Abatacept is a newly approved treatment for rheumatoid arthritis refractory to other agents. Abatacept is a fusion protein of the cytotoxic T‐lymphocyte antigen (CTLA) molecule and immunoglobulin (Ig) G1 that blocks CD28. Specifically, abatacept blocks the CD80 and CD86 ligands on the surface of antigen‐presenting cells that must interface with the T‐cell's CD28 receptor to activate T cells. Abatacept seems to be more immunosuppressive than tumor necrosis factor alpha blockers. The combination of abatacept and a tumor necrosis factor alpha blocking agent does not seem more effective than either agent alone. Because abatacept has the ability to suppress T‐cell function, it has the potential to be a treatment for psoriasis and other autoimmune conditions involving pathologic processes driven by T cells.