111In–Labelled Leukocyte Migration to the Lungs of Ovalbumin–Sensitized Guinea–Pigs after Aerosol Challenge with Ovalbumin Monitored by Gamma Scintigraphy

Abstract

Background: To determine whether antigen challenge is associated with increased accumulation of leukocytes in the lungs, the pulmonary accumulation of ¹¹¹In–labelled neutrophils and eosinophils was monitored by gamma scintigraphy. Methods: Guinea–pigs were sensitized with ovalbumin (OA) 14–21 days before challenge with aerosolized OA (10 mg/ml) for 2 min, and protected against fatal anaphylaxis by mepyramine (30 mg/kg). Comparisons were made with OA–sensitized guinea–pigs challenged with saline. 5 or 24 h following the OA challenge, guinea–pigs were anaesthetized and the jugular vein and right carotid artery were cannulated, with the contralateral artery tied off. 2MBq ^99mTc macroaggregated albumin (MAA) was injected intravenously to create a pulmonary perfusion image as a template for the lungs. ¹¹¹In–labelled neutrophils or eosinophils were then injected via the carotid artery and gamma scintigraphic images obtained. Activity in the lung region of each animal was determined by superimposing the ^99mTcMAA image of the lungs on the whole body image. Results: A significant increase in activitiy (p<0.05) in the lung region was observed after injection of ¹¹¹In–labelled neutrophils at 5 h after the OA challenge compared with saline challenge. 24 h after OA challenge there was a significant increase in activity (p<0.05) in the lung region after injection of ¹¹¹In–labelled eosinophils, but no change in activity after injection of labelled neutrophils compared with the saline–challenged animals. Conclusion: This technique models the migration of leukocyte to the lungs seen in guinea–pigs in our previous studies, namely an eosinophilia at 24 h and a neutrophilia at 5 h after OA challenge. It will therefore be useful for investigating anti–inflammatory drugs on the airways.