Role of Eosinophil Granulocytes in Allergic Airway Inflammation Endotypes

Abstract

Eosinophil granulocytes are intriguing members of the innate immunity system that have been considered important defenders during parasitic diseases as well as culprits during allergy-associated inflammatory diseases. Novel studies have, however, found new homoeostasis-maintaining roles for the cell. Recent clinical trials blocking different Th2 cytokines have uncovered that asthma is heterogeneous entity and forms different characteristic endotypes. Although eosinophils are present in allergic asthma with early onset, the cells may not be essential for the pathology. The cells are, however, likely disease causing in asthma with a late onset, which is often associated with chronic rhinosinusitis. Assessment of eosinophilia, fraction exhaled nitric oxide (FeNO) and periostin are markers that have emerged useful in assessing and monitoring asthma severity and endotype. Current scientific knowledge suggests that eosinophils are recruited by the inflammatory environment, activated by the innate interleukin (IL)-33 and prevented from apoptosis by both lymphocytes and innate immune cells such as type two innate immune cells. Eosinophils contain four specific granule proteins that exhibit an array of toxic and immune-modulatory activates. The granule proteins can be released by different mechanisms. Additionally, eosinophils contain a number of inflammatory cytokines and lipid mediators as well as radical oxygen species that might contribute to the disease both by the recruitment of other cells and the direct damage to supporting cells, leading to exacerbations and tissue fibrosis. This review aimed to outline current knowledge how eosinophils are recruited, activated and mediate damage to tissues and therapies used to control the cells.

Atopy in chronic rhinosinusitis: impact on quality of life outcomes

“…Although there was a limited effect of atopy on CRS overall QoL, the presence of nasal polyps provided a more appreciable effect on patient symptoms. CRSwNP has been previously associated with poorer outcomes and decreased QoL . On further analysis of the CRSwNP population, there was no significant association between atopy and QoL measures.…”

The recent advances of phenotypes in acute exacerbations of COPD

“…Some studies have reported that patients with high FeNO levels will have a good response to corticosteroids and greater improvement in FEV 1 39,40. The reason for this result may be due to the fact that the FeNO level correlated well with the eosinophils, which is a good predictor for the response to corticosteroids 41,42. Antus et al43 pointed out that the optimum cutoff point for FENO as a predictor for significant increase in FEV 1 was 26.8 ppb (sensitivity: 74% and specificity: 75%).…”

Lung Pathologies in a Chronic Inflammation Mouse Model Are Independent of Eosinophil Degranulation

“…Concurrent basic research studies investigating eosinophil activities in the lungs of mouse models following allergen provocation are providing support for this hypothesis and have led us and others to suggest that pulmonary eosinophils directly modulate allergic immune responses (17)(18)(19)(20)(21)(22)(23) and contribute to the remodeling/repair processes linked with the resolution of inflammation (see References 24 and 25). These studies thus suggest that eosinophil activities likely contribute to allergic pulmonary inflammation at many levels beyond their proposed role as mediators of tissue damage and cell death through the release of eosinophil secondary granule proteins (26).…”