Reg3A (Regenerating islet‑derived protein 3 alpha), also known as Reg III‑ alpha PAP2 (pancreatitis‑associated protein 2) in rats, or HIP/PAP (human islet peptide/PAP) in humans, is a secreted 16‑17 kDa type III member of the Reg family, which is the group 7 subfamily of C‑type lectins (1, 2). The four type III genes ( alpha -δ) in the mouse Reg family are thought to have cell‑protective and proliferative effects (2‑4). Like other Reg proteins, the 149 amino acid (aa) mature mouse Reg3A (aa 27‑175) contains a small, trypsin‑cleavable PAP domain (aa 27‑39) and a C‑type lectin domain (2, 5).  Mature mouse and rat Reg3A share 87% aa sequence identity, while human Reg3A shares 61%, and other mouse type III Regs share less than 60% aa sequence identity with mouse Reg3A. Rodent Reg3A is mainly expressed in the intestinal tract and acinar cells and islet alpha cells of the exocrine pancreas; IL‑6 enhances the expression of Reg3A (1, 3, 6, 7). Pancreatic Reg3A expression is also increased in mouse models of type 1 diabetes (4). In the rat brain, nerve injury and inflammation increase Reg3A expression in dorsal root ganglion neurons, while low dopamine levels in stress induce its production by melanocytes (8, 9). Treatment of rat macrophages with Reg3A causes up‑regulation of NFkB signaling and modulates cytokine production (2, 10). In humans, Reg3A expression and proteolytic activation in the small intestine is thought to have a protective effect against infection and TNF‑ alpha ‑induced stress (11).