In vitro Glycation of Human IgG and Its Effect on Interaction with Anti-IgG

Non-enzymatic glycosylation of proteins is one of the key mechanisms in the pathogenesis of diabetic complications. Glycation of IgG is of special interest due to its possible influence on the functionality of immunoglobulins and overall immuno-competence. The aim of this study was to clarify more details of in vitro glycation of IgG and to study the effect of this modification on its interation with anti-IgG. Purified human IgG was glycated in the presence of 50 and 100 mM glucose. Glycation was measured using spectrophotometric thiobarbituric acid method. To study the effect of glycation on interaction with anti IgG the Single Radial Immunodiffusion (SRID) was used and the diameters of precipitation rings of glycated IgG and non-glycated IgG were measured and compared. The results showed that IgG was glycated in presence of 50 and 100 mM glucose at 27 degrees and 37 degrees C and the extent of glycation was dependent on glucose concentration and time of incubation. In higher concentration of glucose and longer period of incubation glycation was higher at 27 degrees C (p<0.01). Similar results were obtained at 37 degrees C.The results of SRID indicated that glycated IgG showed reduced interaction with anti-IgG. The diameters of precipitated rings for glycated IgG were significantly lower than those of non-glycated IgG (p < 0.01). It can be concluded that modification that occurred in IgG structure due to glycation can be the reason of the reduction of its interaction with anti-IgG.