Molecular identification of endothelial cell surface antigens using proteomic approach to the molecules recognized by antibodies in transplant recipients (TRAN1P.939)

Abstract

Abstract It is known that transplant recipients may have antibodies to endothelial cells (EC) but not to lymphocytes, by which the rapid and irreversible destruction of allograft is induced. We characterize EC surface antigens using well-identified recipient sera with strong antibodies against EC. 9 serum samples from 7 patients with kidney allograft rejection and antibodies against freshly isolated human umbilical vein endothelial cells (HUVECs) were selected. Target antigen proteins of EC were immunoprecipited by serum antibodies and separated by SDS/PAGE, followed by protein identification with mass spectrometry. Monoclonal antibodies against HLA and MICA were used as the procedure control in our experiment. We successfully captured the HLA and MICA molecules from ECs by these mAbs respectively. Using patient sera, three proteins were identified in these experiments: 1) human MICA glycoproteins, already known surface molecules expressed on ECs and associated with antibody-mediated rejection; 2) human keratin 1, a protein known to be expressed on the surface of endothelial cells; 3) 70KDA (local name) molecule, a protein underwent investigation. A variety of antigens appears to be harbored on the surface of endothelial cells and can elicit immune responses in transplant recipients. Our results indicated that MICA, keratin 1 and 70KDA proteins might be important antigens in organ transplant rejection. The role of these molecules on transplant rejection requires further investigation.