Donor-specific antibodies,glomerulitis,and human leukocyte antigen B eplet mismatch are risk factors for peritubular capillary C4d deposition in renal allografts

Background:The complement system plays an important role in the immune response to transplantation,and the diagnostic significance of peritubular capillary(PTC)C4d deposition(C4d+)in grafts is controversial.The study aimed to fully investigate the risk factors for PTC C4d+and analyze its significance in biopsy pathology of kidney transplantation.Methods:This retrospective study included 124 cases of kidney transplant with graft biopsy and donor-specific antibody(DSA)testing from January 2017 to December 2019 in a single center.The effects of recipient pathological indicators,eplet mismatch(MM),and DSAs on PTC C4d+were examined using univariate and multivariate logistic regression analyses.Results:In total,35/124(28%)were PTC C4d+,including 21 with antibody-mediated rejection(AMR),eight with renal tubular injury,three with T cell-mediated rejection,one with glomerular disease,and two others.Univariate analysis revealed that DSAs(P<0.001),glomerulitis(P<0.001),peritubular capillaritis(P<0.001),and human leukocyte antigen(HLA)B eplet MM(P=0.010)were the influencing factors of PTC C4d+.According to multivariate analysis,DSAs(odds ratio[OR]:9.608,95%confidence interval[CI]:2.742–33.668,P<0.001),glomerulitis(OR:3.581,95%CI:1.246–10.289,P=0.018),and HLA B eplet MM(OR:1.166,95%CI:1.005–1.353,P=0.042)were the independent risk factors for PTC C4d+.In receiver operating characteristic curve analysis,the area under the curve was increased to 0.831 for predicting PTC C4d+when considering glomerulitis,DSAs,and HLA B eplet MM.The proportions of HLA I DSAs and PTC C4d+in active antibody-mediated rejection were 12/17 and 15/17,respectively;the proportions of HLA class II DSAs and PTC C4d+in chronic AMR were 8/12 and 7/12,respectively.Furthermore,the higher the PTC C4d+score was,the more serious the urinary occult blood and proteinuria of recipients at the time of biopsy.Conclusions:PTC C4d+was mainly observed in AMR cases.DSAs,glomerulitis,and HLA B eplet MM are the independent risk factors for PTC C4d+.