Airway responses to platelet-activating factor.

Platelet-activating factor is a potent mediator, with numerous biologic activities. It is capable of inducing both acute bronchoconstrictor responses in the lung in addition to increasing airway responsiveness to non-specific factors. It is this latter property that is especially intriguing since no other mediator of immediate hypersensitivity has been demonstrated to have such striking properties. The recent demonstration of induction of persistent (as long as 2 wk) airway hyperresponsiveness in humans after aerosolized PAF is an exciting development in our understanding of potential mediators of this entity. Much remains to be defined regarding the role of PAF in bronchial asthma including the cellular source of its production, the dependence of its effect upon other cell types such as platelets and polymorphonuclear leukocytes, the secondary mediator or mediators released from recruited cells, which are involved in producing the final pathophysiologic picture, and the mechanism by which altered airway responsiveness occurs.