Eosinophilic disorders encompass a large spectrum of heterogeneous diseases sharing the presence of elevated numbers of eosinophils in blood and/or tissues. Among these disorders, the role of eosinophils can vary widely, ranging from a modest participation in the disease process to the predominant perpetrator of tissue damage. In many cases, eosinophilic expansion is polyclonal, driven by enhanced production of interleukin-5, mainly by type 2 helper cells (Th2 cells) with a possible contribution of type 2 innate lymphoid cells (ILC2s). Among the key steps implicated in the establishment of type 2 immune responses, leukocyte recruitment toward inflamed tissues is particularly relevant. Herein, the contribution of the chemo-attractant molecule thymus and activation-regulated chemokine (TARC/CCL17) to type 2 immunity will be reviewed. The clinical relevance of this chemokine and its target, C-C chemokine receptor 4 (CCR4), will be illustrated in the setting of various eosinophilic disorders. Special emphasis will be put on the potential diagnostic, prognostic, and therapeutic implications related to activation of the TARC/CCL17-CCR4 axis.

嗜酸性粒细胞疾病包括大范围的异质性疾病，它们共享血液和/或组织中嗜酸性粒细胞数量升高的存在。在这些疾病中，嗜酸性粒细胞的作用差异很大，从对疾病过程的适度参与到组织损伤的主要肇事者。在许多情况下，嗜酸性粒细胞扩增是多克隆的，主要由 2 型辅助细胞（Th2 细胞）和 2 型先天淋巴细胞 (ILC2s) 的增加产生的白细胞介素 5 驱动。在与建立 2 型免疫反应有关的关键步骤中，白细胞向发炎组织的募集尤为重要。本文将综述化学引诱分子胸腺和活化调节趋化因子 (TARC/CCL17) 对 2 型免疫的贡献。这种趋化因子及其靶点 CC 趋化因子受体 4 (CCR4) 的临床相关性将在各种嗜酸性粒细胞疾病的环境中得到说明。将特别强调与 TARC/CCL17-CCR4 轴激活相关的潜在诊断、预后和治疗意义。