Neprilysin (NEP) represents an important enzyme in both vertebrates and invertebrates. In the present report we have focused our attention to invertebrates. In particular, a structure related to CD10/NEP as well as its activity in different tissues, such as immunocytes, nervous tissue and muscle of various species were detected. Moreover, the role played by the enzyme in the interactions between host and parasite has also been reported. The findings indicate that NEP immunoregulation is a wellbalanced process that, with appropriate physiological and homeostatic responses to challenges, allows the survival and well-being of the species.