Measuring whole-body neutrophil redistribution using a dedicated whole-body counter and ultra-low doses of 111Indium

Background - There is increasing interest in the ‘homing’ of neutrophils to bone marrow. The aim of this study was to measure the whole-body redistribution of 111In using a whole-body counter following the administration of ultra-small activities of 111 In-labelled neutrophils. Methods - The detectors of a dedicated whole-body counter were fitted with lead collimators. Whole-body 111 In distribution was recorded at 45 min, 24 h, and 2, 4, 7 and 10 days after administration of 111 In-labelled neutrophils (0.29–0.74 MBq) in eight healthy non-smokers, five healthy smokers, eight patients with inactive bronchiectasis, three with asthma and nine with chronic obstructive pulmonary disease (COPD). Results - Intravascular 45-min 111In-labelled neutrophil recovery was not significantly different between groups, ranging from 33 (SD 8%) in healthy smokers to 45 (14%) in healthy non-smokers (P > 0.05). Peaks were identified on the whole body count profile corresponding to the chest, upper abdomen (liver ⁄ spleen) and pelvis (bone marrow). 111 In distribution changed between 45 min and 24 h and then remained stable thereafter. Peak chest counts increased ~ 1.5-fold between 45 min and 24 h, whereas upper abdominal peak counts decreased by ~ 25% with no significant inter-group differences. The increment in pelvic counts (~2.7-fold) was similar between groups, except COPD patients, in whom it was 2.04 (0.35; P Conclusions - Assuming neutrophils are distributed only between blood, liver, spleen and bone marrow, the data suggest that marrow pools 25% and destroys 67% of circulating neutrophils, rising in COPD to 40% and 80%, respectively, possibly as a result of the effects on marrow of chronic hypoxaemia.