Abstract
Eosinophils have traditionally been viewed as pathological effector cells primarily involved in antiparasitic and allergic immune reactions; however, it is becoming increasingly apparent that eosinophils are multifaceted leukocytes that contribute to a variety of roles in both health and disease. Recent research shows that eosinophils play important immunoregulatory roles across various tissue sites including the gastrointestinal tract, adipose tissue, lung, liver, heart, muscles, thymus and bone marrow. With recent advances in our knowledge and appreciation of eosinophil immunoregulatory functions at these tissue sites, as well as emerging research demonstrating the existence of distinct subsets of eosinophils, a review of this topic is timely. Although some questions remain regarding eosinophil function and heterogeneity, this review summarizes the contemporary understanding of the immunoregulatory roles of eosinophils across various tissues and discusses the latest research on eosinophil heterogeneity and subsets.