1. Adult female Wistar rats underwent uninephrectomy (n = 8) through a flank incision, or a sham operation (n = 7). One to two weeks later the kidney was perfused in situ and glomeruli were isolated from cortical tissue by sequential sieving, and partially digested. Glomerular leucocytes were labelled with a mouse monoclonal antibody against leucocyte common antigen followed by a fluorescein-labelled anti-mouse immunoglobulin to allow counting.
2. In a further group of animals 24 h albumin excretion and glomerular size were measured 2 weeks after either uninephrectomy (n = 6) or sham operation (n = 6).
3. Glomerular leucocyte number was significantly increased in uninephrectomized animals (15.7 ± 0.9 versus 8.9 ± 0.4, P <0.001), with some glomeruli having leucocyte numbers comparable with those seen in glomerulonephritis.
4. Albuminuria was not increased 2 weeks after uninephrectomy (233 ± 35 versus 170 ± 42 μg/24 h, not significant), and glomerular size was unchanged. Light microscopical appearance was normal.
5. An increase in glomerular leucocyte number is an early response in what was previously considered a non-immunological lesion. It precedes the development of renal scarring and may be important in the pathogenesis of this process.