The constant region affects antigen binding of antibodies to DNA by altering secondary structure

Yumin Xia, Alena Janda, Ertan Eryilmaz, Arturo Casadevall, Chaim Putterman

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31 Scopus citations


We previously demonstrated an important role of the constant region in the pathogenicity of anti-DNA antibodies. To determine the mechanisms by which the constant region affects autoantibody binding, a panel of isotype-switch variants (IgG1, IgG2a, IgG2b) was generated from the murine PL9-11 IgG3 autoantibody. The affinity of the PL9-11 antibody panel for histone was measured by surface plasmon resonance (SPR). Tryptophan fluorescence was used to determine wavelength shifts of the antibody panel upon binding to DNA and histone. Finally, circular dichroism spectroscopy was used to measure changes in secondary structure. SPR analysis revealed significant differences in histone binding affinity between members of the PL9-11 panel. The wavelength shifts of tryptophan fluorescence emission were found to be dependent on the antibody isotype, while circular dichroism analysis determined that changes in antibody secondary structure content differed between isotypes upon antigen binding. Thus, the antigen binding affinity is dependent on the particular constant region expressed. Moreover, the effects of antibody binding to antigen were also constant region dependent. Alteration of secondary structures influenced by constant regions may explain differences in fine specificity of anti-DNA antibodies between antibodies with similar variable regions, as well as cross-reactivity of anti-DNA antibodies with non-DNA antigens.

Original languageEnglish
Pages (from-to)28-37
Number of pages10
JournalMolecular Immunology
Issue number1-2
StatePublished - Nov 2013
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by grants from the NIH ( AR048692 and DK090319 to C. Putterman, and HL059842 , AI033774 , AI033142 , AI052733 to A. Casadevall), and the Center for AIDS Research at the Albert Einstein College of Medicine (A. Casadevall). A.J. received support from the Institutional AIDS Training Grant T32-AI007501 as well the NIH MSTP Training Grant T32-GM007288 . We thank Dr. Huiyong Cheng and Dr. Sergei Khrapunov (Department of Biochemistry, Albert Einstein College of Medicine) for help with the Biacore analysis and tryptophan fluorescence measurement, and Dr. Ariel Lewis (Department of Physiology and Biophysics, Albert Einstein College of Medicine) for assistance in the operation of circular dichroism machine.


  • Anti-DNA antibodies
  • Antigen-antibody interactions
  • Systemic lupus erythematosus


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