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<0.05). Histologically, the C4dPTC-positive group had findings suggestive of acute cellular rejection more commonly than the C4dPTC-negative group (p<0.01).Conclusions
Evidence of humoral rejection, as demonstrated by C4dPTC deposition, was concurrently present in significant portions of post-transplant IgAN biopsy specimens and was associated with more rapid deterioration of renal function. These results suggest that C4dPTC positivity needs to be determined at the time of biopsy even in cases of post-transplant glomerulonephritis and immunosuppression may need to be modified accordingly.