Abatacept

Abatacept sold under the brand name Orencia, is a medication. It is used to treat autoimmune diseases like rheumatoid arthritis, by interfering with the immune activity of T cells. It is a modified antibody.

Abatacept is a fusion protein composed of the Fc region of the immunoglobulin IgG1 fused to the extracellular domain of CTLA-4. In order for a T cell to be activated and produce an immune response, an antigen-presenting cell must present two signals to the T cell.