Surface charge distribution is a determinant of antigen deposition in the renal glomerulus: studies employing ‘charge-hybrid’ molecules

Abstract

SUMMARYThe deposition of antigens and immune eomplexes (IC) in the renal glomerulus is charge-dependcnl. The demonstration that molecules of nei anionic charge, but with discrete positively charged regions, exhibit affinity for the glomerular basement membrane (GBM) extends this concept. Charge hybrid (polar) molecules were constructed by covalently coupling small polycations (lysozyme or linear poly-L-lysine chains with a mean of 17 and 20 residues) to larger polyanions (ovalbumin or human scrum albumin (HSA)). Although the products were of overall net anionic charge they still bound to glomerular structures. ImmunoHuorcscence studies performed after I.v. injection ofthe samples into rats revealed that HSA;poiy-L-Iysine had the highest atfinity. Radioisotopic measurements showed uptake of HSA: poly-L-lysine to be a function of the number of lysine residues; binding of HSA: poly-L-lysine:u was 2-5 times higher than HSA:po!y-L-Iysinen iP<OOi). Prior injection of a small competing polycation (polyethyleneimine 1200) reduced uptake of HSA.poly-L-lysine by 75%, indicating the charge-based nature of the interaction. HSA:poly-L-iysine<i, alone was effectively eliminated from the gli>meruli within 12 h. Administration of HSA :poiy-L-lysine followed by anti-HSA antibody induced immune complex formation in the capillary wall, giving rise to a granular immunofluorescence pattern and discrete subendotheliai and subepithelia! deposits. Molecules with polar structure do occur naturally and may contribute to immune eomplex formation in glomerulonephritis.

Glomerular injury induced by cationic 70-kD staphylococcal protein; specific immune response is not involved in early phase in rats

“…These aggregates should be able to bind to the glomerular capillary wall, as it is known that possession of discrete positively charged regions in molecular complexes of net anionic charge can endow them with affinity for the GBM. 30 This latter binding mechanism requires more time than direct in situ formation, which would allow material to reach the nonperfused kidney. In fact, p70 could only be detected at 15 min in the perfused kidney, after which both kidneys were negative for this antigen.…”

CD4+ T Cells Recognizing Specific Antigen Deposited in Glomeruli Cause Glomerulonephritis-like Kidney Injury

“…The endothelial cell fenestration in renal glomeruli favors the entrapment of complexes of a molecular size of about 200 kDa (35,43). To verify this prediction, we injected pooled fractions of three size ranges (600 -300, 300 -150, and Ͻ150 kDa) of OVA polymers prepared with a FPLC superose 6 column (as described under Materials and Methods) iv into SCID mouse tail veins.…”

“…Based on investigations of Vogt and Batsford (34,35) and modifying a chemical crosslink protocol (36), we developed a procedure to synthesize and purify an OVA polymer of a defined size and charge. Briefly, we prepared OVA (10 mg/ml) in 0.1 M Na 2 HPO 4 buffer (pH 7.5), filtered it through 0.22 m, and added 4 l/ml of a 50% glutaraldehyde solution (photographic grade, Sigma).…”

Influence of Isoelectric Point on Glomerular Deposition of Antibodies and Immune Complexes

“…24.4% of the deposited ICs had gained access to the GBM, although it lay in the pi range pH 4.0-8.2. A possible explanation for this phenomenon might be the formation of charge hybrid molecules [12], In the latter case it is conceivable that the overall net charge is anionic, but that there are some cationic regions exposed which confer affinity for the GBM [ GBM electrostatically and that the affinity of both in creases with pi to a certain degree [9,19]. According to size exclusion chromatography the estimated mean size of the injected ICs was about 430 kD, indicating a probable structure of two Agand two Ab molecules (AbiAg2) per IC unit.…”