Regenerating islet-derived protein 3-gamma (Reg3G), also known as pancreatitis-associated protein 3 (PAP3), is one of several secreted Reg proteins that contain a single C-type lectin domain and contribute to anti-microbial immunity in the gut (1, 2). Reg3G is secreted as a 148 amino acid (aa) proprotein, and 11 residues are cleaved from the N-terminus to generate the 15 kDa mature protein (3). This short propeptide serves as an inhibitor that limits the activity of the proprotein (3, 4). Mature mouse Reg3G shares 66% and 88% aa sequence identity with human and rat Reg3G, respectively. Reg3G is expressed by Paneth cells of the small intestine and is released into the gut lumen (5). It is up-regulated in gastrointestinal epithelium by bacterial inflammation or by defects in the mucous lining (5-8). Its expression and secretion is also induced in the lung in response to MRSA (drug resistant S. aureus) and in damaged skeletal muscle and peripheral neurons (4, 9). Reg3G binds to bacterial peptidoglycans, exerts bacteriostatic and bactericidal activities, and protects the mucosa against bacterial invasion (4, 5, 10, 11). It also inhibits inflammation by limiting the number of Th1 cells in the lamina propria (11). R&D in-house data indicate that Reg3G can induce the proliferation of Schwann cells, a property it shares with Reg3B (12).