Detecção de complemento - C4d em capilares peritubulares e análise morfológica de biópsias de enxerto renal

Abstract

C4d is the degradation product of the activated complement factor C4, a component of the classical complement cascade which is covalently bound to the tissue at the interface between endothelium and basement membrane. C4d deposition in peritubular capillaries has been described as a marker of humoral renal graft rejection. The objectives of this study were to characterize the epidemiological and clinical features of kidney transplant patients of the Nephropathology Department of the University of Triangulo Mineiro, and to analyze morphologically and by immunohistochemistry for C4d their biopsies to classify it according to Banff 07.To analyze the fibrosis the fragments were stained with Picro-sírius. The slides were viewed under polarized light with the 40x objective and calculate the percentage of fibrosis per area of the examined field (% F) using KS300 and ImageJ programs. For peritubular C4d detection was used the technique of immunohistochemistry with primary antibody anti-C4d. For detection of IgA, IgG, IgM, C3 and C1q was used direct immunofluorescence technique. The slides were viewed by fluorescence microscope and analyzed according to their positivity and site of deposit. The diagnoses were made according to the presence of C4d (C4d0, C4d1, C4d2 and C4d3) and classified according to Banff 07. The mean age was 41.1 years and had positive correlation with the percentage of fibroses (r = 0,452, p = 0005). The median of the percentage of fibrosis was 1% in the group C4d0, 1% in C4d1, 2% in C4d2, and 3% in C4d3 (H = 3.4, p = 0.32) and the correlation between the intensity of fibrosis and deposition of C4d was positive (r = 0,264, p = 0113). Between the diagnosis, rejection mediated by antibodies (RMA) represented 36.7%, rejection mediated by cells (RMC) 16.7%, borderline lesions (BL) 25% and interstitial fibrosis/tubular atrophy (TF/TA) 18,3%. Comparing according to the type of diagnosis, the mean fibrosis for ARMA was 2%, ARMC 1%, CRMA 5%, BL 2.5%, TF/TA 4% and others 1% (H = 6.484, p = 0.166). There was positivitity for IgA, IgM and C3 in groups C4d0, 1, 2 and 3, for IgG and fibrinogen in groups C4d2 and 3, and for C1q in groups C4d1, 2 and 3. C4d3 group showed a higher percentage of fibrosis, with elevated serum creatinine levels, and a positive correlation between fibrosis and intensity of C4d expression. C4d is an important marker of humoral renal graft rejection and essential to determine the diagnosis, however, it has some limitations. The co-expression of C4d with IgG and C3 could indicate the activation of the classical complement pathway. The relation between C4d, fibrosis and creatinine levels may be indicative of renal function decline and worse prognosis.