The circulating levels of IL-33 are in general very low, with only a limited increase in AD (3.5 ± 11.3 pg/ml) that, however, reaches statistical significance in comparison with NHS (0.85 ± 2.2 pg/ml, p = 0.006), SMC (0.40 ± 1.05, p = 0.043), and MCI (0.60 ± 0.91, p = 0.014) (Fig. 3, upper panel). Here, IL33 is linked to Alzheimer disease.