C4d Deposition Is Associated With Chronic Allograft Nephropathy in Rats and Could Be Influenced by Immunosuppressants

Abstract

Aims Deposition of C4d in peritubular capillaries (PTC) has been considered to be a marker of humoral immunity in renal transplant. This study is to investigate C4d deposition in rat renal allografts undergoing CAN and the effects of immunosuppressants on it. Methods Fisher 344 rat renal grafts were orthotopically transplanted into Lewis rats following the procedure of Kamada with our modification. All the recipients were given CsA 10 mg/kg −1 · d −1 × 10 d and then divided into 5 groups (each n = 9); (1) Vehicle: vehicle orally, (2) CsA: 6 mg/kg −1 · d −1, (3) RAPA: 0.8 mg/kg −1 · d −1, (4) FK 506: 0.15 mg/kg −1 · d −1, (5) MMF: 20 mg/ kg −1 · d −1. At 4 weeks, 8 weeks, 12 weeks, the rats were sacrificed, renal allografts were harvested and sera were collected. The deposition of C4d was detected by immunofluorescence and analyzed by Integrated Optical Density (IOD). The pathological changes were accessed according to the Banff 97 criteria. Results C4d deposition in PTC was found in all the allografts at 4 weeks, while there was no obvious manifestations of CAN in all the groups; the differences of Banff Score between all groups were not significant ( P > .05). The values of IOD in RAPA and MMF group were lower than those in other 3 groups ( P = .002, .006). The differences between RAPA and MMF, and between other 3 groups were not significant ( P > .05). The intensity of C4d increased along with the progression of CAN, the heaviest C4d deposits in PTC were found at 12 weeks, and meanwhile the severest CAN was found. Comparing with Vehicle group, CsA and FK 506 had no effect on C4d deposition ( P > .05), however, MMF and RAPA obviously decreased the C4d deposition ( P = .000). The intensity of C4d deposition had a significant correlation with the severity of CAN ( r = 0.894, P = .000). Conclusions Our study suggests that the deposition of C4d in allografts appears earlier than pathological changes of CAN and has a correlation with the progression of CAN. MMF and RAPA can attenuate CAN by inhibiting humoral immunity. In contrast, CsA and FK 506 have no effect on humoral immunity.