The study aims at defining the role of soluble CD95 Ligand in the physiopathology of a rare group of inflammatory diseases: ANCA associated vasculitis. Soluble CD95 Ligand might have a prognostic and diagnostic interest as well as potential for the discovery of new therapeutic strategies.

ANCA associated vasculitis are a rare group of diseases and potentially life-threatening inflammatory conditions. There is an urgent need to describe prognostic factors and to discover new therapeutic pathways. Soluble CD95-L is a cleaved part of CD95-L which binds the CD95 Death receptor. s-CD95-L has pro-inflammatory properties for Th17 lymphocytes and Neutrophils, two cells implicated in ANCA associated vasculitis. It also plays a role in systemic lupus erythematosus (which present with the same type of renal glomerulonephritis as ANCA-associated vasculitis). Finally, it has already be found elevated in this group of diseases. The investigators hypothesized that s-CD95-L levels might be a prognostic factor in ANCA associated vasculitis and the study of the molecular mechanisms involved could provide new therapeutic targets.

The study will recruit 50 patients with ANCA associated vasculitis followed in Bordeaux University Hospital. Among classical disease activity information, blood and urine samples will be collected at each visit to study s-CD95-L. Fundamental research will be realized on patients' sample to study molecular mechanisms involved.

Clinical and biological disease activity, treatment and outcomes will be studied in correlation with s-CD95-L to describe their potential prognostic role. Patients will be followed at regular intervals, as their usual follow-up would request. No extra visit will be needed and blood samples will be drawn at the same time as those drawn for clinical purposes.

Inclusion Criteria:

• Diagnosis of ANCA associated vasculitis according to the Chapel-Hill Consensus Conference - 2012 modified version
• Age ≥ 18 years
• being affiliated to health insurance
• willing to participate and to sign informed consent.

Exclusion Criteria:

• Pregnant or breastfeeding women,
• patient concerned by articles L 1121-5 to L 1121-8 (persons deprived of their liberty by a judicial or administrative decision, minors, persons of legal age who are the object of a legal protection measure or unable to express their consent)