Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, MBRB2074, MC669, 900 S. Ashland Ave, Chicago, IL 60607, United States.
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, 2015 SW 16th Ave, Gainesville, FL 32610, United States.
J Leukoc Biol. 2024 Jul 25;116(2):247-259. doi: 10.1093/jleuko/qiae109.
The origins and evolution of the eosinophilic leukocyte have received only scattered attention since Paul Ehrlich first named this granulocyte. Studies suggest that myeloperoxidase, expressed by granulocytes, and eosinophil peroxidase diverged some 60 to 70 million years ago, but invertebrate to vertebrate evolution of the eosinophil lineage is unknown. Vertebrate eosinophils have been characterized extensively in representative species at light microscopic, ultrastructural, genetic, and biochemical levels. Understanding of eosinophil function continues to expand and includes to date regulation of "Local Immunity And/Or Remodeling/Repair" (the so-called LIAR hypothesis), modulation of innate and adaptive immune responses, maintenance of tissue and metabolic homeostasis, and, under pathologic conditions, inducers of tissue damage, repair, remodeling, and fibrosis. This contrasts with their classically considered primary roles in host defense against parasites and other pathogens, as well as involvement in T-helper 2 inflammatory and immune responses. The eosinophils' early appearance during evolution and continued retention within the innate immune system across taxa illustrate their importance during evolutionary biology. However, successful pregnancies in eosinophil-depleted humans/primates treated with biologics, host immune responses to parasites in eosinophil-deficient mice, and the absence of significant developmental or functional abnormalities in eosinophil-deficient mouse strains under laboratory conditions raise questions of the continuing selective advantages of the eosinophil lineage in mammals and humans. The objectives of this review are to provide an overview on evolutionary origins of eosinophils across the animal kingdom, discuss some of their main functions in the context of potential evolutionary relevance, and highlight the need for further research on eosinophil functions and functional evolution.
嗜酸性粒细胞的起源和进化自保罗·埃尔利希（Paul Ehrlich）首次命名这种粒细胞以来，仅受到了零散的关注。研究表明，粒细胞表达的髓过氧化物酶和嗜酸性粒细胞过氧化物酶在大约 6000 万至 7000 万年前就已经分化，但嗜酸性粒细胞在无脊椎动物到脊椎动物的进化过程中尚不清楚。在代表物种中，已经从光镜、超微结构、遗传和生化水平广泛研究了脊椎动物嗜酸性粒细胞。对嗜酸性粒细胞功能的理解仍在不断扩展，包括迄今为止对“局部免疫和/或重塑/修复”（所谓的 LIAR 假说）的调节、调节先天和适应性免疫反应、维持组织和代谢内稳态以及在病理条件下诱导组织损伤、修复、重塑和纤维化。这与它们在宿主防御寄生虫和其他病原体以及参与 Th2 炎症和免疫反应中被认为的主要作用形成对比。嗜酸性粒细胞在进化早期出现，并在整个分类群的固有免疫系统中保留下来，这说明了它们在进化生物学中的重要性。然而，用生物制剂治疗嗜酸性粒细胞耗竭的人类/灵长类动物中成功的妊娠、嗜酸性粒细胞缺陷小鼠中的寄生虫宿主免疫反应以及在实验室条件下嗜酸性粒细胞缺陷小鼠品系中没有明显的发育或功能异常，都对嗜酸性粒细胞在哺乳动物和人类中的持续选择性优势提出了质疑。本文的目的是概述整个动物界嗜酸性粒细胞的进化起源，讨论它们在潜在进化相关性中的一些主要功能，并强调需要进一步研究嗜酸性粒细胞的功能和功能进化。
