The identification of CTLA4 as an important immune regulator has also led to the discovery of a fusion protein consisting of the extracellular domain of CTLA4 fused to the Fc region of IgG1 (abatacept and belatacept), acting as a CTLA4 mimetic and helping to restrain the inflammatory manifestations in rheumatoid arthritis [26]. Here, CTLA4 is linked to rheumatoid arthritis.