Interleukin 22 (IL-22) is known to be regulated by IL-22 binding protein (IL-22BP), a soluble, inhibitory receptor. The potential role of IL-22BP in atopic dermatitis (AD) is mostly unknown and deserves further investigation. The main objective of this study is to better understand the potential protective role of IL-22BP through the assessment of its expression at the Messenger Ribonucleic Acid (mRNA) and protein levels in skin and serum which will be correlated to the severity of the diseases and through the identification of its cellular sources in lesions. The results of this study will help to correctly interpret the levels of IL-22 in AD and will potentially allow identifying biomarkers for patient stratification and predicting clinical outcomes to targeted therapeutic agents.

This is a single-visit study. All patients will have a blood sample and 2 skin biopsies (2 mm diameter) in lesional and non lesional area

. It is planned to include 45 patients (15 patients per severity group: SCORAD ]25-50] , ]50-65]; 50-65; >65).The first 20 patients included will be group 2 and 3 patients (SCORAD > 50).

The patients will be adults with AD recruited from the cohort of patients followed up in the Dermatology department of Nantes University Hospital. A refusal rate of 4/5 is expected. Recruitment can therefore be envisaged in 18 months (2.5 patients/month). Patients will be recruited during follow-up consultations or at the first consultation in the department. Recruitment will be coordinated by the clinical research team (CRT). Blood samples will be taken by the CRT Nurse. The skin and blood samples will be sent to the CIMNA/ Immunology Laboratory Nantes University hospital

Inclusion Criteria:

• Patients with AD according to UK Working Party criteria
• Patients affiliated to French social security system
• Patients who gave written consent after reading the protocol
• Moderate to severe AD (SCORAD score>25)
• Presence of at least one lesional and one non-lesional skin area in the area covered by the clothing
• No immunosuppressive systemic treatment in progress for at least 3 months or biologics for at least 4 months

Exclusion Criteria:

• Minor patients
• Pregnant and/or breastfeeding women
• Patients under guardianship or tutorship
• Inability to understand information and instructions
• Patients undergoing systemic immunosuppressive treatment for at least 3 months or biologics for at least 4 months
• Patient included in a clinical trial
• Documented allergy to the anesthetic (xylocain)