Abstract
Recently immunologic disorders in patients with diabetic nephropathy have been paid much attention in relation to the pathogenesis and progression of diabetic glomerular injury. In order to check the injury of glomerular basement membrane (GBM) in patients with diabetes mellitus (DM), we examined serum anti-GBM antibodies and urinary excretion of GBM antigen in 38 patients with DM (9 cases without proteinuria-non renal DM and 29 cases with proteinuria-renal DM). Trypsin digested ultrasupernatant of human GBM obtained from autopsied kidneys without renal diseases was used as a soluble GBM antigen. Serum anti-GBM antibodies were measured by passive hemagglutination (PHA) and urinary excretion of GBM antigen by reverse PHA (RPHA). Both of these assay systems are as sensitive as RIA and more convenient than RIA. Serum anti-GBM antibodies were positive in 34.5% of patients with renal DM and negative in all patients with non renal DM. In 53 patients with various primary glomerulonephritis serum anti-GBM antibodies were positive in 7.5%. Urinary GBM antigen was excreted in 87.5% in non renal DM and 60% in renal DM with mild proteinuria. These data suggest that in patients with diabetic nephropathy of glomerular injury GBM antigen is excreted from very early stage and possibly this might be the origin of antigenic stimuli to induce anti-GBM antibodies. Further study is needed to analyze more precisely antigenic components which is excreted into urine and to determine whether anti-GBM antibodies we found in this report really play some role for the glomerular injury.
