Peritubular capillary C4d deposition and renal outcome in post-transplant IgA nephropathy

Backgrounds: Immunological staining of the transplanted kidney for C4d in peritubular capillaries (C4dPTC) has emerged as a useful method to detect antibody-mediated rejection in situ. In this retrospective study, we evaluated the prevalence of C4dPTC deposition in allograft renal biopsies diagnosed of IgA nephropathy (IgAN) and analysed its clinical significance. Method: Sixty-six biopsy specimens of post-transplant IgAN, which were obtained to evaluate azotemia and/or heavy proteinuria, were examined by immunohistochemical staining of the paraffin sections with polyclonal antibody for C4d. Results: C4d was stained positively in peritubular capillaries in 16 (24%) of the 66 cases. The C4dPTC-negative (n=50) and C4dPTC-positive groups (n=16) were not different in recipient gender, age, donor age, type of donor (living vs. cadaveric), interval from transplantation to graft biopsy (41.6± 21.8 vs. 48.3±26.1 months) and post-biopsy follow-up period (60.3±23.3 vs. 56.9±25.4 months). During the follow-up period, 12 of 50 (24%) although the incidence of graft failure was not different by the C4d deposition in peritubular capillaries, intervals from renal biopsy to graft failure tended to be shorter in C4dPTC-positive cases than C4dPTC-negative cases. In Kaplan–Meier analysis, the renal allograft function of the C4dPTC-positive group deteriorated more rapidly than that of the C4dPTC-negative group (p