Aim: To characterise clinically the patients with C4d in peritubular capillaries deposits (C4dPTCD) and/or circulating anti-HLA class I/II alloantibodies. To determine the correlation between positive C4dPTCD and
circulating anti-HLA class I/II alloantibodies during episodes of graft dysfunction.
Subjects and Methods: C4d staining was performed in biopsies with available frozen tissue obtained between January 2004 and December 2006. The study was prospective from March 2005, when a serum sample
was obtained at the time of biopsy to detect circulating anti-HLA class I/II alloantibodies.
Results: We studied 109 biopsies in 86 cadaver renal transplant patients. Sixteen of these (14.7%) presented diffuse positive C4dPTCD. There was a 13.5% rate of +C4dPTCD incidence within the first six months of
transplantation and 16% after six months (p>0.05). Half of the +C4dPTCD in the first six months was associated with acute humoral rejection. After six months, the majority of +C4dPTCD (n=7/8) was present in biopsies
with evidence of interstitial fibrosis/tubular atrophy and/or transplant glomerulopathy. The C4dPTCD was more frequent in patients with positive anti-HCV antibodies(p<0.0001), a previous renal transplant (p=0.007), and with a panel reactivity antibody (PRA) ≥ 50%(p=0.0098). The anti-HCV+ patients had longer time on dialysis (p=0.0019) and higher PRA(p=0.005). Circulating anti-HLA I/II alloantibodies were screened in 46 serum samples. They were positive in 10.9% of samples, all obtained after six months post transplant. Circulating
alloantibodies were absent in 92.5% of the C4d negative biopsies.
Conclusion: We found an association between the presence of C4dPTCD and 2nd transplant recipients,higher PRA and the presence of anti-HCV antibodies.
The presence of HCV antibodies is not a risk factor for C4dPTCD per se, but appears to reflect longer time on dialysis and presensitisation. In renal dysfunction
a negative alloantibody screening is associated with a reduced risk of C4dPTCD (<10%)
