Prognostic significance of plasma IL-2 and sIL-2Rα in patients with first-ever ischaemic stroke

Background: An imbalance between circulating neuroprotective and neurotoxic T cell subsets leads to poor prognosis in acute ischaemic stroke (AIS). Preclinical studies have indicated that the soluble form of the interleukin-2 receptor alpha (sIL-2R alpha)-IL-2 complex regulates T cell differentiation. However, the association between sIL-2R alpha levels and AIS remains unclear. Methods: A total of 201 first-ever AIS patients within 24 h after stroke onset and 76 control subjects were recruited. The National Institutes of Health Stroke Scale (NIHSS) score and 3-month functional outcome (modified Rankin Scale [mRS] score) at admission were assessed. Plasma sIL-2R alpha and IL-2 levels at admission were measured. Prognostic significance was identified by using univariate and multivariate logistic regression analyses. Results: Patients with poor functional outcomes at 3 months had significantly higher levels of sIL-2R alpha and lower levels of IL-2 than patients with good outcomes. Moreover, sIL-2R alpha levels showed a strong positive correlation with NIHSS and mRS scores (p< 0.0001), whereas IL-2 levels were negatively correlated with mRS scores (p< 0.01). Univariate analyses showed that higher sIL-2R alpha and IL-2 levels were associated with an increased and reduced risk of unfavourable outcomes, respectively. After adjusting for confounding variables, the sIL-2R alpha level remained independently associated with an increased risk of an unfavourable outcome, and adding sIL-2R alpha levels to the conventional risk factor model significantly improved risk reclassification (net reclassification improvement 17.56%,p= 0.003; integrated discrimination improvement 5.78%,p =0.0003). Conclusions: sIL-2R alpha levels represent a novel, independent prognostic marker that can improve the currently used risk stratification of AIS patients. Our findings also highlight that elevated plasma sIL-2R alpha and IL-2 levels manifested opposite correlations with functional outcome, underlining the importance of IL-2/IL-2R autocrine loops in AIS.