Eosinophil protein in airway macrophages: a novel biomarker of eosinophilic inflammation in patients with asthma.
BACKGROUND
Noneosinophilic asthma is common across asthma severities. However, in patients with moderate-to-severe disease, the absence of sputum eosinophilia cannot distinguish between asthmatic subjects with eosinophilic inflammation controlled by corticosteroids versus those in whom eosinophilic inflammation is not a component of the disease.


OBJECTIVE
We sought to develop a method to quantify eosinophil proteins in airway macrophages as a novel biomarker of eosinophilic airway inflammation.


METHODS
Eosinophil proteins in airway macrophages were assessed by means of flow cytometry, immunofluorescence, and cytoplasmic hue change after ingestion of apoptotic eosinophils. Airway macrophage median percentage of red-hued area in stained sputum cytospin preparations was assessed by means of image analysis from (1) subjects with mild-to-severe asthma, subjects with nonasthmatic eosinophilic bronchitis, and healthy control subjects; (2) subjects with eosinophilic severe asthma after treatment with prednisolone; and (3) subject with noneosinophilic asthma before corticosteroid withdrawal.


RESULTS
Eosinophil proteins were detected in airway macrophages, and cytoplasmic red hue increased after ingestion of apoptotic eosinophils. Airway macrophage percentage redhued area was increased in subjects with moderate-to-severe asthma compared with that seen in subjects with mild asthma and healthy control subjects, was similar in those with or without a sputum eosinophilia, and was increased after corticosteroid therapy. In asthmatic subjects without sputum eosinophilia, the airway macrophage percentage red-hued area was increased in subjects who did versus those who did not have sputum eosinophilia after corticosteroid withdrawal.


CONCLUSIONS
Eosinophil proteins can be reliably measured in airway macrophages. In combination with sputum eosinophilia, the macrophage eosinophil protein content might further define the asthma phenotype and provide an additional tool to direct therapy.
Kulkarni
Neeta S
NS
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.|Children's Community Health Service, Leicester City NHS Primary Care Trust.
Hollins
Fay
F
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Sutcliffe
Amanda
A
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Saunders
Ruth
R
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Shah
Sachil
S
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Siddiqui
Salman
S
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Gupta
Sumit
S
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Haldar
Pranab
P
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Green
Ruth
R
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Pavord
Ian
I
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Wardlaw
Andrew
A
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
Brightling
Christopher E
CE
Institute for Lung Health, Glenfield Hospital, Leicester, and the Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000328:Adult; D017209:Apoptosis; D001249:Asthma / Q000150:complications* / Q000188:drug therapy / Q000378:metabolism; D015415:Biomarkers; D003430:Cross-Sectional Studies; D047150:Eosinophil Cationic Protein / Q000032:analysis*; D047209:Eosinophil Peroxidase / Q000032:analysis*; D004802:Eosinophilia / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008264:Macrophages / Q000737:chemistry*; D008297:Male; D008875:Middle Aged; D013183:Sputum / Q000737:chemistry / Q000166:cytology
D000305:Adrenal Cortex Hormones; D015415:Biomarkers; D047209:Eosinophil Peroxidase; D047150:Eosinophil Cationic Protein; C479220:RNASE3 protein, human