Inclusion Criteria:
* Patients aged \> 18
* Age of disease onset \< 70 years
* Clinical and biological diagnosis of AD based on
* Progressive amnestic syndrome associated or not with other cognitive impairments
* Biological criteria: CSF biomarkers suggestive of AD.
* Brain MRI congruent with the diagnosis, left to the appreciation of the investigator
* CDR (Clinical Dementia Rating Scale) = 0.5 or 1
* If patients have an antidepressant or acetylcholinesterase inhibitors treatment, patients must be treated with stable doses of treatment for at least 1 month before inclusion.
* Have a caregiver who provides a separate written informed consent to participate. If a caregiver/study informant cannot continue, one replacement is allowed.
* Have adequate vision and hearing for neuropsychological testing in the opinion of the investigator.
* Have given written informed consent approved by the ethical review board (ERB) governing the site.
* The patient has to have a French social security number and be fluent and literate in French.
Exclusion Criteria:
* Subject with a psychiatric evolutionary and/or badly checked.
* Subject with a grave, severe or unstable pathology (left to the judgement of the investigator) the nature of which can interfere with the variables of evaluation.
* Epileptic subjects
* Subject under guardianship or curatorship
* Subject presenting contraindications to the MRI
* Known or supposed history (\< or = 5 years) of severe alcoholism or misuse of drugs
* Vascular, inflammatory or expansive, visible lesion in the MRI, which can interfere on the criteria of diagnosis.
* No health insurance
* Women of childbearing potential: a woman is considered of childbearing potential (WOCBP), i.e. fertile, following menarche and until becoming post-menopausal unless permanently sterile. Permanent sterilisation methods include hysterectomy, bilateral salpingectomy and bilateral oophorectomy. A postmenopausal state is defined as no menses for 12 months without an alternative medical cause.
* History of auto-immune disease
* History within the past 10 years of a primary or recurrent malignant disease
* Diagnosis or history of other possible etiology of dementia, including but not limited to other neurodegenerative disorders (FTD, LBD, VaD, HD, PD, PSP-CBD).
* Renal dysfunction at inclusion, clearance \<30 mL/min
* Chronic hepatic diseases as indicated by liver function tests abnormalities
* Abnormal thyroid function
* Therapeutic trial within 1 year preceding the first study period, or participation in a trial with active or passive immunization against amyloid if patient was assigned to the active treatment arm.
* Clinically significant evidence of Active viral infection (CMV, EBV, HCV, HBV, TPHA-VDRL, HIV)
* Current or medical history of severe cardiopathy,
* \- Severe dysfunction in a vital organ
* Patients with White Blood Count (WBC) \< 4.000/mm3; platelets \< 100.000/mm3; hematocrit (HCT) \< 30%.
* Patients with serum bilirubin and creatinine outside normal range.
* Patients with organ allografts.
* Patients who are likely to require corticosteroids
