Role of C4d in the Diagnosis and Prognosis of Native Renal Diseases

INTRODUCTION: C4d is a biomarker of the complement cascade and has a primary role in the diagnosis of antibody-mediated rejection in solid organ transplantation. The present study was undertaken to investigate the role of C4d in the diagnosis and prognosis of native renal diseases. METHODS: An observational cross-sectional study was conducted in the Department of Pathology from September 2017 to September 2019. In this study, we applied C4d staining by immunohistochemistry in 51 native renal biopsies. Semiquantitative scoring was done on the basis of intensity of C4d staining along the glomerular capillary wall (0–3) and mesangium (0–3), tubules (0–3), and arteries (0–3). These individual scores were added to get the total C4d score (0–12) which was correlated with chronicity index, serum urea and creatinine levels. Glomerular C4d score was correlated with 24 h urinary protein as well as with immunofluorescence deposition of immunoglobulins and complements. RESULTS: We found a linear positive correlation (P < 0.05) between the total C4d score and serum creatinine; tubular C4d score and serum creatinine; and glomerular C4d score along capillary wall and 24 h urinary protein. A positive correlation (P < 0.05) was found between glomerular C4d score along the capillary wall with immunofluorescence deposits of immunoglobulins and complements, suggesting the efficacy of C4d as a surrogate marker in the diagnosis of native renal diseases. CONCLUSIONS: C4d deposition is associated with a poor prognosis in renal diseases and an accelerated deterioration of renal function. It also plays a role as a surrogate marker in diagnosis of native renal diseases.