IL-9-producing CD4⁺ T cells have been considered to represent a distinct T helper cell (T_H cell) subset owing to their unique developmental programme in vitro, their expression of distinct transcription factors (including PU.1) and their copious production of IL-9. It remains debatable whether these cells represent a truly unique T_H cell subset in vivo, but they are closely related to the T helper 2 (T_H2) cells that are detected in allergic diseases. In recent years, increasing evidence has also indicated that IL-9-producing T cells may have potent abilities in eradicating advanced tumours, particularly melanomas. Here, we review the latest literature on the development of IL-9-producing T cells and their functions in disease settings, with a particular focus on allergy and cancer. We also discuss recent ideas concerning the therapeutic targeting of these cells in patients with chronic allergic diseases and their potential use in cancer immunotherapy.

由于其独特的体外发育程序、不同转录因子（包括 PU.1）的表达及其大量生产，产生 IL-9 的 CD4 ⁺ T 细胞被认为是一种独特的 T 辅助细胞（T _H细胞）亚群IL-9。这些细胞是否代表体内真正独特的 T _H细胞亚群仍然存在争议，但它们与 T 辅助细胞 2（T _H2) 在过敏性疾病中检测到的细胞。近年来，越来越多的证据表明，产生 IL-9 的 T 细胞可能具有根除晚期肿瘤，尤其是黑色素瘤的强大能力。在这里，我们回顾了关于产生 IL-9 的 T 细胞的发展及其在疾病环境中的功能的最新文献，特别关注过敏和癌症。我们还讨论了关于这些细胞在慢性过敏性疾病患者中的治疗靶向及其在癌症免疫治疗中的潜在用途的最新想法。