Three New Cross-Reacting Idiotopes as Markers for the Products of Two Distinct Human VH3 Genes Expressed in the Early Repertoire

This article describes characterization of three new cross-reacting idiotopes, as recognized by mouse MoAbs, on human antibodies utilizing VH3 genes that are expressed in the early repertoire. Two of the mouse MoAbs (3H7 and 3H1) were raised against a human MoAb utilizing the DP47 (VH26) VH3 gene, whilst the third (7B4) was raised against a DP46 (GLSJ2) gene product. Evidence for the anti-idiotypic specificity of the mouse MoAbs was provided by their reactivity with the immunizing IgM, but not with Fcα, and by their specific inhibition of the binding between each immunizing antibody and its antigen. The three anti-idiotypic MoAbs were shown to be VH-specific reagents by the independence of their reactivity upon the L-chain type, or the untigenic specificity of the human MoAbs tested. Specificity of each mouse MoAb for VH3 gene-products was demonstrated by its sole cross-reactivity with VH3 proteins. Each anti-Id had a different reactivity pattern with a panel of MoAbs utilizing different VH3 genes. By relating the VH sequences of the tested VH3 proteins to their germline counterparts, 3H7 and 3H1 appeared to be specific for DP47-encoded proteins, although 3H1 had weak cross-reactivities with a few other VH3 gene-products. 7B4 appeared to be specific for antibodies utilizing DP46-related genes. Both 3H7 and 3H1 were also completely different to B6 and D12, two previously described MoAbs that also recognize VH3 proteins. Although 7B4 was similar to B6 and D12 in its binding to DP46-related gene products, B6 and D12 additionally recognized non DP46-related proteins and were thus different to 7B4.