Stress-based modulation of the immune response in molluscan hemocytes: a two-receptor model

In molluscs, hemocytes perform the molecular mechanisms related to immunity. These cells have the ability to respond to the different varieties of stress by modulating their responses. The stressors may be bacterial toxins, cytokines or growth factors, and even physical agents such as changes in temperature or oxygen partial pressure. In the first place, hemocytes synthesise catecholamines, which, in turn, modify the immune response in terms of phagocytosis or nitric oxide synthesis. According to studies on the hemocytes of the mussel Mytilus galloprovincialis, we propose a model for a sequential action where the IL-2 receptor and its wide agonist specificity play an important role. Also, α and β-adrenergic receptors suggest the functioning of a return-to-hemocyte mechanism. The model is proposed taking into account the possible relationship between the pathways mediated by cAMP-activated protein kinase and protein kinase C in hemocytes.