<qa>  What is RA?Rheumatoid arthritis RA is a chronic inflammatory immune mediated arthritis which leads to pain, swelling and destruction of joints. RA affects more than 500,000 subjects in the United Kingdom UK and incurs significant health and economic cost. Most patients require potent immune suppressing drugs such as methotrexate, which help reduce pain and stiffness, and protect the joints against damage. However, many patients do not respond or are unable to tolerate methotrexate. In these patients, biologic drugs such as abatacept are used to try to control the arthritis. 