IFN-g is a?dimerized?soluble?cytokine?that is the only member of the type II class of interferons. The importance of IFNg in the immune system stems in part from its ability to inhibit viral replication directly and most importantly from its immunostimulatory and immunomodulatory effects. The activity of recombinant human IFN-g measuerd by inhibit HIV-1-GFP lentiviral infection HUVEC cells. HUVEC cells were seeded into triplicate wells of 96-well plates at a density of 4,000 cells/well with 10% serum standard DMEM?, after the cells adhesion, repalce the medium with various concentrations of recombinant human IFN-g, incubate overnight at 37℃. Then suction out the DMEM medium, add lentiviral?particles 100 μl to each well, incubate 24h at 37℃, change fresh 10% serum standard DMEM to the well, continuing incubate at 37℃for 96h. The results observed by inverted microscope was shown in Figure1. The ED50 for this effect is 0.01 ug/ml