Proliferating cell nuclear antigen (PCNA) as a diagnostic marker of acute cellular rejection in routinely processed biopsies of renal allografts

Abstract

Seventy-eight renal allograft biopsies taken for the management of graft dysfunction were analysed retrospectively by labelling with antibodies to proliferating cell nuclear antigen (PCNA) to assess whether this marker could distinguish episodes of rejection. Routinely processed, paraffin-embedded biopsies with focal or diffuse cellular infiltrates were selected and the percentage of infiltrating cells in the cortical interstitium which stained with PCNA antibody were counted (PCNA index). The area of cellular infiltration was also estimated by a morphometric point-counting technique. The biopsies were divided into two groups based on standard clinical criteria; those with acute rejection (n = 31) and those with other causes of graft dysfunction (n = 47). The PCNA index was significantly higher in episodes of acute rejection (7.9%) compared to non-rejection (2.1%). This was independent of time after transplantation. The PCNA index was also greater in rejecting kidneys containing only focal cellular infiltrates (percentage area of cellular infiltration < 13.1%). Thus PCNA staining may be of use in the differential diagnosis of rejection in routinely processed biopsies of renal allografts where there are only focal inflammatory infiltrates, otherwise not diagnostic of cellular rejection.