Although eosinophils are one of the least abundant subpopulations of cells in blood circulation, they circumvent this low number by the highly potent content of their granules. Their involvement in a broad spectrum of pathological conditions such as acute and chronic infections, cancer, and thrombosis makes them an interesting research topic for the scientific community. Eosinophils play critical roles in the maintenance of immune homeostasis by their effector and modulatory functions in shaping innate and adaptive responses. Although they are mainly investigated for their roles in parasitic infections, there is a growing body of evidence that eosinophils play roles in fungal, bacterial, and viral infections as wells as tissue repair and they might be in the centre of key signalling pathways encompassing Th2 cells, B cells, and mast cells. Eosinophil-associated diseases (EADs) are rare and heterogeneous. Immune system-related pathology in EADs is characterized by the presence of eosinophils in tissues and/or peripheral blood.

Due to EAD’s heterogeneity, the complexity of tissue involvement, a limited number of animal models as well as their low numbers in blood, technical challenges in working with eosinophils, and insufficiency of standardized methods in histopathology hinder the progress of basic eosinophil research. Furthermore, clinical trials and drug development studies on rare EADs are limited. Further research needs to be done in terms of understanding eosinophil phenotyping based on gene profiling and the role of eosinophil subsets in tissues in the intestine, respiratory tract and oesophagus. Moreover, further research needs to be conducted to improve our understanding of how to determine biomarkers of eosinophil activation, (de)granulation and tissue load and the role of eosinophils in human diseases. Therefore, the design of new drugs targeting eosinophils to selectively eradicate the eosinophils and better treatment approaches to address the unmet need for EAD diseases should be prioritized.

The goal of this Special Issue is to bring together original research and review articles aiming to improve our understanding of eosinophil-associated diseases (EADs). We welcome basic eosinophil immunobiology and translational medicine studies. We encourage submissions that include data from in vivo disease models, in vitro cell culture models and in silico studies. We hope that this Special Issue highlights unaddressed research in eosinophils and contributes to new experimental or analytical approaches. We also hope that this Special Issue serves as a valuable reference source for researchers who are interested in eosinophils, such as immunologists, microbiologists, molecular biologists, clinicians as well as bioinformaticians.

Potential topics include but are not limited to the following:

• Eosinophils cells in asthma and allergy
• Eosinophils cells in cancer
• Eosinophils cells in the maintenance of homeostasis and development
• Eosinophils cells in health and disease (e.g. cardiovascular diseases, obesity, etc.)
• Eosinophils cells under hypoxic conditions
• Eosinophils in oxidative stress and autophagy
• Eosinophils in autoimmunity
• Innate immune response regulation by eosinophils
• Adaptive immune response regulation by eosinophils
• Regulation of inflammation and pattern recognition receptors (toll-like receptors (TLRs), nucleotide-binding domain and leucine-rich repeat-containing receptors (NLRs), C type lectin receptor and retinoic acid-inducible gene I (RIG-I)-like receptors) in eosinophils
• Eosinophil and immunological memory
• Eosinophilic signalling networks
• In silico modelling studies focusing on eosinophilic protein interactions
• Gene and/or protein expression profiling of eosinophils