Allograft Inflammatory Factor-1 (AIF1)or ionized calcium-binding adaptor molecule 1 (Iba1) is expressed selectively in microglia/macrophages and is a Ca2+-binding peptide produced by activated monocytes and microglial cells. It has been suggested that AIF1 expression is associated with chronic inflammatory processes. AIF1 is expressed by activated monocytes and might participate in a variety of pathogenic processes in the mammalian brain and in chronic transplant rejection. It has been shown to be expressed early and persistently in chronically rejecting cardiac allografts but not in cardiac syngrafts and host hearts.