Sphingolipids and the regulation of the immune response.

Over the last decade evidence has accumulated that sphingolipids are important and specific signalling molecules for cell-to-cell communication (mediator function) as well as for intracellular signalling processes (second messenger function). In addition, glycosylated sphingolipids are essential building blocks of rafts thereby participating in the initiation of receptor mediated signalling events. In immunology, processes such as T cell apoptosis, Th1 versus Th2 T cell differentiation, phagocytosis, and allergic excitability are either influenced or directly regulated by this class of lipids. Models such as the 'dual function concept' (differentiation of structural components versus signalling molecules) and the 'rheostat concept' (the balance of two or more sphingolipids is essential for the biological function) describe the multiple properties of these signalling molecules.