APOE and Alzheimer disease: The main findings of this study were as follows: (1) most of healthy controls did not have detectable levels of peripheral IL-33; (2) the IL-33 expression showed positive linear trend between healthy controls, aMCI, and AD; (3) the IL-33-expressing patients preserved their cognitive function over 1-year period; (4) the cognitive preservation was not associated with the levels of Aβ and tau and the expression of ApoE ε4; and (5) the aMCI patients with subsequent AD conversion had higher proportion of IL-33 non-expression.