Background Eosinophils are key mediators of allergic inflammation.
The ability to localise and quantify eosinophilic
inflammation in vivo would facilitate patient endotyping and
evaluation of eosinophil-targeted therapeutics. We aimed to
quantify eosinophil distribution and organ-specific uptake in
healthy subjects, asthmatics, and patients with focal pulmonary
eosinophilic inflammation.
Methods We injected autologous radiolabelled eosinophils into 8
healthy volunteers, 15 asthmatics (7 obese and 7 non-obese), and
3 patients with focal eosinophilic inflammation and monitored
eosinophil distribution (planar imaging, single photon emission
computed tomography – SPECT)/CT). Lung accumulation of technetium-
99 m-labelled eosinophils was quantified (Patlak-Rutland
analysis). Whole body indium-111-labelled eosinophil distribution
and loss were further assessed in 5 healthy volunteers and 7 asthmatics
using a whole body counter.
Findings Pulmonary eosinophil clearance was increased in
patients with focal eosinophilia (0·0033 ml/min/ml; 95% CI
0·005–0·011; p=0.02) compared to asthmatics (0·0007 ml/
min/ml; 95% CI 0·0003–0·0010; p=0.14) and controls
(0·0003 ml/min/ml; 95% CI 7·5 × 10–5–0·0008). Absolute
lung eosinophil migration was elevated in patients with focal
inflammation (5932 eosinophils/min/ml; 95% CI 14351–
26215, p=0.01) and asthma (364 eosinophils/min/ml; 95% CI
38–689; p=0.03) versus healthy volunteers (38 eosinophils/
min/ml; 95% CI 11–87). Stratification of asthmatics based
on BMI revealed increased pulmonary eosinophil clearance in
obese (0·001 ml/min/ml; 95% CI 0·0007–0·001; p=0.02) versus
non-obese asthmatics (0·0003 ml/min/ml; 95% CI
0·0002–0·0009).
Interpretation Eosinophil radiolabelling can quantify pulmonary
eosinophilic inflammation, with the potential for patient endotyping
and testing eosinophil-targeted treatments.
Funding Medical Research Council, Wellcome Trust, Asthma
UK, Cambridge NIHR Biomedical Research Centre
