I have stimulated thp-1 cells and applied inhibitor but the inhibitor did not work and I am wondering why would this coul happened, could it be because of the FBS ?
Yes, probably you may be right. Inhibitory components of FBS could be responsible.10% FBS present in the medium contains enough TGF-β to inhibit macrophage activation. Thus, culturing macrophages in standard FBS-containing medium may be misleading because TGF-β1 inhibits macrophage activation. For more details you may refer to the research article attached below.