27-hydroxycholesterol causes cognitive deficits by disturbing Th17/Treg balance and the related immune responses in mild cognitive impairment patients and C57BL/6J mice.

"Declarations Ethics approval and consent to participateThe population study was conducted with the approvement of the Ethics Committee of Capital Medical University (2013SY35) and all participants have signed the informed consent before inclusion. All animal experiments were approved by the Ethics Committee of Capital Medical University (Ethics: AEEI-2014-047) and conducted in accordance with the ethical standards. Consent for publicationAll the co-authors and participants have given their consent for publication in Journal of Neuroinflammation. Competing interestsThe authors declare that they have no competing interest. Competing interests The authors declare that they have no competing interest."

"Funding This study was supported by the State Key Program of the National Natural Science Foundation of China (81330065) and the National Natural Science Foundation of China (82373557 and 82173501)."