IMMUNE-COMPLEX DEPOSITION IN BOWMANS CAPSULE IS ASSOCIATED WITH PARIETAL PODOCYTES

We have recently documented the presence of podocytes lining part of B owman's capsule at the vascular pole, in adult human kidney. In this s tudy, we describe the deposition of immune complexes in Bowman's capsu le in association with these parietal podocytes, We examined 1 year's consecutive human renal biopsies (n=170). Transmission electron micros copy (TEM) revealed 18 cases in which parietal podocytes were present. Of these 18, there were 11 cases of glomerulonephritis, in which immu ne complexes were demonstrated in the capillary tuft by both TEM and d irect immunofluorescence microscopy. In seven of these 11 cases, TEM s howed immune complex-type deposits in Bowman's capsule, always associa ted with parietal podocytes. These deposits were similar in size, appe arance, and distribution to the deposits in the capillary tuft. By con trast, non-specific electron densities within Bowman's capsule were fo und beneath both squamous parietal cells and parietal podocytes. In fo ur cases, Bowman's capsule also showed focal positive immunostaining f or complement components and/or fibrinogen. Both parietal and visceral podocytes showed similar fusion of pedicels. We suggest that filtrati on through parietal podocytes may be responsible for immune complex de position and subsequent damage to the vascular pole of the glomerulus in human renal disease.