The DNA-hydrolyzing activity of IgG antibodies from human placenta

Objective: Since during pregnancy and lactation women tend to develop autoimmune processes, characterization of placenta immunoglobulins and their possible catalytic functions is a very important step towards understanding the function of placenta. Methods: ELISA, affinity chromatography, SDS-PAGE and MALDI mass spectrometry were used. Results: It was shown, that ten placentas contain in average 1.1 +/- 0.33 mg IgGs/g of placenta and 0.11 +/- 0.1 mE anti-DNA antibodies/g of placenta. All ten individual IgG preparations were characterized by a specific ratio and various combinations of heavy (47.5-51.7 kDa) and light (22.2-33.3 kDa) chains with different molecular masses. All intact IgGs demonstrate DNase but have not amylase activity. Several strict criteria have been used to show that the DNase activity is an intrinsic property of placenta IgGs. The heavy chains of antibodies were catalytically inactive. The light chains of 22-24 kDa of all IgGs demonstrated maximal DNase activity, while the chains of approximately 25-33.2 kDa were significantly less active. IgGs were completely inactive after dialysis against EDTA. The optimal external cofactors of placenta DNase abzymes are Mg2+ and Cu2+ ions, while, activity in the presence of Mn2+ and Ca2+ is approximately 3-4-fold lower. Activation of DNase abzymes by Cu2+ ions was revealed for the first time. Placental antibodies possess selective cytotoxicity against cancer cells. Conclusion: It was shown previously, that appearance of serum DNase abzymes is the good indicator of the beginning and obvious spontaneous or induced autoimmune diseases. The detection of placenta DNase antibodies indicates that during pregnancy, autoimmune processes can affect this organ.