This 14-week study will observe the gene expression of certain immune cells in patients with rheumatoid arthritis who receive etanercept, infliximab, and adalimumab. Patients at the National Institute of Rheumatology and Physiotherapy, Budapest, who are already scheduled to receive an anti-TNF agent will be asked to participate in this study. Patients will receive their treatment (etanercept, infliximab, or adalimumab) as scheduled, and have blood samples collected during the study and analyzed by the laboratory. Patient's response to their treatment will also be studied based on x-rays and other examinations.