期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：12
页码：5682-5686
DOI：10.1073/pnas.74.12.5682
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The effects of antigen binding on IgM antibody conformation were investigated by measuring the immunological reactivity of the Fc-bound J polypeptide. For such measurements anti-azophenyl-beta-D-lactoside and anti-azobenzenearsonate IgM antibodies were examined in a J chain radioimmunoassay before and after complexing with various hapten-conjugates. The assays showed that (i) the accessibility of J chain determinants is very limited in uncomplexed IgM and (ii) their accessibility is significantly enhanced in the presence of an excess of specific antigen. In both antibody systems, enhanced J chain exposure was achieved with the homologous multi-hapten-substituted antigen (1.9-fold), with a small multivalent antigen in which three to four hapten groups were coupled to a heterologous carrier (1.55-fold), and with monohapten-substituted antigen (1.4-fold). Because the J chain is located in the terminal CH4 Fc domains, these data provide direct evidence that a change in Fc conformation is induced by the binding of antigen to the distant Fab combining sites. Moreover, the data indicate that the changes in J chain exposure do not depend on crosslinking by antigen, but can be induced by the interaction of antigen at individual IgM combining sites.
