Fig. 1. Cbl-b is upregulated when primary human NK cells are activated by IL-15, IL-2 or K562.

(A) Enriched primary human NK cells were treated with IL-2 (150 IU/ml), IL-7 (50 ng/ml), IL-12 (10 ng/ml), IL-18 (10 ng/ml), IL-21 (20 ng/ml) or IL-15 (20 ng/ml) for 24 h followed by immunoblot analysis (n=5 donors). Densitometric quantification from five independent experiments shows the ratio of Cbl-b protein to β-actin protein. (B) Enriched primary human NK cells were co-cultured with the K562 myeloid leukemia cell line (E/T ratio=10:1) for 24 h followed by immunoblot analysis. Summary data are from three independent experiments. (C) Primary human NK cells were treated with different concentrations of IL-15 for 24 h followed by immunoblot analysis (n=5 donors). (D) Equal numbers of purified CD56⁺ human NK cells, CD56^bright NK cells and CD56^dim NK cells were sorted from peripheral blood mononuclear cells isolated by Ficoll, cultured and stimulated with IL-15 (20 ng/ml for 24 h) followed by immunoblot analysis. The data are representative of three independent experiments. Med, medium only; *P<0.05, **P<0.01 by two-tailed unpaired t-test or One-way ANOVA; ns, not significant. Data are presented as mean ± SEM.