Interstitial capillary in normal and in transplanted kidneys: an ultrastructural study

Knowledge about the normal structure and pathology of interstitial capillary is limited. Splitting and multilayering of the basal membrane (BM), as a marker of chronic rejection, has been published in association with transplant glomerulopathy. The authors investigated the ultrastructural features of the interstitial capillary basal membrane in normal (15 biopsies) and in transplanted kidneys (27 biopsies from 21 patients), expressing transplant glomerulopathy (8 biopsies from 6 patients), acute tubulo-interstitial rejection (9 biopsies from 6 patients), and recurrent or de novo glomerulonephritis (10 biopsies from 8 patients). All biopsies were fixed in 1% OsO4, embedded in Epon, and examined by electron microscope. Measurements of the interstitial capillary BM were made. The BM of interstitial capillary of intact kidney was a homogenous continuous structure, 88 nm in width on average. Thickening with diffuse multilayering of BM was most intensive in patients with transplant glomerulopathy, and much less intensive in patients with acute tubulointerstitial rejection and in patients with recurrent or de novo glomerulonephritis. These findings may provide the first information about the morphology of the normal basal lamina of interstitial capillary and support the diagnostic value of interstitial capillary changes in chronic rejection.