The interleukin (IL)-2 – IL-2 receptor (IL-2R) pathway is important in immunity, but is also involved in maintenance of self-tolerance. This paradox is further complicated by shedding of the IL-2Rα chain, revealing soluble (s)IL-2R. Binding of IL-2 to sIL-2R may either reduce or enhance responses depending on the target cell being involved in immunity or self-tolerance. Since sIL-2R levels are increasingly measured in clinical practice, it is detrimental for clinical interpretation to understand the possible functional impact of IL-2R shedding. In this review the role of the IL-2 – IL-2R pathway is explored and the conflicting results on the function of sIL-2R are summarized. Finally, the added value of measuring sIL-2R in different types of diseases is being elaborated upon in terms of diagnosis, follow-up, and prognosis. Adequate interpretation of results is hampered by the apparent gap in our knowledge about the functional role of sIL-2R in immunity and tolerance.

白介素（IL）-2 – IL-2受体（IL-2R）途径在免疫中很重要，但也与维持自身耐受性有关。IL-2Rα链脱落，使可疑的IL-2R暴露，使这一矛盾进一步复杂化。IL-2与sIL-2R的结合可能会降低或增强反应，具体取决于参与免疫或自我耐受的靶细胞。由于sIL-2R水平在临床实践中越来越多地被测量，因此对临床解释了解IL-2R脱落可能的功能影响是有害的。在这篇综述中，探讨了IL-2 – IL-2R途径的作用，并总结了关于sIL-2R功能的矛盾结果。最后，从诊断，随访和预后方面详细阐述了在不同类型疾病中测量sIL-2R的附加价值。