Quantification of pulmonary uptake of indium-111 labelled granulocytes in inflammatory bowel disease

Labelling of leucocytes with technetium-99m exametazime causes in vitro upregulation of granulocyte CD11b without correlation to tissue uptake in vivo

The aims of this study were to investigate whether labelling with technetium-99m exametazime alters the expression of adhesion molecule CD11b on granulocytes and monocytes, and to study whether the expression of CD11b on unlabelled or labelled cells correlates with uptake of the labelled cells in the inflamed bowel, in the lungs or in the reticuloendothelial system. Leucocytes were obtained from 25 patients with inflammatory bowel disease who underwent leucocyte scan. The cellular expression of CD11b was analysed using flow cytometry. Labelling with 99mTc-exametazime induced an increased surface expression of CD11b on granulocytes (P<0.01), but not on monocytes. The increase in CD11b expression on granulocytes was lower than the spontaneous mobilization that occurred at 37 degrees C and correlated neither with this, nor with N-formyl-methionyl-phenylalanine induced expression of the same receptor. Basal expression of CD11b on unlabelled granulocytes, but not on monocytes, correlated with bowel and lung uptake 45 min after reinjection of labelled cells, but not with uptake on later images. No correlation was found between the CD11b expression on labelled granulocytes or monocytes and scintigraphic uptake. Our findings show that labelling with 99mTc-exametazime increases the expression of adhesion protein CD11b on granulocytes. The increase in surface expression of CD11b does not correlate with the scintigraphic uptake of labelled cells in the bowel, in the lungs or in the reticuloendothelial system.

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