ANTIBODIES ELUTED FROM ACUTELY REJECTED RENAL ALLOGRAFTS BIND TO AND ACTIVATE HUMAN ENDOTHELIAL CELLS

ANTIBODIES ELUTED FROM ACUTELY REJECTED RENAL ALLOGRAFTS BIND TO AND ACTIVATE HUMAN ENDOTHELIAL CELLS.
N. LucchiariI¹, C. Xu², N. Panajotopoulos¹, H. Rodrigues¹ , L. E. Ianhez³, J. Kalil^1,4, and D. Glotz². Immunology Laboratory - Heart Institute¹, Renal Transplantation Unit - Urology³, Department of Medicine, Division of Allergy and Clinical Immunology⁴ Faculty of Medicine, University of Sao Paulo, Sao Paulo, Brazil. .²Unitè de Recherche "Immunopathologie Humaine"-INSERM U 430, Hôpital Broussais, Paris-France. ²

This study was designed to investigate the possible involvement of anti-endothelial antibodies (EAbs) in acute irreversible renal graft rejection.Eluates from 25 renal allografts, lost by irreversible rejection (n =22) and by renal vein thrombosis (n=3), used as controls, were tested against a panel of cultured Human Umbilical Vein Endothelial Cells (HUVEC). All patients were under immunosuppression at the time of nephrectomy. EAbs binding and membrane expression of adhesion molecules ELAM-1,ICAM-1 and VCAM-1 were analyzed by flow cytometry (FACS) and by semi-quantitative RT-PCR for mRNAs coding for those molecules.The absence of anti-HLA antibodies against the donor was ascertained at transplant, before and after nephrectomy by the negativity of lynphocyte crossmatches performed using the must sensitive techniques. EAbs eluted from 8 rejected kidneys bound to HUVEC. They did not induce any cytotoxicity, but their incubation with HUVEC (4 hours at 37C) (2,5mg/ml) led to up-regulation of mRNAs coding for VCAM-1 (35 to 60 fold increases) and ICAM-1 (8 to 12 fold increases) as compared to control EAbs. Membrane expression of these molecules was also strikingly increased, with 80% of the cells expressing VCAM-1 and 65% expressing ELAM-1 upon incubation Eabs were detected in 7 out of 8 (87,5%) eluates form Kidneys lost from acute vascular rejection, but in only one out of 14 (7%) Kidneys lost form other types of rejecton ( p<0,001). We conclude that EAbs, capable of activating human endothelial cells, can be recovered from acutely rejected kidneys and may play a direct role in the pathogenesis of acute vascular rejection.