Summary

The hemocytes are the cells responsible for the immunity in molluscs. Cytokines, growth factors, etc, present in the soluble fraction of the hemolymph modulate the immune response. The inflammatory cytokine interleukin-2 (IL-2) induces the synthesis of nitric oxide (NO), responsible for oxidizing processes. In hemocytes of mollusks, the presence of IL-2 induces the synthesis of the three subunits of the receptor of high affinity, and the subsequent activation of the signaling pathway where the cAMP-dependent protein kinase (PKA) plays the main role, with a secondary role of PKC. In the presence of IL-2, PKA activates NO synthesis through the constitutive enzyme mc-NOS. In winter, the action of PKC on a novel inducible form mw-NOS leads to an increase of the IL-2-induced NO synthesis. According to our studies, this set of metabolic reactions explains the seasonal variations in NO production by hemocytes of Mytilus galloprovincialis. However, after two years of studies, and coinciding with the Prestige oil spill in November 2002, this effect was cancelled for at least the two years following the catastrophe