<qa>  What is the primary endpoint of the study?25 participants with RA who have bad prognostic genetic markers Anti-citrullinated protein antibodies ACPA and human leukocyte antigen HLADR4 and who were scheduled to receive subcutaneous abatacept as part of their standard clinical treatment will be recruited. Consenting participants will followed for a total of 24 weeks during which time they will have additional venous blood and urine samples taken to investigate the effects of abatacept on their immune cells and system. The primary endpoint of the study is the characterisation of the immune response following costimulatory modulation in RA patients at 12 weeks. Secondary endpoints include change in immunological response and its association with clinical outcome measures up to 24 weeks. 