Abstract
Eosinophils are a minor component of circulating granulocytes, which are classically viewed as end-stage effector cells in host defense against helminth infection and promoting allergic responses. However, a growing body of evidence has emerged showing that eosinophils are versatile leukocytes acting as an orchestrator in the resolution of inflammation. Rheumatoid arthritis (RA) is the most common chronic inflammatory disease characterized by persistent synovitis that hardly resolves spontaneously. Noteworthy, a specific population of eosinophils, that is, regulatory eosinophils (rEos), was identified in the synovium of RA patients, especially in disease remission. Mechanistically, the rEos in the synovium display a unique pro-resolving signature that is distinct from their counterpart in the lung. Herein, we summarize the latest understanding of eosinophils and their emerging role in promoting the resolution of arthritis. This knowledge is crucial to the design of new approaches to rebalancing immune homeostasis in RA, considering that current therapies are centered on inhibiting pro-inflammatory cytokines and mediators rather than fostering the resolution of inflammation.
Highlights
Eosinophils are leukocytes that normally amount to less than 5% of white blood cells in the peripheral blood
During the transition from asymptomatic autoimmunity to synovial inflammation, a diverse range of pro-inflammatory cytokines produced by immune cells such as CD4+ T cells, macrophages, and fibroblast-like synoviocytes emerge quickly, which eventually contribute to cartilage damage and bone erosion in the joint [4]
Eosinophils are generated in the bone marrow from multipotent hematopoietic stem cells, which give rise to eosinophil-committed progenitors (EoPs)
Summary
Edited by: Qingjun Pan, Affiliated Hospital of Guangdong Medical University, China. Specialty section: This article was submitted to Autoimmune and Autoinflammatory Disorders, a section of the journal Frontiers in Immunology. A growing body of evidence has emerged showing that eosinophils are versatile leukocytes acting as an orchestrator in the resolution of inflammation. Rheumatoid arthritis (RA) is the most common chronic inflammatory disease characterized by persistent synovitis that hardly resolves spontaneously. The rEos in the synovium display a unique pro-resolving signature that is distinct from their counterpart in the lung. We summarize the latest understanding of eosinophils and their emerging role in promoting the resolution of arthritis. This knowledge is crucial to the design of new approaches to rebalancing immune homeostasis in RA, considering that current therapies are centered on inhibiting pro-inflammatory cytokines and mediators rather than fostering the resolution of inflammation
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