Assessment of ERK1/2 phosphorylation after eotaxin and LTB₄ stimulation. Pirb^−/− or wild-type (WT) eosinophils were stimulated with eotaxin-2 (10 ng/mL; A,C) or LTB₄ (10 nM; B,D) at the indicated time points. Thereafter, the cells were lysed, analyzed by SDS-PAGE, transferred to a membrane, and blotted with antibodies to phospho-specific ERK1/2 (pERK1/2) or total ERK1/2 as loading control. Quantification of band intensity (C,D) of eotaxin and LTB₄ stimulated eosinophils. Each time point was normalized to the baseline phosphorylation state of WT mice and presented as fold increase plus or minus SD. Data represent n = 3 experiments; *P < .05; **P < .01; ***P < .001 when comparing WT and Pirb^−/− cells.