Development of a method for monitoring the migration of 111In-labeled eosinophils and neutrophils to the lungs of anaesthetized guinea pigs by gamma scintigraphy and bronchoalveolar lavage.

A method to introduce 111In-labelled neutrophils or eosinophils into the circulation of anaesthetized, ovalbumin-sensitized guinea pigs and monitor their pulmonary accumulation using gamma scintigraphy has been developed. The method is based on the ability to use 99mTc macroaggregated albumin (MAA) to create a pulmonary perfusion image as a template for the lungs of individual guinea pigs which can be superimposed on to the image produced by the 111In-labelled leukocytes injected into the same animal. Intravenous injection of the labelled leukocytes was shown to produce a high density radioactivity in the heart and lungs with little circulation to the rest of the body. This suggested an immediate 'trapping' of leukocytes in the pulmonary vascular bed. A more effective distribution of 111In-labelled cells was achieved by injecting them into the right carotid artery. This ensured more efficient circulation of the cells and resulted in their appearance in the lungs, liver and spleen. However, it was found that the contralateral carotid artery had to be tied off to prevent the cells only circulating to the superior left quadrant of the animal. Bronchoalveolar lavage of the lungs following i.v. injection of 111In-labelled neutrophils showed no significant difference in radioactivity of lavage fluid between guinea pigs challenged 24 h beforehand with inhaled saline or ovalbumin. In contrast, when labelled eosinophils were injected, there was a significantly greater mean radioactivity level in lavage fluid after ovalbumin challenge than after saline. In conclusion, gamma scintigraphy provides an accurate measure of the amount of activity from 111In-labelled leukocytes in the lung region which is specific for each animal