These include alefacept, a recombinant human fusion protein consisting of leukocyte-function-associated antigen (LFA) type 3 and IgG1 (approved for the treatment of psoriasis in 2003); and abatacept, a CTLA4-IgG fusion protein approved for the treatment of rheumatoid arthritis. Here, CTLA4 is linked to rheumatoid arthritis.