Naïve HC15 cells were transfected with no siRNA (Mock), siRNA against Lyn (si-Lyn) or negative control siRNA (Neg. si) for 48 hr as detailed under Materials and Methods. The expression levels of Lyn were examined by immunoblotting (A, upper panel) and summarized as the mean ± (SEM) from four independent experiments (A, lower panel). Following Lyn knockdown for 48 hr, the cells were treated with 1 nM IL-3 for 1 hr and then stimulated with 100 nM fMLP for 2 min. Representative immunoblots of pERK1/2 and actin (B, upper panel), and the summary of the mean ± (SEM) from four independent experiments (B, lower panel) are shown. *p<0.02, N=4.