Figure 3. NKG2D receptor-ligand interaction mediates the recognition of senescent cells by NK cells. Growing and senescent (DIS) IMR-90 fibroblasts were co-incubated with either NK92 (A) or primary NK cells (B) in the presence of different blocking antibodies and the percent of cytotoxicity towards senescent cells was assessed after 2 hours. (C,D) MICA and ULBP2 were knocked down using specific siRNA and knockdown efficiency was evaluated by quantitative RT-PCR. (E) The degree of cytotoxicity of NK92 cells towards senescent cells was assessed following the knockdown of MICA and ULBP2 in senescent or growing (control) cells. Data presented as mean with S.E.M of three independent experiments. *P<0.05, **P<0.001, ***P<0.0001.