To assess the roles of IFN-γ and cytotoxicity in NK-dependent-CTLA4Ig-anti-tumor activity in vivo, the B16 melanoma mice treated with either CTLA4Ig or control IgG were sacrificed 10 days after tumor inoculation; magnetic-activated cell sorting (MACS, Miltenyi Biotec) was used to isolate the infiltrating NK cells from lung tissue for the analysis of cytolytic activity and cytokine production. The gene discussed is IFNG; the disease is melanoma.