Complement Regulatory Proteins Expression and Clinical Response in Rheumatoid Arthritis (RA) Patients Treated With Rituximab

Inclusion Criteria: 1. Patients of both gender, aged greater than or equal to 18 years; and lower than 70 years. 2. Patients diagnosed with RA for at least 6 months according to the criteria of the American College of Rheumatology (ACR) in 1987 for classification of AR. 3. Patients with a medical indication for therapy with rituximab, with prescription of this therapy for the first time and have not yet received the first dose. 4. DAS28 score greater than or equal to 3.2. 5. Use of adequate contraception, as judged from the attending physician. 6. Desire to participate voluntarily, the ability to understand the protocol, documented by signing the consent form (attached). Exclusion Criteria: 1. overlapping rheumatic disease, autoimmune lymphoproliferative and neoplastic. 2. active infection, patients with the use of cytotoxic drugs, presence of positive serology for HCV, HBV and HIV, active or latent tuberculosis. 3. allergy or hypersensitivity to rituximab. 4. pregnant woman or performing breastfeeding. 5. participating in another clinical study with intervention. 6. with functional class IV defined based on the criteria of Steinbrocker functional classification for RA. 7. prior therapy with Rituximab.