The binding of anti-double-stranded DNA (anti-dsDNA) autoantibodies to the glomerular basement membrane (GBM) in lupus nephritis can be explained by two mechanisms: (1) direct crossreactive binding to intrinsic glomerular antigens; (2) nucleosome-mediated binding to heparan sulfate in the GBM. Kalaaji et al. demonstrated using novel techniques that glomerular in vivo-bound antoantibodies bind to nucleosomes/dsDNA derived from apoptotic cells and not to intrinsic glomerular structures.