Late renal graft rejection: pathology and prognosis
Rejection has always been one of the most important cause of late renal graft dysfunction. Aim of the study was to analyze the prevalence of different clinico-pathological variants of rejection that cause late graft dysfunction, and evaluate their impact on long-term outcome. Materials and methods. This is a retrospective study that analyzed 294 needle core biopsy specimens from 265 renal transplant recipients with late (48,8 ± 46,1 months after transplantation) allograft dysfunction caused by late acute rejection (LAR, n = 193) or chronic rejection (CR, n = 78) or both (n = 23). C4d staining was performed by immunofluorescence (IF) on frozen sections using a standard protocol. Results. Peritubular capillary C4d deposition was identified in 36% samples with acute rejection and in 62% cases of chronic rejection (including 67% cases of transplant glomerulopathy, and 50% - of isolated chronic vasculopathy). 5-year graft survival for LAR vs CR vs their combination was 47, 13 and 25%, respectively. The outcome of C4d- LAR was (p < 0,01) better than of C4d+ acute rejection: at 60 months, graft survival for diffuse C4d+ vs C4d- was 33% vs 53%, respectively. In cases of chronic rejection C4d+ vs C4d- it was not statistically significant (34% vs 36%). Conclusion. In long-term allograft biopsy C4d positivity is more characteristic for chronic rejection than for acute rejection. Only diffuse C4d staining affects the outcome. C4d-positivity is associated with worse allograft survival in cases of late acute rejection, but not in cases of chronic rejection.