Immunofluorescent Deposits on the Tubular Basement Membrane in Human Renal Transplant

In this retrospective study, the presence of tubular basement membrane (TBM) deposits of IgG and/or C3 was demonstrated in 41 renal transplants (out of 95 studied). The follow-up of these transplants varied from 9 to 19 years. The deposits were of ‘linear’ type in 9 cases (circulating anti-TBM antibodies were detected in 7 cases by radioimmunoassay tests and/or indirect immunofluorescence), ‘granular’ type in 22 cases and ‘atypical’ with linear and granular segments in 10 cases. Light microscopic diagnosis was acute rejection in 26 cases (33 biopsies) associated with deposits along the TBM: linear (6 cases), granular (13 cases) and atypical (7 cases). Chronic rejection present in 15 transplants (21 biopsies) was associated with linear (2 cases), granular (9 cases) and atypical (4 cases) deposits along the TBM. Electron microscopic study of renal tubules showed altered TBM with thickening, lamellation and splitting. Electron-dense deposits were not demonstrated in cases of linear deposits. A long-term follow-up study did not show any difference in survival of transplants presenting acute or chronic rejection associated or not with TBM deposits. If we consider the outcome of the transplants with TBM deposits, those with granular type seemed to have the poorest prognosis at long term, whatever the type of rejection. In the linear TBM deposits group, all the transplant nephrectomies which occurred (7 out of 9 cases) have been performed within 5 years.