Fig. 1

Skeletal muscle cells express IL-15/IL-15Rα protein complex in response to TNF-α and IFN-γ stimulation. a Expression of Il15 and Il15ra mRNA during C2C12 myoblast differentiation. Samples were collected before (0) and 2, 4, and 6 days after differentiation induction. b Expression of Il15 and Il15ra mRNA in C2C12 myotubes treated with TNF-α (10 ng/ml), IFN-γ (10 ng/ml), TNF-α + IFN-γ (TNF + IFN, 10 ng/ml each), or without cytokine (con) for 1, 2, 3, 6, 12, and 24 h. c Expression of Il15 and Il15ra mRNA in primary myotubes treated with TNF-α (5 ng/ml), IFN-γ (5 ng/ml), TNF + IFN (5 ng/ml each), or without cytokine (con) for 24 h. d Expression of IL-15/IL-15Rα complex protein in C2C12 myoblasts and myotubes treated with TNF-α (1 or 10 ng/ml), IFN-γ (1 or 10 ng/ml), TNF + IFN (1 or 10 ng/ml each), or without cytokine (con) for 24 h. e Expression of IL-15/IL-15Rα complex protein in primary myotubes treated with TNF + IFN (5 ng/ml each) or vehicle (con) for 24 h. f Expression of IL-15/IL-15Rα complex protein in skeletal muscle in vivo. TNF-α plus IFN-γ (1 mg each/injection) or PBS (con) was injected into the quadriceps muscles of mice three times at 4-h intervals. The injected muscles were collected 16 h after the last injection. Total RNA was isolated and analyzed by qPCR (a–c). Protein lysate and cell culture medium were collected and measured by ELISA (d–f). Data in (a–c) were triplicates and representative of two independent experiments with similar result. Data in (d, e) were pooled from three independent experiments. Data in (f) was pooled from three mice in each group. Data are mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001, in comparison to “0” or “con”