The in vivo behavior of granulocytes labeled with indium-111 in a canine model of pneumococcal pneumonia.

Use of [111In]granulocytes in the study of pulmonary inflammation requires study of their in vivo behavior. To study the pulmonary deposition of these cells and their ability to migrate from the capillary to the alveolus, we injected [111In]granulocytes into dogs 24 h after the induction of a right lower lobe pneumococcal pneumonia. Using external imaging, we found rapid clearance of [111In]granulocytes from the uninvolved lung (with a residual radioactivity of 24.5 +/- 4.2% at 4 h). In contrast, 83 +/- 12.4% of the initial radioactivity was present in inflamed lung at 4 h. Bronchoalveolar lavage fluid from the inflamed lung was more cellular than that from control lung, contained a greater fraction of polymorphonuclear leukocytes (82 +/- 4.1% versus 20 +/- 6.2%), and much greater cell-associated radioactivity (ratio of 423:1, inflamed to control). Autoradiography disclosed that this radioactivity was localized to consolidated alveoli and was not prominently distributed in arterioles or venules or in airways larger than 0.6 mm. We conclude that [111In]granulocytes are biologically active in the setting of acute lung inflammation.

The labeling of rabbit neutrophils with [111In]oxine.

We report here the successful labeling of rabbit peripheral blood neutrophils with [111In]oxine. We found that standard techniques for preparation of rabbit neutrophils, while acceptable for maintenance of in vitro function, rendered the neutrophils ineffective for in vivo use after labeling with 111In. Specifically, rabbit neutrophils were sensitive to the use of hypotonic shock for red cell elimination, centrifugation into a button during preparation, and the presence of oxine during chemotaxis in vitro. Using a carefully modified method of neutrophil preparation and labeling, we found that 111In-labeled rabbit neutrophils retained normal in vitro function, including chemotaxis. In addition, using our method, 34% +/- 5% of labeled neutrophils were recoverable in peripheral blood 5 min after intravenous injection. The half-life of circulating radio-labeled neutrophils was 5.6 +/- 2 h. Continuous external imaging of radio-labeled neutrophils after intravenous injection showed initial lung uptake, followed by rapid clearance of radioactivity in the lungs (50% clearance in 10.5 +/- 3.3 min.) Hepatic radioactivity was maximal by 30 min after injection and thereafter slowly declined. Finally, we found that 111In-labeled rabbit neutrophils migrated to sites of artificially induced inflammation. Our findings indicate that 111In-labeled rabbit neutrophils, if prepared under optimal conditions, should provide a useful tool for investigating the fate of neutrophils in experimental inflammatory conditions in this animal.