Allograft Inflammatory Factor-1 (AIF1) is a 17 kDa. cytoplasmic, calcium and actin binding scaffold protein, mainly expressed in immunocytes. AIF-1 is induced by cytokines such as interferon-γ (IFN-γ).

It is encoded within the HLA class III genomic region by IBA1 gene, and its structure contains seven alpha helixes and three beta sheets. There are three other proteins identical to AIF1: Ionized Ca²⁺-Binding Adaptor 1, Microglia Response Factor-1, and Daintain¹.

The gene is highly expressed in testis, spleen, circulating macrophages and in the brain but weakly expressed in lung and kidney. Among brain cells, the Iba1 gene is strongly and specifically expressed in microglia and its expression is up-regulated following nerve injury, central nervous system ischemia, and several other brain diseases².

AIF1 influences the immune system at several key points and thus modulates inflammatory diseases. It increases the expression of inflammatory mediators such as cytokines, chemokines, inducible nitric oxide synthase (iNOS) and promotes inflammatory cell proliferation and migration and hence it is highly associated with autoimmune diseases³. In addition, its abundance is positively correlated with metabolic indicators, such as body mass index, triglycerides, and fasting plasma glucose levels. There is also evidence that AIF1 could be a marker for diabetic nephropathy when detected in serum. It is found in activated macrophages in the pancreatic islets, and has been shown to decrease insulin secretion, while simultaneously impairing glucose elimination⁴.