Abstract
BackgroundLocal IgE production may play a role in asthma pathogenesis. The aim of the study was to assess sputum total IgE and cytokines in asthmatics according to sputum cellular phenotype.MethodsWe studied 122 subjects including 22 non atopic healthy subjects, 41 eosinophilic (sputum eosinophils ≥3%), 16 neutrophilic (sputum neutrophils >76%) and 43 pauci-granulocytic asthmatics (sputum eosinophils <3% and sputum neutrophils ≤76%) recruited from the asthma clinic at CHU Liege.Sputum supernatant total IgE (tIgE) was measured by ImmunoCAP and sputum supernatant cytokines (IL-4, IL-5, IL-6, IL-10, IL-13, IL-17, IFN-γ and TNF-α) were measured with the Luminex xMAP Technology by using commercially available Fluorokine MAP kits.ResultsAfter concentrating sputum samples, total IgE was detectable in the majority of subjects. Sputum IgE was raised in asthmatics when compared to healthy subjects. Overall, asthmatics did not significantly differ from healthy subjects with respect to cytokine levels. The eosinophilic asthma phenotype, however, was characterised by raised sputum tIgE, IL-5 and IL-13 compared to healthy subjects (p<0.001, p<0.001 and p<0.05 respectively) and pauci-granulocytic asthma (p<0.01, p<0.001 and p<0.05 respectively) and raised IL-5 compared to neutrophilic asthma (p<0.01). When patients were classified according to sputum IgE levels, it appeared that IL-5, IL-6, IL-17 and TNF-α sputum supernatant levels were raised in the “IgE high” asthmatics (IgE ≥0.1 kU/l) when compared to “IgE low” asthmatics (IgE<0.1 kU/l).ConclusionThe eosinophilic asthma phenotype was associated with raised sputum IgE and a Th2 cytokine profile. Raised sputum IgE was associated with a heterogeneous cytokine overproduction.
Highlights
It is recognised that asthma comprises several inflammatory phenotypes and Simpson has proposed to break down asthma according to the granulocyte fraction contained in sputum cells [1]
Exhaled nitric oxide (FeNO50) was higher in eosinophilic asthmatics compared to healthy subjects (p,0.05) and pauci-granulocytic asthmatics (p,0.001)
Our study shows that eosinophilic asthmatics have higher total IgE concentrations in the sputum as compared to paucigranulocytic asthmatics and healthy subjects
Summary
It is recognised that asthma comprises several inflammatory phenotypes and Simpson has proposed to break down asthma according to the granulocyte fraction contained in sputum cells [1]. Several studies showed that a fraction of asthmatic patients who exhibited the clinical symptoms of asthma and airway hyperresponsiveness do not have raised sputum eosinophils [3] and that this non-eosinophilic pattern of inflammation occurs across the all spectrum of severity [4,5,6]. A fraction of non-eosinophilic asthmatics exhibit raised airway neutrophilic inflammation. Those patients with non-eosinophilic asthma appear to be relatively resistant to corticosteroid therapy and are likely to recognize different underlying molecular mechanisms [7]. Local IgE production may play a role in asthma pathogenesis. The aim of the study was to assess sputum total IgE and cytokines in asthmatics according to sputum cellular phenotype
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