Glycation of Human IgG Induces Structural Alterations Leading to Changes in its Interaction with Anti-IgG

Background: Glycation of proteins is a non-enzymatic spontaneous process that occurs in diabetes mellitus and aging, altering the structure and function of proteins. IgG undergoes glycation leading to changes in its reactivity to antigen and fixation of complement.   Objective: This study aimed at revealing the effect of glycation on the interaction of IgG with anti-IgG using electroimmunoassay.   Methods: Purified human IgG was glycated with different concentrations of glucose and different periods of treatment. Glycation was measured using thiobarbituric acid reaction. Glycated and non-glycated IgG were subjected to electroimmunoassay, and the height of the precipitated rings were measured and compared.   Results: The results showed that IgG was glycated in vitro and the level of glycation was dependent on the glucose concentration and duration of treatment with glucose. The height of glycated IgG peaks formed in the electroimmunoassay was significantly lower than those of nonglycated IgG (   p < 0.01). Conclusion: The results indicated that in vitro glycation of IgG leads to structural changes altering its mobility in the electroimmunoassay. Moreover, it suggests that this alteration may cause the weakness of its interaction with anti-IgG. This phenomenon may play a role in the susceptibility of diabetic patients to infection.