ANCA-associated vasculitis is a serious autoimmune disease. The standard treatment is rituximab (RTX), which depletes B-cells to control inflammation. However, identifying patients at high risk of relapse remains a challenge, often leading to unnecessarily long treatments and side effects. Recent research suggests that RTX also impacts CD8+ T-cells, which could serve as valuable markers for better disease monitoring.

The main goal of the NALVANCA cohort is to identify biomarkers within these CD8+ T-cells. Researchers aim to find biological signals that respond to treatment and can predict a relapse. By studying these markers at the start of therapy and during the immune recovery phase, the study hopes to personalize treatment duration and management for each patient.

Recruitment targets adult patients diagnosed with ANCA-associated vasculitis. Participants must provide written informed consent for the use and storage of their blood samples in a biocollection. The protocol involves long-term monitoring with regular sampling to track changes in immune cells alongside the patient's clinical health.

Inclusion criteria :

• Adult patient (age ≥ 18 years).
• Patient affiliated with the French social security system.
• Seropositive ANCA-associated vasculitis (AAV) (positive for anti-PR3 or anti-MPO) meeting the Chapel-Hill classification criteria.
• Patient scheduled to receive rituximab (RTX) maintenance therapy (500 mg every 6 months) following an initial flare or a relapse of the disease.

Exclusion Criteria:

• Patient unable to provide informed consent.
• Patient refusing to participate in the study.
• End-stage renal disease.
• Progressive neoplasia (excluding cutaneous carcinomas)

The study population includes adults treated in Nantes, Saint-Nazaire, or La Roche-sur-Yon for ANCA-associated vasculitis (GPA or MPA). These patients, positive for anti-PR3 or anti-MPO antibodies, are recruited during a flare or relapse and receive Rituximab therapy. Samples are provided by the NALVANCA Biocollection.