CD40L-CD40 interactions regulate endothelial cell surface tissue factor and thrombomodulin expression

During immune responses, activated endothelial cells down-regulate thrombomodulin and up-regulate tissue factor expression leading to the development of a procoagulant surface, CD4(+) T cells are known to promote endothelial cell procoagulant activity, however, the molecular interactions that mediate this effect are not completely known. CD40L is an activation-iuduced CD4(+) T cell surface molecule that functionally interacts with CD40 expressed on endothelial cells, In this study we ask if CD40L-CD40 interactions modulate endothelial cell surface tissue factor or thrombomodulin expression in vitro, Human umbilical vein endothelial cells (HUVEC) were cocultured with control cells or CD40L(+) Jurkat T cells inn the presence or absence of anti-CD40L mAb. By two-color FACS analysis we demonstrated that CD40 Ligation induces HUVEC tissue factor expression and thrombomodulin down-regulation, Utilizing neutralizing antibodies, we show that CD40L-mediated tissue factor and thrombomodulin modulation, as well as E-selectin and VCAM-1 upregulation, is independent of tumor necrosis factor alpha, interleukin-1 alpha, or interleukin-1 beta production, Together these data suggest that CD40L-CD40 interactions may directly regulate endothelial cell procoagulant activity during inflammatory responses.