Eosinophils are a minor subset of the granulocyte lineage distinguished by their unique morphology, phenotype, cytoplasmic contents, and function. Evolutionarily, these are ancient cells whose existence has been conserved within vertebrates for millions of years, suggesting that their contribution to innate immunity and other pathologic and homeostatic responses are important to the host. Knowledge regarding the role of eosinophils in health and disease took a leap forward in 2004 with the creation of mouse strains deficient in eosinophils. This advance was paralleled in humans using pharmacology, namely, with the development of drugs capable of selectively reducing and sometimes even eliminating human eosinophils in those receiving these agents. As a result, a more definitive picture of what eosinophils do, and do not do, is emerging. This review will summarize recent advances in our understanding of the role of eosinophils in human disease by focusing mainly on data from clinical studies with anti-eosinophil therapies, even though the first of such agents, mepolizumab, was only approved in the USA in November 2015. Information regarding both efficacy and safety will be highlighted, and where relevant, intriguing data from animal models will also be mentioned, especially if there are conflicting effects seen in humans.

嗜酸性粒细胞是粒细胞谱系的一个小子集，以其独特的形态、表型、细胞质内容物和功能而著称。从进化上讲，这些是古老的细胞，它们在脊椎动物中的存在已经保存了数百万年，这表明它们对先天免疫和其他病理和稳态反应的贡献对宿主很重要。2004 年，随着嗜酸性粒细胞缺乏的小鼠品系的出现，有关嗜酸性粒细胞在健康和疾病中的作用的知识有了飞跃。这一进步与使用药理学的人类平行，即开发能够选择性地减少甚至有时甚至消除接受这些药物的人中的人类嗜酸性粒细胞的药物。因此，正在出现关于嗜酸性粒细胞做什么和不做什么的更明确的图景。