explants [99] . The short incubation time and possibility to repeat the stimulation suggested a non-toxic mechanism. MBP, which is almost as basic as ECP, in the same assay, showed the opposite effect; therefore these effects on mucus secretion are unlikely to be due to electrostatic charge. ECP at these moderate levels (2.5 μg/mL) displayed the same effect on human trachea [99] . However human primary epithelial cells underwent necrosis at higher levels (10 μg/mL) in another study [80] . ECP has also been shown to acting directly on airway mucus in vitro. At high levels (100 μg/mL) ECP altered bovine mucus three fold, as measured by a capillary surfactometer 