Variable region isotypes

A contribution of the constant region of a polypeptide chain to an idiotypic determinant is conceivable, but idiotypic differences among proteins must reflect differences in the variable regions. Isotypic and allotypic antigenic determinants similarly reflect particular amino acid sequences, which in many instances have been defined. 

Anti-dsDNA Antibodies Are Antigen-Driven. There is evidence that variable regions of both heavy and light chains of both murine and human monoclonal anti-dsDNA antibodies are produced after an affinity maturation process via isotype switching, clonal selection, and somatic mutation (D5, D9, Wll, C16, V3). These findings suggest that anti-dsDNA antibodies are produced by an... 

A B-lymphocyte can simultaneously express membrane immunoglobulin as IgM (monomeric) or IgD with the same variable region (i.e., antigen-binding site). The B-lymphocyte then can secrete different isotypes [e.g., IgM... 

GSR occurs in the Ig heavy-chain locus in the G (constant) domain located downstream of the V(D)J variable region (Fig. 1). Eight different Gh regions encode unique isotypes IgM, IgD, 4 distinct IgG, IgE, or IgA. Initially, mature B cells translate the IgH locus using the most upstream exon G to produce IgM that is expressed as a low-affinity membrane bound and secreted isotype. The expression of the G heavy chain is accomplished by mRNA splicing. Each of the other six G regions contains a cryptic promoter and repetitive switch region (S) located 5 of the exon... 

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