Background: A variety of cytokines, mediators, activators, growth factors and other products are simultaneously released into circulation with the activation of the cellular immune system during rejection or infection. The secretion of these biochemical markers potentiates the immunological events associated with these processes. Among other things some cytokines demonstrate regulatory effects on the expression of endothelial cell adhesion molecules.
Method: Endothelial cells are detached by trypsinisation and adhesion molecule expression is assessed by means of flow cytometry. Fluorescence-conjugated mouse monoclonal antibodies directed against VCAM-1, ICAM-1, PECAM-1, CD34, E- and P-selectin are used.
Results: The combined application of different cytokines synergistically evokes P-selectin expression after a chosen incubation period of 16 h, while under single cytokine treatment P-selectin induction is not observed. Co-stimulation with TNF-alpha and a second cytokine reduces its influence on E-selectin. IL-1 beta/IFN-gamma lead to E-selectin levels higher than those under treatment with one of the both alone. Concomitant incubation with all cytokines synergistically down-regulates PECAM-1 referred to each cytokine alone.
Conclusion: Our investigations in some cases clearly demonstrate that the combination of a second cytokine with TNF-alpha, IL-1 beta or IFN-gamma can either synergistically or antagonistically modulate the expression of adhesion molecules on HUVECs.