Lupus autoantibodies interact directly with distinct glomerular and vascular cell surface antigens

Abstract

We have identified monoclonal anti-DNA antibodies derived from lupus prone MRL-lpr/lpr mice that produce glomerular immune deposits and nephritis after passive transfer to normal mice. Particularly noteworthy is that the location of immune deposition varied among nephritogenic Ig, and this was associated with distinctive histologies and clinical disease profiles. Although their autoantigen binding properties differed, they were highly cross-reactive, in a manner similar to Ig deposited in glomeruli of lupus mice. This antigen binding profile was also typical of other previously described nephritogenic autoantibodies that bound directly to glomerular antigens to initiate immune deposit formation. In this study, we questioned whether ligation of different glomerular antigens by individual autoantibodies could contribute to the observed differences in the location of immune deposits. To examine this possibility, monoclonal anti-DNA antibodies (IgG2a) that produced glomerular immune deposits in different locations were evaluated. H221 produced mesangial, intracapillary (that is, intraluminal or within the capillary lumen) and subendothelial deposits associated with heavy proteinuria, whereas H147 produced mesangial, subendothelial and linear basement membrane deposits associated with proliferative glomerulonephritis. Initially, the capacity of H221 and H147 to bind directly to glomerular and vascular cell surfaces was evaluated. As demonstrated by FACS, H221 bound preferentially to mesangial cells whereas H147 bound preferentially to endothelial cells. To identify possible target cell surface antigens, Western blots, immunoprecipitation of surface labeled cells, and 2D gel electrophoresis were employed. H221 reacted with a 108 kDa protein on mesangial cells not identified by H147, whereas H147 reacted with a 45 kDa protein on endothelial cells not identified by H221. These results support the hypothesis that some nephritogenic lupus autoantibodies initiate immune deposit formation through direct interaction with glomerular antigens. Furthermore, they suggest that the site of immune deposition is determined by both antigen binding properties of the relevant antibody and the location of its target ligand within the glomerulus. In a given individual, therefore, the predominant autoantibody-glomerular antigen interaction may influence the morphologic and clinical phenotype expressed. Variation in the predominant interaction may also contribute to variations in disease expression among individuals with lupus nephritis.

Glomerular Autoimmune Multicomponents of Human Lupus Nephritis In Vivo

“…12 The prototype produced by clone H147 (an IgG2 encoded by 7183/81X VH gene) 33 induces the formation of glomerular or tubular basement membrane, mesangial immune deposits, and proliferative GN after passive transfer to normal mice. 12 The target antigen of these antibodies was recognized as a protein of 46 kD, which is the same molecular mass of a-enolase in the work by D'Andrea and colleagues, 12 but it has not been characterized until now. We attempted to fill this gap by characterizing the target protein of the mouse IgG2 above (a gift from M.M.)…”

“…[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).…”

“…[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). 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.…”

Critical comparative analyses of anti–α‐actinin and glomerulus‐bound antibodies in human and murine lupus nephritis

“…molecules (8)(9)(10)(11). Irrespective of which parameters are important, the release (and trapping in the glomerulus) of relevant antigens recognized by nephritogenic antidsDNA antibodies must be a crucial event for making target molecules available for the antibodies (5,12) if the central antigens are not naturally available as, for example, in glomerular basement membrane (GBM) structures.…”

“…Contemporarily, studies of the nephritogenicity of anti-dsDNA antibodies follow 2 main directions, based on the following theories: either anti-dsDNA antibodies form complexes with nucleosomes that deposit in glomeruli (13)(14)(15)(16), or anti-dsDNA antibodies cross-react with non-nucleosomal glomerular structures (8,9). Recently, antibodies to ␣-actinin, a major structural component of glomerular podocytes and mesangial cells (17,18), have attracted particular attention, because ␣-actinin may represent a target molecule for nephritogenic anti-dsDNA antibodies (10,11,19,20).…”