Immunofluorescent studies of urinary casts.

Immunofluorescent staining of urinary casts of patients with chronic glomerulonephritis or with acute renal failure was performed. Urinary and cast Tamm-Horsfall mucoproteins were purified by a modified McQueen's method. Rabbits were immunized by both of these materials to obtain antisera. The antigenic specificity of the prepared material was examined by Ouchterlony gel diffusion method and immunoelectrophoresis. Indirect and direct immunofluorescent staining methods were done using Tamm-Horsfall mucoprotein antiserum and FITC-GARG, FITC-labelled IgG, IgA, IgM, C3 and albumin. Hyaline casts of both chronic glomerulonephritis and acute renal failure demonstrated fluorescence with Tamm-Horsfall mucoprotein antiserum. The nature of the granular casts of chronic glomerulonephritis seemed to be different from those of acute renal failure because the granules of the former fluoresced for some serum protein fractions, but the latter fluoresced only for Tamm-Horsfall mucoprotein. The absence of fluorescence with epithelial casts for any serum protein fractions implied a different pathogenesis for epithelial casts as compared to granular casts, contrary to Lippman's assumption. A routine technique of immunofluorescent staining of urinary casts was developed. The interpretation of urinary casts should be more specific by this new technique.