In-111-labelled leukocyte migration to the lungs of ovalbumin-sensitized guinea-pigs after aerosol challenge with ovalbumin monitored by gamma scintigraphy

Background: To determine whether antigen challenge is associated with incre ased accumulation of leukocytes in the lungs, the pulmonary accumulation of In-111-labelled neutrophils and eosinophils was monitored by gamma scintig raphy, Methods: Guinea-pigs were sensitized with ovalbumin (OA) 14-21 days before challenge with aerosolized OA (10 mg/ml) for 2 min, and protected ag ainst fatal anaphylaxis by mepyramine (30 mg/kg). Comparisons were made wit h OA-sensitized guineapigs 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. 2M Bq Tc-99m macroaggregated albumin (MAA) was injected intravenously to creat e a pulmonary perfusion image as a template for the lungs. In-111-labelled neutrophils or eosinophils were then injected via the carotid artery and ga mma scintigraphic images obtained. Activity in the lung region of each anim al was determined by superimposing the (99m)TcMAA image of the lungs on the whole body image. Results: A significant increase in activity (p<0.05) in the lung region was observed after injection of In-111-labelled neutrophils at 5 h after the OA challenge compared with saline challenge. 24 h after O A challenge there was a significant increase in activity (p<0.05) in the lu ng region after injection of In-111-labelled eosinophils, but no change in activity after injection of labelled neutrophils compared with the saline-c hallenged animals. Conclusion: This technique models the migration of leuko cyte to the lungs seen in guineapigs in our previous studies, namely an eos inophilia at 24 h and a neutrophilia at 5 h after OA challenge. It will the refore be useful for investigating anti-inflammatory drugs on the airways.