Fibronectin maintains the survival of mouse NK cells in vitro. (A) DX5⁺ natural killer (NK)–cell populations isolated from splenocytes of wild-type mice by magnetic-activated cell sorting were cultured in the presence or absence of fibronectin (FN, 10 μg/mL) or IL-15 (10 ng/mL), then labeled with annexin V and 7-amino-actinomycin D and assessed for their viability by FACS at the indicated times. (B) NK cells were cultured in the presence of fibronectin at different concentrations and their viability was detected using FACS 24 hours later. (C-D) NK cells were cultured for 24 hours in the presence of 10 μg/mL fibronectin and then CD69 expression on the NK cells was tested using FACS (C) and the level of IFN-γ in the supernatant was detected by cytometric bead array technology (D). (E) NK cells were cultured in the presence of 50 μg/mL fibronectin and then IFN-γ was detected 24 hours later. All data are shown as the mean ± SD of 3 independent experiments.