K. Soderhall Crustaceans lack immune memory and have therefore to rely on innate immune reactions. One such reaction is the clotting process which is very efficient and rapid and consists of a clotting protein present in plasma and a transglutaminase in the blood cells. The clotting protein has been cloned and belongs to the vitellogenin superfamily of proteins. Clotting proteins have also been purified from shrimp and they are very similar in properties to that of crayfish. Another innate immune defense process is the so-called proPO-system which is a non-self recognition system and which upon activation by microbial products generates several factors which will aid in the elimination of foreign particles or parasites. This system has been studied in greatest detail in freshwater crayfish and most of the proPO-components have been purified and cloned. Recently, we have also been able to clone some proPO-components from a shrimp, Peneaus monodon. Cellular immune reactions are important in the defenee and two communicating proteins have been isolated and cloned and they are the beta-1,3-glucan and peroxinectin. Both of these proteins are associated with the proPO-system and of great surprise was the finding that peroxinectin had a functional peroxidase domain but peroxidase activity was not involved in the cell adhesion activity of peroxinectin and instead a KGD motif was found to be of importance. Recently antibacterial peptides have been characterized in shrimp and they have been named penaeidins. In this talk I attempt to review our recent findings of the proPO-system in crayfish and shrimp and how it functions in defense in crustacean animals.

(Department of Physiological Mycology, University of Uppsala, Villavagen 6, 752 36 Uppsala, Sweden) back