INFLUENCE OF ISOELECTRIC POINT ON GLOMERULAR DEPOSITION OF ANTIBODIESAND IMMUNE-COMPLEXES

We determined the critical pI (the lowest required pI) for glomerular deposition of monomeric antibodies (Abs) and soluble immune complexes (ICs). For this purpose renal perfusion studies were performed in rats using: (a) a mixture of radiolabeled, affinity-purified native and ca tionic anti-human serum albumin Abs (anti-HSA Abs, pI range 4- > 9.5), and (b) soluble ICs (HSA-anti-HSA Abs, pI range 4-9.3) prepared with the same Ab mixture. The critical pI for the glomerular deposition of monomeric Abs was more than pH 8.2. 24.4% of the Abs eluted from glome ruli of animals receiving ICs revealed a pI lower than pH 8.2. In conc lusion our data show that the critical pI for the glomerular depositio n of macromolecules is somewhat lower than commonly assumed and that I Cs containing neutral and anionic Abs may bind to the glomerular basem ent membrane in significant amounts.