B cells are known to play an important role in auto-immune diseases by activating T cells, secreting inflammatory cytokines and autoreactive antibodies. However, a sub-type of B cells named regulatory B cells or Bregs has recently shown capacities to prevent or cure arthritis in mouse models. Bregs have also been identified in humans.

B cells are known to play an important role in auto-immune diseases by activating T cells, secreting inflammatory cytokines and autoreactive antibodies. However, a sub-type of B cells named regulatory B cells or Bregs has recently shown capacities to prevent or cure arthritis in mouse models. Bregs have also been identified in humans. Main objective: To study Bregs abnormalities in patients with rheumatoid arthritis (RA) at different stages of the disease compared to subjects with mechanical pathologies.Secondary objectives:- To evaluate the specificity of any abnormalities identified in RA by studying Bregs in patients with other autoimmune or other inflammatory joint diseases.- To evaluate the effect of biological and synthetic treatments on Bregs in patients with RA. - To assess whether the rate of Bregs before treatment is predictive of response to biological and synthetic treatments.

Inclusion Criteria:

For RA patients and control patients:

• Age over 18 year old
• Blood sample taken as part of the usual management
• Steroid less than or equal to 15 mg/day and stable for at least a week

For RA patients:

• Patient with RA meeting the ACR / EULAR 2010

For control patients:

• Patients with systemic autoimmune disease (lupus, Sjogren's syndrome, scleroderma) or other inflammatory arthritis (spondylitis, crystals) or a mechanical pathology (limb osteoarthritis or spinal pathology) .

Exclusion Criteria:

• steroids over 15 mg/day
• rituximab infusion in less than 12 months

Patients and controls will be recruited in the Immuno-rheumatology Service of the University Hospital of Montpellier.

They will be recruited during consultations or hospitalizations, when a blood sample is planned within the framework of their usual follow-up.