Immunoglobulins in teleosts

AbstractImmunoglobulins are glycoproteins which are produced as membrane-bound receptors on B-cells or in a secreted form, known as antibodies. In teleosts, three immunoglobulin isotypes, IgM, IgT, and IgD, are present, each comprising two identical heavy and two identical light polypeptide chains. The basic mechanisms for generation of immunoglobulin diversity are similar in teleosts and higher vertebrates. The B-cell pre-immune repertoire is diversified by VDJ recombination, junctional flexibility, addition of nucleotides, and combinatorial association of light and heavy chains, while the post-immune repertoire undergoes somatic hypermutation during clonal expansion. Typically, the teleost immunoglobulin heavy chain gene complex has a modified translocon arrangement where the D τ–Jτ–Cτ cluster of IgT is generally located between the variable heavy chain (VH) region and the Dμ/δ–Jμ/δ–Cμ–Cδ gene segments, or within the set of VH gene segments. However, multiple genome duplication and deletion events and loss of some individual genes through evolution has c omplicated the IgH gene organization. The IgH gene arrangement allows the expression of either IgT or IgM/IgD. Alternative splicing is responsible for the regulation of IgM/IgD expression and the secreted versus transmembrane forms of IgT, IgD, and IgM. The overall structure of IgM and IgT is usuall y conserved across species, whereas IgD has a large variety of structures. IgM is the main effector molecul...

Source: Immunogenetics - January 13, 2021 Category: Genetics & Stem Cells Source Type: research