Nephritogenic antibodies bind in glomeruli through interaction with exposed chromatin fragments and not with renal cross-reactive antigens

Abstract

Cross-reactivity of anti-double stranded DNA (anti-dsDNA) antibodies with glomerular antigens has been postulated as a key factor in the development of lupus nephritis. Because no direct proof has been presented on anti-dsDNA antibodies binding in vivo to glomerular structures, we have analysed the binding of potentially nephritogenic anti-dsDNA antibodies to α-actinin and laminin. By enzyme-linked immunosorbent assay and surface plasmon resonance (SPR) analyses, we demonstrate that monoclonal antibodies (mAbs) bind both double-stranded DNA and α-actinin at high affinity. However, when added to nephritic kidney sections they did not bind to such structures, but rather to nucleosome-containing structures within the mesangial matrix or the glomerular basement membranes (GBMs). Nucleosomes, anti-nuclear antibodies and complexes of them were tested for their binding to glomerular components such as agrin, perlecan and laminin using SPR analysis. Nucleosomes bound to laminin, marginally to agrin, but not to perlecan or heparan sulphate-depleted agrin. Anti-histone H2B and anti-nucleosome antibodies in complex with nucleosomes slightly increased the binding of nucleosomes to agrin, while binding to laminin was slightly decreased compared to nucleosomes alone. In conclusion, the availability of nucleosomal antigens and the binding of these antigens to components of the mesangial matrix and GBM seem crucial for the glomerular deposition of immune complexes.

Autoantibodies in systemic autoimmune diseases: specificity and pathogenicity

“…An example of such cross-reactivity is antidsDNA antibodies in SLE, which have been shown to recognize antigens in the glomerular basement membrane, where these autoantibodies can deposit (44)(45)(46)(47). While the binding of some anti-dsDNA antibodies to glomeruli depends on the presence of nucleosomes containing DNA on the glomerular membrane, the contribution of cross-reactivity to renal pathology has also been demonstrated (48,49).…”

Glomerular Autoimmune Multicomponents of Human Lupus Nephritis In Vivo

“…12,[16][17][18][19][20] Chromatin and nucleosomes deriving from ineffective fragmentation may interact with negatively charged constituents of the basement membrane 7,16 and become the planted antigen for anti-dsDNA (and autoantibodies of other specificities). 6,7,9,16 Other potentially nephritogenic antibodies different from anti-dsDNA have been proposed 10,11,[21][22][23][24][25][26] ; overall, it has been estimated that anti-DNA deposition in LN accounts for not more than 10%-20% of eluted IgG overall, 27 implying that IgG not recognizing DNA represents the vast majority of antibodies in glomeruli. Renal targets of autoimmunity in human LN are, however, unknown.…”

“…[6][7][8][9][10][11][12] They consider a pre-eminent role of circulating anti-double stranded DNA (dsDNA) antibodies that they can interact, for mimicry, with glomerular antigens expressed at the cell surface of podocytes and mesangial cells 7,[13][14][15] or in the glomerular basement membrane. 12,[16][17][18][19][20] Chromatin and nucleosomes deriving from ineffective fragmentation may interact with negatively charged constituents of the basement membrane 7,16 and become the planted antigen for anti-dsDNA (and autoantibodies of other specificities).…”

Glomerular Autoimmune Multicomponents of Human Lupus Nephritis In Vivo (2)

“…6 Three categories of autoantibodies have been identified that constitute the basis for any pathologic and clinical consideration. The first category targets implanted antigens (DNA, histones, and nucleosomes), [7][8][9][10] mainly deriving from breakdown of apopotic cells. The second category of antibodies binds C1q, which is a component of the complement cascade accumulating in the kidney in LN.…”