AIF1

AIF1, short for allograft inflammatory factor 1, is a gene that encodes a small cytoplasmic calcium-binding protein also known as IBA1 (ionized calcium-binding adaptor molecule 1). In humans, the AIF1/IBA1 protein is widely used as a marker of microglia and macrophages, reflecting their activation state in various tissues.

Structure and expression: The AIF1 protein is characterized by calcium-binding motifs and localizes to the cytoplasm, where it can associate with membranes and the actin cytoskeleton. It is expressed constitutively at low levels in monocytes and macrophages and is enriched in microglia within the central nervous system. Expression levels rise in response to inflammatory stimuli and tissue injury, making AIF1 a commonly assessed indicator of inflammatory cell activation.

Function: AIF1/IBA1 is implicated in processes related to cytoskeletal remodeling, cell motility, and phagocytosis. It participates in membrane ruffling and may influence the migration and phagocytic activity of macrophages and microglia. The protein’s activity is linked to calcium signaling and, in turn, to the regulation of inflammatory responses.

Clinical and research relevance: Because of its restricted and inducible expression in activated macrophages and microglia, AIF1 is frequently used in histology and molecular studies to identify these cells and to gauge inflammatory activation in tissues. Elevated AIF1 expression and IBA1 immunoreactivity have been reported in models of neuroinflammation and various neurodegenerative or inflammatory diseases, though the marker is not disease-specific.

Overall, AIF1 serves as a useful, broadly applicable marker of macrophage/microglial presence and activation, with functional relevance to cytoskeletal dynamics and inflammatory signaling.