Human Tumor Necrosis Factor Alpha (TNFa)-Induced Pre-B Cell Bone Marrow Emigrants

Primary Objective: The primary objective of the study is to identify early B cell bone marrow emigrants in the peripheral blood of adults with rheumatoid arthritis (RA) receiving etanercept. Hypotheses: We believe that the peripheral blood of RA patients contain early B cell bone marrow emigrants. We believe that these early B cell bone marrow emigrants are induced by TNFα. Primary Endpoint: The primary endpoint of the study is quantification of CD34+/CD19+ early B cell bone marrow emigrants in the peripheral blood of subjects. Study Design: Open-label, One Arm, Phase IV study of 12 RA patients with active disease receiving etanercept.