Neutrophil eosinophil basophil
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Roles and Mechanisms of Neutrophils, Eosinophils, and Basophils in Inflammation
Introduction to Granulocytes: Neutrophils, Eosinophils, and Basophils
Neutrophils, eosinophils, and basophils are critical components of the immune system, collectively known as granulocytes. These cells are essential in both microbe-induced and sterile inflammation, playing distinct roles in immune responses and inflammation regulation 1. Understanding the unique functions and mechanisms of these granulocytes is crucial for developing targeted therapies for various inflammatory conditions.
Granulocyte Lifespan and Inflammation Regulation
The lifespan of granulocytes is a key factor in controlling the severity of inflammatory responses. Recent research has highlighted the molecular mechanisms that regulate the cell death and survival of neutrophils, eosinophils, and basophils. Dysregulation of these pathways can lead to inflammation-associated immunopathology, suggesting that targeting granulocyte lifespan could be a promising therapeutic strategy 1.
Adhesion Mechanisms in Inflammation
Cytokines such as interleukin 1 (IL-1) enhance the adhesiveness of endothelial cells for granulocytes, facilitating their recruitment to inflammation sites. IL-1 induces the expression of adhesion molecules like ICAM-1, ELAM-1, and VCAM-1, which play distinct roles in the adhesion of neutrophils, eosinophils, and basophils. Notably, VCAM-1 is particularly important for eosinophil and basophil adhesion, highlighting a mechanism for their selective recruitment during inflammation 2.
Bioelectrical Properties and Granulocyte Classification
Granulocytes can be differentiated based on their inherent single-cell bioelectrical properties, such as diameter, specific membrane capacitance, and cytoplasmic conductivity. These parameters allow for the classification of neutrophils, eosinophils, and basophils, although distinguishing between eosinophils and basophils remains challenging 3.
Functional Heterogeneity of Basophils
Basophils, although the rarest granulocytes, exhibit significant functional heterogeneity. Mass cytometry has identified four distinct subpopulations of basophils, each with unique phenotypic and functional characteristics. These subpopulations may play different roles in immune responses, particularly in non-IgE-mediated immunity 4.
Eosinophil-Specific Characteristics
Eosinophils are characterized by their affinity for acid aniline dyes and the presence of eosinophil-specific proteins in their cytoplasmic granules. Despite the lack of unique cell-surface proteins, eosinophils can be identified and enumerated based on their tinctorial properties. Eosinophilia, or increased eosinophil production, is associated with various diseases 5.
Chemotactic Responses to C3a and C5a
The chemotactic responses of granulocytes to complement components C3a and C5a differ significantly. While C3a directly activates eosinophils, it does not activate neutrophils. Instead, neutrophil activation by C3a is secondary to eosinophil activation, indicating a complex interplay between these granulocytes in inflammatory responses 6.
Diagnostic Indicators in Systemic Amyloidosis
The neutrophil-to-lymphocyte ratio (NLR) and eosinophil-to-basophil ratio (EBR) are valuable diagnostic indicators for systemic amyloidosis. Elevated NLR and EBR, along with decreased mean platelet volume (MPV), are associated with this condition, demonstrating the diagnostic potential of these hematological parameters 7.
Toll-Like Receptor Expression and LPS Responses
Neutrophils express Toll-like receptors (TLRs) and respond to lipopolysaccharide (LPS), whereas eosinophils and basophils do not. Neutrophil responses to LPS are heavily dependent on the presence of monocytes, suggesting that monocytes play a crucial role in orchestrating leukocyte responses to LPS 8.
Neutrophil Granule Protein Processing and Secretion
Neutrophils are equipped with granules containing pre-formed pro-inflammatory mediators, which are rapidly released upon activation. This ability to store and secrete mediators without the need for new synthesis is vital for their role in rapid immune responses 9.
Conclusion
Neutrophils, eosinophils, and basophils are integral to the immune system's response to inflammation. Their unique properties, adhesion mechanisms, and functional heterogeneity underscore their importance in both health and disease. Continued research into the regulation and function of these granulocytes holds promise for developing targeted therapies for inflammatory conditions.
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Living and dying for inflammation: neutrophils, eosinophils, basophils.
Targeting granulocyte lifespan could be therapeutically promising, as dysregulation of death pathways in granulocytes contributes to inflammation-associated immunopathology.
Highly CitedAdhesion of human basophils, eosinophils, and neutrophils to interleukin 1-activated human vascular endothelial cells: contributions of endothelial cell adhesion molecules
ICAM-1, ELAM-1, and VCAM-1 play distinct roles in the adhesion of human basophils, eosinophils, and neutrophils to interleukin 1-activated vascular endothelial cells, suggesting a novel mechanism for inflammation recruitment.
In Vitro StudyHighly CitedInherent single‐cell bioelectrical parameters of thousands of neutrophils, eosinophils and basophils derived from impedance flow cytometry
Inherent single-cell bioelectrical parameters can effectively classify neutrophils from eosinophils or basophils, but not effectively distinguish eosinophils from basophils.
In Vitro StudyMass Cytometry Phenotyping of Human Granulocytes Reveals Novel Basophil Functional Heterogeneity
Four distinct subpopulations of human basophilic granulocytes have been identified, offering insights into their heterogeneity and potential roles in non-IgE-mediated immunity.
In Vitro StudyC3a is a chemotaxin for human eosinophils but not for neutrophils. I. C3a stimulation of neutrophils is secondary to eosinophil activation
C3a directly activates human eosinophils, while it fails to activate neutrophils, and its indirect stimulation of neutrophils may be due to eosinophil contamination in neutrophil preparations.
In Vitro StudyHighly CitedToll-Like Receptor (TLR)2 and TLR4 in Human Peripheral Blood Granulocytes: A Critical Role for Monocytes in Leukocyte Lipopolysaccharide Responses1
Monocytes play a critical role in leukocyte lipopolysaccharide responses, with neutrophils playing a lesser role and eosinophils and basophils not playing a significant role in peripheral blood function.
In Vitro StudyHighly CitedGranule Protein Processing and Regulated Secretion in Neutrophils
Neutrophils play a crucial role in innate immunity by synthesizing and storing pre-formed pro-inflammatory mediators, and regulating their release through regulated exocytosis.
Highly CitedGranules of the human neutrophilic polymorphonuclear leukocyte.
POLYMORPHONUCLEAR leukocytes were discovered by Paul Ehrlich,[1][1] when fixation and staining techniques made it possible to identify the lobulated nucleus and the granules that have given name to these cells and allowed for their classification as eosinophils, basophils, and neutrophils.
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