Cell signalling in the immune response of mussel hemocytes

Abstract

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 bacterial 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 immunity in
bivalve and mammalian immunocytes. In particular, the results indicate that both the 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 microorganisms in their natural environment can represent significant ecological, economical and public health-related interest.