This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project is designed to test whether addition of Abatacept to a 24-week induction protocol involving cyclophosphamide followed in turn by azathioprine can induce remission with greater frequency than treatment with cyclophosphamide and azathioprine alone. Secondary objectives are to determine the safety of the agent, the durability of the response when the immunosuppressive medications are stopped and the partial response rate. Finally, a third secondary objective is to ascertain whether the Abatacept enables greater response to vaccinations compared to therapy with cyclophosphamide alone.