Identification of eosinophils in whole blood samples by flow cytometry is often problematic. There are usually only a low number and percentage of cells that may be detected, and it may be difficult to discriminate eosinophils from other granulocytes. Here, we propose a simple approach using the eosinophil's intrinsic autofluorescence properties, combined with detection of CCR3 expression, to reliably identify eosinophils in a mixed leukocyte population.
Eosinophils are often predominant inflammatory leukocytes infiltrating oral squamous carcinoma (OSC) sites. Prostaglandins are secreted by oral carcinomas and may be involved in eosinophil infiltration. The objective of this study was to determine the factors contributing to eosinophil migration and potential anti-neoplastic effects on OSC. Eosinophil degranulation was evaluated by measuring release of eosinophil peroxidase (EPO). Eosinophil chemotaxis towards OSC cells was assessed using artificial basement membrane. Eosinophil infiltration was prominent within the tissue surrounding the OSC tumor mass. We observed growth inhibition of the OSC cell line, SCC-9, during co-culture with human eosinophils, in vitro, which correlated with EPO activity that possesses growth inhibitory activity. The PGD2 synthase inhibitor, HQL-79, abrogated migration towards SCC-9. Our data suggest that OSC-derived PGD2 may play an important role via CRTH2 (the PGD2 receptor on eosinophils) in eosinophil recruitment and subsequent anti-tumor activity through the action of eosinophil cationic proteins.
Background: Asthma severity and eosinophilia correlate with a deficiency in vitamin D and its active metabolite calcitriol. Calcitriol modulates numerous leukocyte functions, but its effect on eosinophils is not fully understood. We postulated that calcitriol exerts a direct effect on eosinophil biology by modulating cell survival. Methods: Purified peripheral blood eosinophils from atopic donors were incubated in the presence of calcitriol for up to 14 days with or without IL-5. The effect of calcitriol on eosinophil viability was measured using the annexin-V/propidium iodide flow cytometry assay. We also examined the release of eosinophil peroxidase (EPX) in media using a flow cytometry assay with anti-EPX antibodies, and the enzymatic activity of EPX was measured by an OPD-based colorimetric assay. Results: We observed that calcitriol sustained cell viability in eosinophils with a concurrent reduction of necrotic cells. This effect was amplified by the addition of IL-5. In parallel, we observed that a physiological dose of calcitriol (10 nM) significantly reduced eosinophil necrosis and cytolytic release of EPX in media when coincubated with IL-5. Conclusion: These results suggest that calcitriol may exert a direct effect on eosinophils by reducing necrosis and the cytolytic release of inflammatory mediators like EPX.
Introduction Eosinophils are continually targeted in allergic airway inflammatory disease therapies. The presence of their granules in airway tissues remains unexplained, yet implies the involvement of necrosis. The latter's definition has evolved into a highly regulated and distinct signalling pathway leading to physiological inflammation, known as necroptosis. Even though necroptosis is a recently introduced concept, we currently recognize its role as an alternative mechanism in the absence of apoptosis. Furthermore, necroptosis seems to act as a host-defence strategy against viral infections, which consequently associates itself with eosinophils' role in airway viral clearance. The aim of this review is to discuss if necroptosis of eosinophils is involved in allergic airway inflammation. Conclusion The investigation of necroptosis in eosinophil is currently an area which lacks research, yet harbours great promise for drug development.
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