Peritubular capillary C4d deposition in chronic allograft dysfunction

Peritubular capillary (PTC) C4d staining represents a marker for acute humoral rejection, however, the impact of positive staining on chronic allograft dysfunction has received little attention. Ninety-three renal allograft biopsies from 93 patients were selected from a total of 174 renal allograft biopsies, which were obtained 6 months or more after transplantation (median: 89 months). Fresh frozen renal tissue was stained with monoclonal antibody against C4d. Sixteen of 93 biopsies showed C4d staining in PTC. C4d staining was positive in 40% of acute rejection cases (n=15) and 21% of chronic rejection cases (n=24). When the samples were divided according to C4d positivity, the C4d (+) group had a higher proportion of acute rejection than the C4d (-) group. However, no significant difference was observed between the two groups in terms of the prevalence of chronic rejection. Degrees of histological injury including tubulitis, interstitial inflammation and interstitial fibrosis were not significantly different between C4d (+) and C4d (-) groups. However, the 2-year graft survival rate after biopsy was lower in the C4d (+) group than in the C4d (-) group (24.8% versus 59.0%, p=0.1255). C4d staining in PTC is associated with late acute rejection, but not with chronic rejection based on conventional morphologic criteria in patients with chronic allograft dysfunction.