['We have previously demonstrated that the administration of nerve growth factor (NGF) to guinea-pigs results in airway hyper-responsiveness within 1 h.', 'In the present study we document the involvement of NGF in the acute allergic airway response.', 'Guinea-pigs that are sensitized to ovalbumin show an acute bronchoconstriction directly after challenge with ovalbumin.', 'Intratracheal application of 10 microg of antibodies directed against NGF (anti-NGF) 1 h before the challenge reduces the acute severe bronchoconstriction to approximately 40% and the sustained bronchoconstriction to approximately 20% of the reaction in controls. This shows a high potency of anti-NGF in diminishing the direct bronchoconstriction. Inhibition of the tyrosine kinases of the tyrosine kinase receptor A, the high-affinity receptor for NGF, has no effect on the bronchoconstriction. Therefore, we postulate that the p75, the low-affinity receptor for neurotrophins, is responsible for the acute bronchoconstriction. Our findings suggest a role for NGF in the induction of the acute asthmatic reaction.'] Do antibodies directed against nerve growth factor inhibit the acute bronchoconstriction due to allergen challenge in guinea-pigs?