Two week exposure to IL-4 or IL-13 does not affect the release of the antimicrobial proteinase inhibitors SLPI or elafin. PBEC from six different donors were cultured at an ALI for 14 days in the presence of 1, 10 or 20 ng/ml of IL-4 or IL-13. (A) Basal medium (black bars) and apical washes (gray bars) were harvested and analyzed for SLPI (upper panel) and elafin (lower panel) protein levels using sandwich ELISA. Data are presented as mean ± SEM from experiments performed in duplicate (- n = 8; IL-4 1 ng/ml n = 3; IL-4 10 ng/ml n = 8; IL-4 20 ng/ml n = 7; IL-13 1 ng/ml n = 3; IL-13 10 ng/ml n = 3; IL-13 20 ng/ml n = 2). (B) Quantitative real time PCR for SLPI and elafin mRNA expression. Data are mean ± SEM of fold increase compared to medium alone for 4 independent experiments. Data were normalized for expression against two reference genes (β-actin and GAPDH).