Ferrous Ions and Reactive Oxygen Species Increase Antigen-binding and Anti-inflammatory Activities of Immunoglobulin G

Tchavdar L Vassilev,Jordan D Dimitrov,Nina D Ivanovska,Srinivas V Kaveri,Virjinia R Doltchinkova,Sébastien Lacroix-Desmazes

doi:10.1074/jbc.m509190200

Tchavdar L Vassilev, Jordan D Dimitrov + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m509190200

Copy DOI

Abstract

Polyspecific antibodies represent a first line of defense against infection and regulate inflammation, properties hypothesized to rely on their ability to interact with multiple antigens. We demonstrated that IgG exposure to pro-oxidative ferrous ions or to reactive oxygen species enhances paratope flexibility and hydrophobicity, leading to expansion of the spectrum of recognized antigens, regulation of cell proliferation, and protection in experimental sepsis. We propose that ferrous ions, released from transferrin and ferritin at sites of inflammation, synergize with reactive oxygen species to modify the immunoglobulins present in the surrounding microenvironment, thus quenching pro-inflammatory signals, while facilitating neutralization of pathogens.

Highlights

An antibody molecule that relies on the use of active site flexibility for antigen binding is usually capable of accommodating a large number of structurally unrelated antigens (2, 8 –10); i.e. such an antibody is polyspecific
The polyspecificity of a monoclonal mouse IgG (Z2) specific for mouse IgG2a increased upon incubation with Fe(II), binding to their target antigens of immune human polyclonal IgG (pIgG) directed to tetanus toxoid and diphtheria toxoid, and of a human monoclonal IgG directed to cytomegalovirus (Fig. 1A) were not modified, indicating that not all IgG antibodies were sensitive to the presence of ferrous ions
Several lines of evidence ruled out the possibility that the observed effects were caused by Fe(II) ion-induced immunoglobulin denaturation: (i) high performance liquid chromatography analysis of pIgG incubated in the presence of 0.01, 0.1, or 1 mM ferrous ions did not show significant deviations in the chromatographic profiles compared with those of native pIgG, demonstrating that the treatment did not result in the formation of IgG aggregates; (ii) Fe(II)-exposed pIgG did not activate the complement; (iii) not all IgG molecules were sensitive to Fe(II), as antibodies generated after repeated immunizations were not affected by the ferrous ions; (iv) despite changes in antigen-binding activity, Fe(II)-exposed monoclonal antibody retained its binding affinity

Summary

Introduction

An antibody molecule that relies on the use of active site flexibility for antigen binding (according to the last two models) is usually capable of accommodating a large number of structurally unrelated antigens (2, 8 –10); i.e. such an antibody is polyspecific. Exposure to Fe(II) Increases Antigen-binding Activity of Immunoglobulin G—Incubation of human polyclonal IgG (pIgG) in the presence of 1 mM ferrous ions (Fe2ϩ) resulted in a significant increase in reactivity with self (Fig. 1, A and C, and supplemental Fig. S1A) and with bacterial (Fig. 1B) antigens, as well as with F(abЈ)2 fragments of pIgG (Fig. 1D).

Results

Conclusion