Anti-glomerular basement membrane antibody-induced inflammation in rat cochlear plexus

Autoimmune inner ear diseases have been recognized recently, but the mechanism of hearing loss is still unclear. This study was aimed to induce immunological inflammation in cochlea to establish a model and to examine an effect of prednisolone on the induction. Lewis rats were immunized with normal rabbit IgG in complete Freund's adjuvant, and then injected intravenously with rabbit anti-rat glomerular basement membrane (GBM) antibody twice (anti-GBM Ab group). The binding of anti-GBM antibody and inflammatory cell infiltration in the cochlear plexus were investigated using immunofluorescence microscopy. Immunofluorescence microscopic examination revealed specific binding of anti-GBM Ab to basement membrane of capillaries in the cochlear plexus. Compared to normal rats injected with saline, larger numbers of infiltrated CD4-positive T cells (p < 0.01) and monocytes/macrophages (p < 0.01) were observed. Furthermore, prednisolone suppressed the infiltration of CD4-positive cells (p < 0.05) and monocytes/macrophages (p < 0.01). These results suggest that an inflammatory reaction was induced by binding of anti-basement membrane antibody to cochlear capillaries in inner ear and that this inflammation in cochlea could be reduced by prednisolone.