DISSOCIATION OF NEUTROPHIL EMIGRATION AND METABOLIC-ACTIVITY IN LOBARPNEUMONIA AND BRONCHIECTASIS

In animal models of pulmonary inflammation, neutrophils exhibit a dram atic influx of glucose in periods of high metabolic activity, This inf ormation was utilized to develop a technique, involving positron emiss ion tomography (PET) of 2-[F-18]-fluoro-2-deoxy-D-glucose ((18)FDG), w hich measures neutrophil activity in situ. This technique was applied in a comparative study of neutrophil function in patients with acute l obar pneumonia or bronchiectasis, Neutrophil emigration was measured b y gamma-scintigraphy of intravenously injected In-111-labelled granulo cytes and neutrophil activity determined by PET of (18)FDG. Neutrophil emigration was evident in 4 out of 5 bronchiectasis patients, whilst no emigration was apparent in the two pneumonia patients studied, cons istent with animal studies showing maximum emigration soon after chall enge, In contrast, (18)FDG uptake was markedly increased in 4 out of 5 pneumonia patients but not in the patients with bronchiectasis. Local ization of radioactivity to neutrophils was confirmed by microautoradi ography of lavage fluid in a patient with pneumonia, These results sug gest that the elevated uptake of glucose by neutrophils during the inf lammatory response is a postmigratory event, most likely reflecting th e respiratory burst, and that high levels of neutrophil emigration are not necessarily associated with significantly increased metabolic act ivity of these cells.