The effect of IL-4C pretreatment on α-GalCer-induced cytotoxicity and prevention of lung metastasis. α-GalCer (2 μg) or vehicle was intravenously injected into IL-4C-pretreated or untreated (cont.) mice. After 24 hours, cytotoxicity of the spleen cells against (A) YAC-1, (B) P815, (C) RenCa, or (D) CT26 was measured by a 4-hour ⁵¹Cr-release assay. Each symbol represents the mean ± SE of 3 independent experiments. Statistical significance was calculated by Student t test (^*P < .05; ^**P < .01 vs. cont.). (E) IL-4C- or PBS (cont.)-pretreated mice were intravenously injected with 5 × 10⁵ RenCa cells with or without 2 μg α-GalCer. After 3 weeks, the number of lung metastases was counted. Each column represents the mean ± SE of 5 individuals. Statistical significance was calculated by Student t test (^**P < .01). (F) Representative views of lung metastasis in nontreated (cont.), IL-4C-treated, α-GalCer-treated, and IL-4C plus α-GalCer-treated mice.