Antithymocyte Globulins Bind to Human Umbilical Vein Endothelial Cells

Objective. Polyclonal antithymocyte globulins (ATGs) are immunosuppressive agents used for the treatment of organ rejection after transplantation. ATGs induce complement-mediated cell death of T lymphocytes and may decrease leukocyte adhesion. However, little is known about their effects on endothelial cells (ECs). Our aim was to study whether they bind to human umbilical vein endothelial cells (HUVECs). Materials and Methods. HUVECs obtained from umbilical cords were cultured and incubated with ATGs. A group incubated without ATG served as controls. All groups were coincubated with an anti-rabbit-IgG. Binding of ATGs to HUVECs was investigated by means of flow cytometry. Statistical analysis was performed using one-way analysis of variance (ANOVA). Results. ATGs were bound to HUVECs with or without prior stimulation by tumor necrosis factor-alpha (TNF-alpha). Binding of ATGs to HUVECs was >99% in all treated groups. The mean intensity of fluorescence was constant in the ATG-treated groups. Conclusions. Our results demonstrated that ATGs bind to HUVECs before and after stimulation with TNF-alpha. Binding of ATGs to HUVECs suggests an independent endothelial mechanism of ATG action.