Ultrastructural changes of tubular basement membranes in immunologic renal tubular lesions in humans.

Ultrastructural changes in the tubular basement membrane (TBM) of 65 renal biopsy specimens from patients with nephropathies or transplant rejection were examined for their potential relationship to deposits observed along the TBM by immunofluorescence (IF). The TBM showed various alterations: irregularities with thickening, lamellation, duplication, and clear spaces. Granular vesicles or inclusions were present inside the thickened TBM. The morphologic changes of the TBM occurred regardless of the severity of rejection of transplants and the type of deposits observed on IF. Electron-dense deposits inside or along the TBM were not found in cases of linear deposits, however. Although these changes were not strictly specific to tubular immune diseases, they could reflect a reaction of the TBM to immune complexes or deposits of antibodies to TBM with degeneration of tubular epithelial cells and sometimes regeneration of a new TBM.