Blood test in Rheumatoid Arthritis (RA) patients with good response to anti-Tumor Necrosis Factor (anti-TNF) and in patients with moderate or non-response will be done in the month following the evaluation of clinical response to therapy. Isolation of mononuclear cells and purification of monocyte by negative selection. Cell culture of monocyte in presence or not of anti-TNF for 24 hours and analyze of CD36 (cluster of differentiation antigen 36) expression (principal outcome). For secondary outcomes analyze monocyte phenotype, NRF2 nuclear translocation, and clinical data of patients.

Inclusion Criteria:

• RA defined according to the American College of Rheumatology (ACR) 2010 criteria,
• treated by anti-TNF + methotrexate, good responders in in one arm, and moderate or non-responders in the other arm according to EULAR (European Ligue Against Rheumatism) response criteria after three months of treatment

Exclusion Criteria:

• contra-indication to anti-TNF
• corticosteroid more than 10mg by a day equivalent prednisone,
• modification of DMARD (disease-modifying antirheumatic drugs) in the last three months
• comprehension trouble
• Factors modifying CD36 -cluster of differentiation antigen 36- expression as diabetes mellitus, kidney disease, HIV