TNF-α, Not CD154 (CD40L), Plays a Major Role in SEB-Dependent, CD4+T Cell-Induced Endothelial Cell Activationin Vitro

CD4+T cell effector molecules, in particular TNF-α and CD154, activate endothelial cells. However, the relative contributions of TNF-α and CD154 in mediating endothelial cell activation during complex Ag-driven CD4+T cell–endothelial cell interactions are not known. We utilized anin vitromodel of CD4+T cell–endothelial cell interactions to characterize the contributions of TNF-α and CD154 in mediating upregulation of adhesion molecules CD54, CD62E, and CD106 on human umbilical vein endothelial cells (HUVEC). HUVEC were first treated with IFN-γ to upregulate MHC Class II expression. IFN-γ minimally effects HUVEC adhesion molecule expression but renders them capable of MHC class II restricted interactions with CD4+T cells. Coculturing MHC class II+HUVEC and CD4+T cells with the superantigen SEB induces a rapid and marked upregulation of CD54, CD62E, and CD106 expression on HUVEC, as shown by FACS analysis. To study the effector molecules mediating SEB-driven, CD4+T cell-dependent endothelial cell activation, similar experiments were performed in the presence of neutralizing anti-CD154, anti-TNF-α, or anti-IL1 antibodies, as well as combinations of these antibodies. In contrast to the anti-CD154 or anti-IL-1 antibodies, the anti-TNF-α mAb markedly inhibited SEB-dependent, CD4+T cell-induced HUVEC activation. We conclude that TNF-α, not CD154, plays the major role in SEB-driven, CD4+T cell-induced endothelial cell activationin vitro.