Immunological properties of glomerular basement membrane antigens solubilized by elastase digestion

Glomerular basement membrane (GBM) was solubilized by hog pancreas elastase and fractionated on Bio-Gel P-2. The composition and antigenic properties of elastase-solubilized GBM were compared with those of whole GBM. Elastase-solubilized bovine GBM (ES-BoGBM) and whole bovine GBM (BoGBM) showed similar amino acid and carbohydrate compositions, suggesting that neither the glycoprotein nor the collagen component of the GBM was selectively solubilized. Administration of rabbit antibodies against elastase-solubilized rat GBM (ES-RtGBM) and whole rat GBM (RtGBM) to rats showed that these preparations had similar nephritogenic properties although the kidney saturation dose was higher with antibodies to ES-RtGBM, suggesting that rabbits may recognize antigenic sites in ES-RtGBM which are not exposed in RtGBM. Radiolabeled ES-BoGBM or ES-RtGBM could be used in a radioimmunoassay to measure the heterologous immune response and the autoimmune response in rats immunized with BoGBM.