Review

In this work data on immune cell signallling in the circulating hemocytes of the edible bivalve, the mussel Mytilus spp, are summarized. Studies with different bacteri l species and strains, heterologous cytokines and natural hormones, as well as with organic environmental chemicals, led to the identification of the role of conserved components of kinase-mediated transduction pathways, including cytosolic kinases (such as MAPKs and PKC) and kinase-activated transcription factors (such as STATs, CREB, NF-kB), in the immune response. From these data a general scenario emerged indicating that close similarities exist in the signalling pathways involved in cell mediated im unity in bivalve and mammalian immunocytes. In particular, the results indicate that bo h e extent and duration of activation of components of kinase-mediated cascades are crucial in determining the hemocyte response to extracellular stimuli. The identification of the basic mechanisms of immunity and its modulation in mussels can give important information for the possible utilization of these species as an invertebrate model for studies on innate immunity. Moreover, the application of this knowledge to the understanding of the actual adaptive responses of bivalves when exposed to micro-organisms in their natural environment can represent significant ecological, economical and public health-related interest. Key words: Mytilus; hemocytes; innate immunity; kinase-mediated cell signallin