AIF1 and rheumatoid arthritis: Allograft inflammatory factor 1 (AIF-1) was originally identified as an IFN-γ–inducible, Ca2+-binding cytosolic protein (18) that is primarily expressed in MΦs (19, 20) and has since been implicated in several inflammatory diseases including autoimmune encephalitis (21), diabetes (22), rheumatoid arthritis (23), and chronic cardiac and liver allograft rejection (24, 25).