The role of PAR2 in allergic lung inflammation. Different sources of PAR2-activating proteases (both host-derived and allergen-derived) in allergic lung inflammation cause PAR2 activation on eosinophils, airway epithelial cells, and airway smooth muscle. PAR2 has been implicated as the molecular link between these proteases (including FXa and FVIIa) and allergic lung inflammation.