Penetration Of IgG 3 Subtype Of Anti-dsDNA Antibodies Into Living Human Renal Mesangial Cells: New Mechanism For Renal Pathogenicity Of Anti-DNA Antibodies

Objective To study whether the IgG3 anti-dsDNA antibodies are able to penetrate into living hunman renal mesangial cells(HRMCs) or not,and set up a model regarding the penetration of IgG anti-dsDNA antibodies into renal cells in vitro, and to explore whether the penetration of IgG anti-dsDNA antibodies into living cells may play an important role in the pathogenesis of lupus nephritis (LN), and to validate the hypothesis of the IgG anti-dsDNA antibodies can penetrate into renal cells selectively and finally induce LN.Methods Mouse monoclonal IgG3 anti-dsDNA antibodies were labeled by fluorescein isothiocyannate(FITC), and the HRMCs were cultured in vitro. FITC labeled IgG3 anti-dsDNA antibodies were added into the HRMCs, then incubated for 45 min at 37℃, the fluorescence intensity was detected by fluorescence microscope, so as to analyse whether the IgG3 anti-dsDNA antibodies are able to penetrate into living HRMCs or not. Moreover, HRMCs were subdivided into 1, 15, 30 and 45 min groups, incubated with FITC labeled IgG3 anti-dsDNA antibodies, then the process of IgG3 anti-dsDNA antibodies penetrating into HRMCs and its fluorescence intensity were observed by laser confocal microscopy. All the data were analyzed by SPSS10.0.Results The IgG3 anti-dsDNA antibodies can penetrate into the living cells, localize in the cytoplasm, and continue to deposit in the nucleus; there was a significant difference between all groups (P<0.001), and the differences between arbitrary two groups all had statistical significance(P<0.001), and there was a correlation between fluorescence intensity and incubation time (rs = 0.967, P <0.001). The combination of IgG3 anti-dsDNA antibodies with nucleus could be observed when the incubation time near 45 minutes.Conclusions The IgG3 anti-dsDNA antibodies have the ability of penetration into living cells, and may have the ability of nuclear localization or even localize within nuclear. The amount of IgG3 anti-dsDNA antibodies entering the cells increased with the incubation time, and this event may be influenced by many factors. The IgG anti-dsDNA antibodies of SLE patients may probably through the penetration of antibodies into renal cells selectively and cause the damage of kidney tissue.