Functions of tissue-resident eosinophils

Abstract

Eosinophils are a prominent cell type in particular host responses such as the response to helminth infection and allergic disease. Their effector functions have been attributed to their capacity to release cationic proteins stored in cytoplasmic granules by degranulation. However, eosinophils are now being recognized for more varied functions in previously underappreciated diverse tissue sites, based on the ability of eosinophils to release cytokines (often preformed) that mediate a broad range of activities into the local environment. In this Review, we consider evolving insights into the tissue distribution of eosinophils and their functional immunobiology, which enable eosinophils to secrete in a selective manner cytokines and other mediators that have diverse, ‘non-effector’ functions in health and disease.

Contemporary understanding of the secretory granules in human eosinophils

“…Eosinophils are remarkable secretory cells able to release a large and varied collection of immune mediators, including cationic proteins, cytokines, chemokines, and growth factors, which underlie eosinophil functions during inflammatory, allergic, and immunoregulatory situations (reviewed in Refs. ). How these mediators exit the cell is still not well understood.…”

Frontline Science: Cytokine-mediated developmental phenotype of mouse eosinophils: IL-5-associated expression of the Ly6G/Gr1 surface Ag

“…Eosinophils are granulocytic leukocytes that develop in the bone marrow from pluripotential progenitor cells . While much of the older literature on eosinophils focuses on their role as cytotoxic effector cells, this limited view has been largely supplanted by findings that have revealed their broad and extensive immunomodulatory potential . Recent studies that explore the role of eosinophils at homeostasis in the gastrointestinal tract, that examine their distinct eosinophil‐mediated antimicrobial activities and that define the properties of eosinophil‐specific subtypes, all suggest that there are new and profound complexities remaining to be resolved.…”

Follicular helper T cells recruit eosinophils into host liver by producing CXCL12 during Schistosoma japonicum infection

“…More importantly, eosinophils have been shown to be an important in vivo source of IL‐4 to maintain the Th2 response to schistosome infection, which is central to the development of hepatic granuloma and fibrosis . In addition, eosinophils also contribute to CD4 + T cell responses by producing chemokines such as CCL17, CCL22, CXCL9 and CXCL10, which orchestrates the schistosoma granuloma formation . Thus, studying the mechanisms underlying the recruitment of eosinophils into the liver provides additional insights into granuloma formation and novel strategies for schistosomiasis treatment.…”