Analysis of the renal pathogenicity of nephritogenic antibodies in SLE
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IgG anti-double stranded DNA antibodies associated with systemic lupus erythematosus are thought to be pathogenic to the kidney by cross reacting, directly or indirectly, with glomerular antigens, leading subsequently to immune complex formation in situ and complement activation. To determine if lupus anti-DNA antibodies may also contribute to renal damage by directly influencing gene expression in kidney residential cells, genome-wide gene expression profiling was performed in glomerular mesangial cells derived from the MRL-lpr/lpr lupus prone mouse treated with nephritogenic anti-DNA antibodies.;Antibodies were first characterized by their binding to isolated glomeruli and mesangial cells. The nephritogenic monoclonal antibody R4A was found to be able to penetrate into live mesangial cells without affecting the cell viability. In the microarray study, nephritogenic, but not non-nephritogenic antibodies, significantly induced a number of transcripts, including several chemokines, iNOS, Lipocalin2, and members of NFkappaB pathway. The expression of these genes was confirmed by real-time PCR and methods to detect the relevant proteins. Blocking Fcgamma receptors or using Fc signaling gamma chain knockout mesangial cells had no impact on the gene regulation effect of R4A, indicating a Fc-independent mechanism. Activation of NFkappaB was found in mesangial cells treated with pathogenic antibody. Further evidence for antibody-induced renal gene expression was provided by the up-regulation of these genes in the glomeruli of SCID mice injected with the pathogenic antibody, and by the observation that marker gene expression in glomeruli increased over time in lupus prone mice with the development of glomerular antibody deposition and active nephritis. Furthermore, a gene expression pattern with stronger chemokine response was observed in pathogenic antibody stimulated MRL/lpr mesangial cells, in contrast to those from normal BALB/c background which had weaker inflammatory response but more transcription factors and signal transduction molecules induced by the antibody.;We conclude that the renal pathogenicity of anti-DNA antibodies may be also attributed to their capability of directly modulating gene expression in kidney mesangial cells. Finally, we propose that direct modulation of kidney cell gene expression by nephritogenic antibodies may be involved not only in the pathogenesis of lupus nephritis, but can also contribute to other autoantibody-mediated glomerular diseases.
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