LIGHT stimulates NK-cell proliferation and activation. (A) Ag104L^d LIGHT tumor cells profoundly induce NK-cell proliferation and IFNγ secretion. Purified NK cells from Rag1^-/- mice were cocultured with irradiated Ag104L^d LIGHT cells for 3 days. ³H-TdR incorporation and IFN-γ detection were described as above. Tumor or NK cells alone do not show much proliferation and cytokine production. Tumor cells with LIGHT can significantly stimulate NK cells (P < .001). The data are presented from 3 independent experiments. (B) Blocking LIGHT disrupts Ag104 L^d LIGHT-mediated NK-cell proliferation and activation. The low dose (5 μg/mL) of LTβR-Ig or control Ig was added to the reaction of NK and Ag104L^d LIGHT-cell culture for 3-day incubation. Significant inhibition was found with LTβR-Ig group over control (P < .001). (C) rLIGHT induces NK-cell proliferation. Purified NK cells were isolated through NK purification kit from Rag1^-/- mice and incubated with rLIGHT-coated plates for 3 days. ³H-TdR was added 15 hours before incorporation assay. rLIGHT can stimulate NK cells (P < .001). (D) rLIGHT enhances IFN-γ and GM-CSF secretion. IFN-γ and GM-CSF were detected with ELISA from the supernatants as treated above. Data analysis was performed by using the Student t test. Averaged results are expressed as mean plus or minus SD.