Autoantibodies of the IgM Class against a Human Myeloma Protein IgE(DES). II. Specificity

Publisher Website
Google Scholar
Abstract
Five different monoclonal IgE proteins, papain and pepsin fragments of myeloma protein IgE(DES) and particle-counting immunoassay were used to study in detail the epitope(s) of IgE(DES) involved in the agglutination with IgM anti-IgE(DES) antibodies. The specificity of these autoantibodies was restricted to IgE(DES) as they did not react with latex particles coated with four other IgE myeloma proteins. Antibodies reactive with latex-IgE other than latex-IgE(DES), when present, were also of restricted specificity as shown by criss-cross absorption experiments. These differences between IgE myeloma proteins could not be attributed to the light chain type nor to the Em(l)-allotype. The epitope(s) of IgE(DES) participating in the reaction was heat-resistant (56 °C, 2 h) and localized in the pepsin F(ab′)2ε fragment, but was absent in the papain Fcε and Fabε fragments. Further degradation by pepsin of the F(ab′)2ε fragment (molecular weight 145,000 daltons) to 5Sε (90,000 daltons) and FcεXXX fragments (30,000 daltons) destroyed the reacting epitope. These results indicate that the IgM antibodies were not directed against k chain or idiotypic determinants of IgE(DES), but to some epitope(s) in the undegraded hinge region. Therefore, it seems that some kind of antigenic heterogeneity, perhaps related to the carbohydrate moieties, is present in IgE myeloma proteins besides the known idiotypic, allotypic and isotypic ones.

This publication has 12 references indexed in Scilit: