Induction of tissue factor expression on human umbilical vein endothelial cells by cell-specific HLA class I...

Donor-specific antibodies may play an important role in the development of chronic allograft rejection process. However, the mechanisms leading to intimal vascular proliferation and fibrosis remain poorly understood. The aim of this study was to examine whether donor-specific HLA antibodies induce overexpression of tissue factor (TF) by endothelial cells. HLA typed human umbilical vein endothelial cells (HUVEC) were incubated for 1 to 12 hours with LPS (10 microg/mL), and increasing concentrations (1 to 500 microg/mL) of anti-HLA A1 antibody specific for an antigen expressed by HUVEC and of an anti-HLA A2 antibody for which A2 was not expressed by the HUVEC. Expression of TF mRNA transcripts was quantified using real time Q-RT PCR and TF activity was tested in cell lysates of cultured HUVEC using a chromogenic TF activity assay. HUVEC-specific anti-HLA A1 antibody at low concentrations (10 microg/mL) induced both a significant increase of TF mRNA transcripts after 1 hour of incubation and TF activity after 3 hours incubation compared to incubation with medium alone or with the nonspecific anti-HLA A2 antibody (n = 4 for all experiments, P < .05). These data show for the first time that specific anti-HLA antibody can induce overexpression of TF on endothelial cells. TF, a transmembrane glycoprotein involved not only in the onset of the coagulation cascade, but also in cell proliferation and anti-apoptotic processes, may play a role in the development of alloantibody-induced chronic rejection.