Rhesus monkeys were passively sensitized to grass pollen by intravenous injection of human reaginic serum. Sensitized animals, who consistently exhibited local or general anaphylactic reactions following the intradermal, intrabronchial or systemic injection of the specific allergen, tolerated the allergen perfectly well when given it by inhalation. No significant changes in pulmonary resistance, dynamic lung compliance or tidal volume were observed in unanaesthetized, passively sensitized monkeys following administration of an aerosol containing pollen. An increase in respiratory rate was noted immediately after aerosolization in sensitized and unsensitized monkeys.
Inhalation of histamine in some animals exerted a bronchoconstrictor effect which was promptly relieved by administration of a sympathicomimetic bronchodilator. A positive test with histamine was characterized by symptoms of dyspnoea, auscultatory findings of wheezing rates and by a significant increase in pulmonary resistance. These results suggest that sensitization of the bronchi by reagins per se cannot explain the occurrence of bronchospasm upon inhalation of the allergen. Other local or general factors may be required to produce the clinical expression of the bronchial anaphylactic reaction.