Study of the IgA Repertoire During IgA Deposition Nephropathy.

IgA plays a major role in mucosal and systemic immunity but retains mysterious and ambivalent aspects. They can thus, depending on the situation, prove to be capable of triggering either a protective inflammatory response or, on the contrary, anti-inflammatory and inducing tolerance. Similarly, and for reasons that remain very poorly understood, they can be involved in pathologies where the immune system is itself an aggressor of the body and responsible for immunopathological lesions. The investigator formulates the hypothesis that an inappropriate response of the mucosal immune system to one or more antigens leads to a synthesis of IgA of bad affinity favoring a deposit at the level of the mesangium. It seems important to verify this point by analyzing the IgA repertory of patients with N-IgA and comparing it to that of a control population.

Inclusion Criteria: * Control population: * person between the ages of 18 and 55 (persons matched to age and sex (75% male) (N-IgA is more common in humans) free from any pathology. oAbsence of proteinuria and hematuria on urine sample (search by strip). * Patients with N-IgA * 40 patients with N-IgA whose diagnosis was confirmed by renal biopsy. These may be previously known patients who have not received treatment with corticosteroids or immunosuppressants for 12 months or new patients. The incidence of N-IgA is 20 patients per Mh; the number of incident patients with N-IgA is 10-15 per year in the nephrology department. The recruitment of 40 patients over 1 year is feasible. * Participant's written consent Exclusion Criteria: * Secondary or associated N-IgA (infection, malignant disease, inflammatory bowel disease, * Rheumatic autoimmune disease or other; * treatment with corticosteroids or immunosuppressants for less than 12 months. * person on dialysis