Changes in avidity and specificity of IgG during electro-oxidation. Relevance of binding of antibodies to β2-GPI

Abstract The immune response may be changed due to altered proteins or modifications of immunoglobulins, including oxidative processes. The susceptibility to oxidative modifications depends greatly on amino-acid moiety composition due to chemical characteristics (instability) of their side-chains. Initial steps of oxidation may change the specificity and avidity of immunoglobulins due to chemical alteration of the hypervariable region. The oxidation of antibodies increases the hydrophilic nature of the paratopes and makes them more susceptible for the binding to cationic surfaces even without the strong surface-to-surface fitting. The electro-oxidation of IgG significantly changes the immunoreactivity and specificity of IgG fractions, regardless of the initial immunoreactivity to a specific autoantigen also in healthy persons. Data are presented on changes in the immunoreactivity as well as the avidity of antibodies against β2-glycoprotein I after being exposed to direct current. ELISA measurements showed increased reactivity of anti-β2-glycoprotein I antibodies at the beginning and various, fluctuating results after prolonged exposure to electro-oxidation. Inter-individual differences in chemical stability of immunoglobulins and patient's antioxidative status may influence the range of their alterations and their impact on health/disease balance.