Presence of c-Kit is crucial for an effective IL-33–induced signaling. (A) Surface expression of IL-33R and c-Kit in wt (black line) or kit^W-sh/W-sh (black dotted line) BMMCs. (B-C) Wt or kit^W-sh/W-sh BMMCs were stimulated with IL-33 as indicated. Lysates were analyzed by immunoblot for phosphorylated signaling molecules as indicated (B). Longer exposure shows that IL-33–induced activation of JNK1 in kit^W-sh/W-sh BMMCs is dramatically reduced but not completely blocked. Phosphorylation was quantified in 3 independent experiments and results are shown as increase (mean ± SEM) relative to nonstimulated wt BMMCs. Supernatants were analyzed for IL-6 (C).