Regenerating islet-derived 3 (REG3) proteins belong to the family of C-type lectins (Cash HL et al. 2006a,b; Lehotzky RE et al. 2010). REG3A and REG3G are expressed in the intestine where they moodulate the host interactions with commensal and pathogenic gut bacteria. REG3 proteins bind the peptidoglycan moieties of bacteria inducing damage to the bacterial cell wall. The antibacterial activities of REG3 proteins are restricted to Gram-positive bacteria and are tightly controlled by an inhibitory N-terminal prosegment that is removed by trypsin in vivo (Cash HL et al. 2006; Mukherjee S et al. 2009; Medveczky P et al. 2009).