Monoclonal antibodies to heparan sulfate proteoglycan: Development and application to the study of normal tissue and pathologic human kidney biopsies

Monoclonal antibodies (mAbs) (4F2 and 7E12) were prepared against heparan sulfate proteoglycan (HSPG) isolated from bovine glomeruli. Enzyme linked immunosorbent assays (ELISA) and immunoblotting demonstrated that the mABs reacted with HSPG. Indirect immunofluorescence (IF) showed that the mAbs stained renal basement membranes (BMs) and BMs in other organs of normal bovine and human tissues in patterns typical of HSPG. Immunoinhibition studies, and immunoblotting of heparan lyase digested HSPG, indicated that the mAbs recognize HSPG core protein. In kidney biopsies from patients with acute poststreptococcal GN, intact linear glomerular BM (GBM) staining for HSPG was noted despite markedly widened capillary loops. In membranous and in diffuse proliferative lupus GN, loss of HSPG staining was demonstrated at sites of immunodeposition of IgG or C3, while increased staining for HSPG was noted in areas of newly formed GBM. Extensive loss of HSPG was seen in areas of glomerular sclerosis and necrosis. In biopsies from patients with minimal change glomerulonephritis (GN) and mesangioproliferative lupus GN, a normal linear GBM distribution of HSPG was noted. The findings are discussed in the context of current knowledge regarding the pathogenesis of glomerular injury. MAbs to BM HSPG should prove useful for future immunochemical studies, and for the study of diseases of the basement membrane.