HRF (histamine-releasing factor), also known as TCTP, TPT1, p02, and fortilin, is a member of the TCTP family of calcium-binding proteins. It is widely expressed and apparently serves as a transcriptional activator, calcium transporter, histamine inducer, and antiapoptotic, caspase-3 inhibitor. HRF, in addition to functioning as a histamine-releasing factor, can modulate secretion of cytokines from human basophils, eosinophils, T cells, B cells, and epithelial cells. HRF knockout mice were embryonic lethal. Transgenic mice models have shown that HRF augments the inflammatory response to allergens.