Low Dose IL-2 Therapy in Patients With a Depressive Episode in the Course of a Bipolar Disorder

Inclusion Criteria: * A depressive episode according to DSM-V criteria in the course of a bipolar disorder * MADRS score \> 17 * Already on a mood stabilizer and/or antidepressant * Patient with a normal or controlled thyroid function * Male or female both using effective methods of contraception during treatment if sexually active. Exclusion Criteria: * \- Contraindication to IL-101 therapy: * Hypersensitivity to active substance or excipient; * Active infection requiring antibiotics therapy; * Organ failure (e.g., liver, kidney, lung and heart); * Immunosuppressed patient * Hepatotoxic, nephrotoxic, myelotoxic or cardiotoxic drugs * Other chronic diseases * Signs of active infection requiring treatment * Previous history of organ transplantation * Leukocytes \< 4000 / mm3, platelets \< 100 000 / mm3, Hemoglobin \< 10.0 g/dL or 6.2 mmol/L, red cell blood \< 3.5 T/L. * Anti-TPO or anti-TG or anti-TRACKS positive at inclusion. * Use of anti-inflammatory medication on a regular basis for a chronic inflammatory/autoimmune Disorder (NSAD, immunosuppressant IV-Ig based treatment); * Ongoing fever \< 38 * uncontrolled diabetes type I or II; * Existing cancer or history of cancer in the last 5 years (except skin epidermoid cancer or in-situ cervix cancer); * Existing or planned pregnancy or lactation; * Person under legal protection (1121-8 of CSP, Public Health Code * Pregnant and parturient and Breast feeding women (1121-5 of CSP) * legally detained person (1121-6 of CSP) * hospitalisation without consent * under the age of majority (1121-7of CSP) * Immediate risk for suicidal behaviour (MADRS-item 10 \>2 or columbia \> 2 for suicide idea); * Known HIV infection or clinically manifest Acquired Immune Deficiency Syndrome (AIDS), Parkinson's or Alzheimer's disease, or any other serious condition likely to interfere with the conduct of the trial; * Participation to an interventional study concomitantly or within 30 days prior to this study, except in the cohorts studies aiming at the analysis of immuno-inflammatory biomarkers and/or brain imaging studies. * Patients thought to be unreliable or incapable of complying with the requirements of the protocol; * Patient is relative of, or staff directly reporting to the investigator; * Patient is employee of the sponsor.