An acute model for IgA‐mediated glomerular inflammation in rats induced by monoclonal polymeric rat IgA antibodies

SUMMARY An acute model Tor IgA-mediated glomerular inflammation in rats was induced by the in situ deposition of IgA directly into the glomerular mesangium. F(ab')2 anti-Thyl MoAb was used to anchor an antigen. DNP (2,4-dinitrophenol), in the glomeruli of rats. Subsequent infusion of rat polymeric (p-) or monomeric (m-) IgA MoAb with specificity for DNP resulted in mesangial deposition of IgA in both groups of rats. However, acute proteinuria was observed only in p-IgA-treated rats and not in PBS- or m-IgA-treated rats. Immunofluorescence analysis revealed deposition of C3 in an identical pattern to that of IgA in the glomeruli of p-IgA-treated rats. No mesangial deposits of C4 or Clq were seen in these animals. Rats receiving m-IgA or PBS displayed no detectable C3, C4 or Clq deposition. The amount of proteinuria in p-IgA-treated rats was related to the amount of deposited C3. The presence of intraglomerular monocytes was only observed 2 days after p-IgA injection. By light microscopy, aneurysm formation, mesangial hypercellularity and matrix expansion were seen only in p-IgA-treated rats. However, by 37 days post-injection complete resolution of the lesions was observed. No histological renal changes were observed in PBS- or m-IgA-trcatcd rats. In conclusion, an acute form of IgA-mediated nephritis in rats was induced by p-lgA but not by m-IgA. This reproducible model provides a basis for further study into the mechanisms of IgA-mediated glomerular inflammation.