Endocrine Abstracts

Objective: To evaluate the hydrolytical activity of autoantibodies (Ab) to double-stranded DNA using atomic force microscopy in patients with autoimmune thyroiditis.

Methods: Ab to double-stranded DNA (dsDNA) IgG class were isolated from the serum of patients with autoimmune thyroiditis by DNA-affinity chromatography. Hydrolytical activity of Ab to dsDNA was confirmed by Polyacrylamide Gel Electrophoresi (PAGE). The images of Ab to dsDNA and results of dsDNA’s hydrolysis were recorded by atomic force microscopy (AFM). Two kinds of substrate were used: plasmid DNA PBr –322 for PAGE and chickens erythrocytes chromosomal DNA for AFM.

Results: Usage of AFM allowed to get images of chromosomal DNA from chicken erythrocytes and Ab to dsDNA from patients with autoimmune thyroiditis and to measure molecular’s size and weight. Ab to dsDNA and chromosomal DNA interaction leads to appearance of DNA fragments with low molecular weight via to control samples. This effect explains by hydrolysis of DNA molecule. The number of short DNA fragments directly depends on the length of the reaction. An interaction area between Ab to dsDNA and chromosomal DNA has more large size than the free DNA molecule: diameter – 11.4–39.7 nm and height – 0.47–1.9 nm. Newfound Ab- DNA complexes are highly stable: hydrolysis of phosphodiester bonds of DNA molecule did not results in Ab release. This indicates that investigated Ab has nonprocessive action’s mechanism.

Conclusion: Our study demonstrates the presence of hydrolytical activity against dsDNA in Ab isolated from serum of patients with autoimmune thyroiditis and highlights an affective role of Ab to dsDNA in pathogenesis of Hashimoto’s thyroiditis.