IFN-γ is a dimerized soluble cytokine that is the only member of the type II class of interferons. The importance of IFNγ in the immune system stems in part from its ability to inhibit viral replication directly, and most importantly from its immunostimulatory and immunomodulatory effects. As reported, IFNγ is an important activator of human monocytic THP1 cells. Therefore, THP-1 cells were incubated in RPMI 1640 with various concentration of IFN-γ, then cells were observed by inverted microscope everyday. After stimulated with IFN-γ (2ng/mL) for 5 days, morphological changes occurred in THP1 cells which displayed the shape of fusiform or polygon and were more likely to adhere. Effect of IFN-γ on THP1 cells is shown in Figure 1.