Number of interstitial capillary cross-sections assessed by monoclonal antibodies: relation to interstitial damage

Using thin Plexiglass sections stained with silver, the peritubular capillary area and number of capillary cross-sections can predict both interstitial damage and plasma creatinine concentrations. This technique is both difficult to perform and time-consuming. We have restudied this topic using conventional cryostat sections from 46 biopsies with chronic glomerulonephritis and tubulointerstitial nephritis and two monoclonal antibodies (MoAb) recognising capillary endothelium. Seven pretransplant biopsies acted as controls. The number of capillary cross-sections/mm2 was counted, and the degree of tubular atrophy, interstitial fibrosis and cell infiltration of the interstitium independently assessed on a semiquantitative scale using paraffin sections. These results were correlated with the plasma creatinine or 51Cr-EDTA glomerular filtration rate. Mean number of capillary cross-sections in normal interstitium was 373 +/- 50/mm2, and in the 46 biopsies studied 242 +/- 57/mm2. The number of capillary cross-sections reflected the plasma creatinine (r = 0.82, P less than or equal to 0.0001) and the glomerular filtration rate (r = 0.64, P less than or equal to 0.0001) at the time of biopsy with greater accuracy than any of the conventional gradings of interstitial damage on paraffin sections. We conclude that the use of anti-endothelial cell monoclonal antibodies makes counting capillary cross-sections easy and reliable, and that this technique can be employed to assess the extent of interstitial damage in conventional cryostat sections.