Single Center Experience of C4d Staining of Kidney Transplant Biopsies

R. Prashar, L. Yessayan, M. Goggins, V. Karthikeyan, K. Venkat, A. Patel.

Division of Nephrology and Transplant Institute, Henry Ford Hospital, Detroit, MI.

Meeting: 2015 American Transplant Congress

Abstract number: D61

Keywords: Biopsy, Graft survival, Kidney transplantation, Rejection

Introduction: While a diffuse positivity (>50%) of C4d in kidney transplant peritubular capillaries strongly co-relates with the presence of acute or chronic antibody mediated rejection, definitive data on the significance of focal (10-50%) C4d deposits on graft outcomes are still lacking. We present a single center experience of C4d staining in kidney transplant biopsies.

Methods: All consecutive indication-driven (increase in serum creatinine +/- proteinuria) biopsies in primary kidney transplant recipients done at our institution between December 2011 and March 2013 were retrospectively reviewed. C4d positivity was assessed by immunohistochemistry along with conventional histopathological examination. Biopsies were classified as C4d negative (<10%), with focal (10%-50%) or with diffuse (>50%) C4d deposits. Antibody Mediated Rejection (AMR) and Cell Mediated Rejection (CMR) were diagnosed using Banff 2007 criteria.

Results: Patient characteristics are summarized in Table 1.

Characteristic	Value
Mean Age (y)	53 +/- 15.4
Sex	65% Male
Race	66% African Americans
Mean cPRA (%)	16.9 +/- 28.3
Donor type	73% Deceased Donors
Mean time after transplantation to biopsy (d)	747 +/- 1093

Patients were followed for a mean of 646 +/- 273 days. Out of the 100 kidney transplant biopsies done during the 16-month period, 58% were C4d negative, 33% were focal C4d positive and 9% were diffuse C4d positive. While 6/9 (66%) patients with diffuse C4d positivity had AMR, no patients with no or focal C4d positivity were found to have AMR. CMR was diagnosed in 5/9 (55%) patients with diffuse C4d positivity, and the incidence of CMR was 24% and 29% in focal or no C4d positive biopsies respectively (statistically in-significant). While the incidence of graft loss was 55% in diffuse C4d biopsies, there was no statistically significant difference between incidence of graft loss in focal positive (25% graft loss) and C4d negative (31% graft loss) biopsies.

Conclusion: Our data suggest no implication of focal C4d positivity in peritubular capillaries in kidney transplant biopsies in diagnosis of AMR, CMR or incidence of graft loss. We are currently evaluating association of Donor Specific Antibodies with focal C4d positivity in kidney transplant biopsies and its impact on graft survival.

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