Allergenic extracts from HDMA (Der f) induced phosphorylation of p44/p42 MAPK. Following exposure of A549 cells to HDMA (25 μg/ml), at the indicated time points, total protein extracts were immunoblotted with antibodies specific for phosphorylated and non-phosphorylated p44/p42 MAPK. Phospho-p44/p42 MAPK bands were quantified by densitometry and normalized to total p44/p42 MAPK. The experiment was repeated twice. A representative experiment is shown.