Antibodies against nucleolin in recipients of organ transplants

Background.: Patients who reject allografts frequently make strong antibody responses against donor human leukocyte antigens and autoantigens such as vimentin, collagen V, or alpha-tubulin and it has been postulated that autoantibodies may play a role in allograft failure. Methods.: We have used serum from patients who recently rejected an allograft as a source of antibodies in combination with lysates of human umbilical vein endothelial cells as a source of target antigens. Immunoprecipitation and protein identification was performed by mass spectrometry. Recombinant nucleolin was produced and sera were assayed for antibodies by enzyme-linked immunosorbent assay. Results.: Immunoprecipitation with serum WW led to the recognition of the protein nucleolin as a target antigen. By enzyme-linked immunosorbent assay, with recombinant nucleolin (r-nucleolin), the frequency of antibodies to nucleolin were found to be 2.0% in normal subjects, 9.1% in patients waiting for a kidney transplant, 25.5% after irreversible rejection of a kidney allograft, 17.1% after a heart transplant, and 43.8% in heart transplant recipients developing transplant-related coronary artery disease. Antibodies against nucleolin from mice or from transplant patients inhibited endothelial cell proliferation and in vitro capillary-like tube formation and caused apoptosis of human umbilical vein endothelial cells. Conclusions.: Antibodies against nucleolin seem to inhibit and produce apoptosis of proliferating endothelial cells. These antibodies were found in many transplant patients and seemed to be associated with rejection of kidney allografts and with coronary artery disease in heart transplant recipients.