Original involvement of antimicrobial peptides in mussel innate immunity

Recently, the existence and extended diversity of antimicrobial peptides ha s been revealed in two mussel species. These molecules are classified into four groups according to common features of their primary structure: defens ins, mytilins, myticins and mytimycin. In Mytilus galloprovincialis, gene s tructure reveals synthesis as precursors in circulating hemocytes. Synthesi sed even in absence of challenge, the precursors mature and the peptides ar e stored in granules as active forms. The different peptides are engaged in the destruction of bacteria inside phagocytes, before being released into hemolymph to participate in systemic responses. Such involvement in anti-in fectious responses is unique, and apparently more related to those of mamma lian phagocytes than to those of insects. (C) 2000 Federation of European B iochemical Societies. Published by Elsevier Science B.V. All rights reserve d.