Exploring the Diversity and Emerging Powers of Eosinophil Subpopulations

Eosinophils, once viewed as terminal effector cells of type 2 immunity, are now recognized as a heterogeneous population with context-dependent plasticity and diverse roles in tissue homeostasis, immune regulation, and disease. Emerging data from transcriptomic and functional studies, particularly in murine models, have identified distinct eosinophil subsets shaped by local environmental cues and systemic signals. These include regulatory and pro-inflammatory subsets in the gastrointestinal tract, lung, adipose tissue, synovium, and more, each defined by unique phenotypic and transcriptional signatures. In humans, eosinophil heterogeneity is increasingly evident in asthma, nasal polyposis, and eosinophilic esophagitis, although less well characterized than in mice. This review synthesizes recent advances that redefine eosinophil biology, emphasizing their functional diversity and context-dependent specialization across tissues and disease states, and how these subsets are regulated by anti-IL-5 therapies.