranavirus-induced thymus cDNA library was constructed from Chinese giant salamander, the largest extant amphibian species. Among the 137 putative immune-related genes derived from this library, these molecules received particular focus: immunoglobulin heavy chains (IgM, IgD, and IgY), IFN-inducible protein 6 (IFI6), and T cell receptor beta chain (TCRβ). Several unusual features were uncovered: IgD displays a structure pattern distinct from those described for other amphibians by having only four constant domains plus a hinge region. A unique IgY form (IgY(ΔFc)), previously undescribed in amphibians, is present in serum. Alternative splicing is observed to generate IgH diversification. IFI6 is newly-identified in amphibians, which occurs in two forms divergent in subcelluar distribution and antiviral activity. TCRβ immunoscope profile follows the typical vertebrate pattern, implying a polyclonal T cell repertoire. Collectively, the pioneering survey of ranavirus-induced thymus cDNA library from Chinese giant salamander reveals immune components and characteristics in this primitive amphibian. [ABSTRACT FROM AUTHOR]

Highlights: [•] First characterization of MHC alleles in the Chinese giant salamander Andrias davidianus. [•] Anda-MHC genes exhibit high allelic diversity maintained by positive selection acting on the PBR. [•] Two isoforms (full-length and splice transcripts) of Anda-MHC coexist in various tissues. [•] Anda-MHC variants display similar subcellular localization with the full-length transcripts. [•] Anda-MHC gene expression was increased during viral infection. [Copyright &y& Elsevier]