Abstract
Eosinophils are specialized white blood cells, which are involved in the pathology of diverse allergic and nonallergic inflammatory diseases. Eosinophils are traditionally known as cytotoxic effector cells but have been suggested to additionally play a role in immunomodulation and maintenance of homeostasis. The exact role of these granule-containing leukocytes in health and diseases is still a matter of debate. Degranulation is one of the key effector functions of eosinophils in response to diverse stimuli. The different degranulation patterns occurring in eosinophils (piecemeal degranulation, exocytosis and cytolysis) have been extensively studied in the last few years. However, the exact mechanism of the diverse degranulation types remains unknown and is still under investigation. In this review, we focus on recent findings and highlight the diversity of stimulation and methods used to evaluate eosinophil degranulation.
Highlights
Eosinophils are specialized white blood cells that have been traditionally perceived as cytotoxic effector cells and recently suggested to be involved in immunomodulatory and homeostatic functions [1,2]
Charcot–Leyden crystal (CLC)-/Gal-10-deficient eosinophils released significantly more eosinophil-derived neurotoxin (EDN) but not Eosinophil Peroxidase (EPX) following platelet-activating factor (PAF) stimulation [93]. These findings suggest that CLC/Gal-10 may function as a carrier for cationic ribonucleases and plays a role in the specific vesicular transport of these proteins during the piecemeal degranulation process
No significant difference in absolute level of EPX, EDN or eosinophil cationic protein (ECP) were observed in the serum of eosinophilic esophagitis (EoE) patients, while EPX and EDN serum proteins levels normalized for absolute eosinophil count (AEC) were significantly decreased [148]
Summary
Eosinophils are specialized white blood cells that have been traditionally perceived as cytotoxic effector cells and recently suggested to be involved in immunomodulatory and homeostatic functions [1,2]. Human and mouse eosinophils display differences in cell surface receptors, granule components and degranulation after activation with specific stimuli [2]. The formation of the distinct eosinophilic granules occurs at different stages of eosinophil maturation. Charcot–Leyden crystal protein (CLC, known as galectin 10) and eosinophil peroxidase (EPX, known as EPO) are found in the primary eosinophil granules [2]. In this context, it should be mentioned that primary granules were recently suggested to be early “specific” cored granules [7]. A typical constituent in leukocytes, comprise different types of proteins, growth factors, cytokines and chemokines [11]. Eotaxins are crucial for the migration of eosinophils into tissue at sites of inflammation
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