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 lymphocytes. Therefore, EL4 cells were seeded into 96-well plates at a density of 8,000 cells/well with 5% serum standard DMEM including various concentrations of recombinant rat IFN-γ. After incubated for 72h, cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8 (CCK-8). Briefly, 10 µl of CCK-8 solution was added to each well of the plate, then the absorbance at 450 nm was measured using a microplate reader after incubating the plate for 2 hours at 37 ℃. Cell viability was assessed by CCK-8 (Cell Counting Kit-8 ) assay after incubation with recombinant rat IFN-γ for 72h. The result was shown in Figure 1. It was obvious that IFN-γ significantly inhibit cell viability of EL4 cells. The ED50 is 1.41μg/mL.