COMPLICATIONS Nephropathic C4d Complement Split Product in Diagnosis of Immunological Activity of Chronic Allograft Nephropathy A. Mroz, Z. Lewandowski, T. Cieciura, B. Matlosz, J. Pazik, A. Kwiatkowski, J. Szmidt, and M. Durlik ABSTRACT Introduction. Activation of the humoral branch of the immunological response is currently believed to play an important role in pathogenesis of chronic allograft nephrop- athy. The impact of humoral alloreactivity, indicated by the presence of C4d deposits in peritubular capillaries of a renal allograft, on the development of chronic allograft nephropathy is a significant problem in transplantation. The aim of the study was to assess and correlate C4d expression in patients with chronic allograft nephropathy, with clinical and morphological variables, as well as to assess the impact of a change in immunosup- pression regimen on posttransplant course and renal allograft morphology. Patients and methods. Twenty-six patients with chronic allograft nephropathy underwent biopsies to correlate C4d expression with clinical parameters and morphological findings. In all patients azathioprine was replaced with mycophenolate mofetil with additional CsA dose reduction in 12 patients. After 1 year, 14 protocol biopsies were performed. Results. The frequency of C4d peritubular capillary deposition among patients with chronic allograft nephropathy was 30%. C4d expression appeared later after transplantation, was correlated with chronic allograft glomerulopathy and proteinuria but not other clinical or histological variables. C4d deposits displayed no independent impact on serum creatinine level. Proteinuria was significantly more reduced in the C4d(+) group. Progression of chronic morphological changes was significantly accelerated in the C4d(+) group. Conclusion. C4d peritubular capillary expression did not differentiate patients after immunosuppression enhancement, but it predisposed to progression of chronic morpho- logical findings during 1-year observation. From the Department of Transplant Medicine and Nephrology, Transplantation Institute (A.M., T.C., B.M., J.P., M.D.), Depart- ment of Epidemiology (Z.L.), Department of General and Trans- plant Surgery, Transplantation Institute (A.K.), and Department of General, Vascular and Transplant Surgery (J.S.), Warsaw Medical University, and Department of Pathology (A.M.), Medical Centre for Postgraduate Education, Warsaw, Poland. Address reprint requests to Andrzej Mroz, Transplantation Institute, Department of Transplant Medicine and Nephrology, Warsaw Medical University, ul. Nowogrodzka 59, 02-006 War- saw, Poland. E-mail: andrewcio@poczta.wp.pl © 2006 by Elsevier Inc. All rights reserved. 0041-1345/06/$–see front matter 360 Park Avenue South, New York, NY 10010-1710 doi:10.1016/j.transproceed.2005.11.079 Transplantation Proceedings, 38, 97–100 (2006) 97