Lipid Rafts of Neutrophils

The neutrophilic granulocytes (neutrophils) are the most abundant leukocytes in blood. They present the ferst line of defence against pathogenic microbes having a variety of defence mechanisms at their disposal. In case of an inflammation, the neutrophils are attracted by specific substances (chemotaxis) and thereby move from the blood circulation through the vessel walls to the site of inflammation (diapedesis). At this site they engulf the microbes (phagocytosis) and kill them by oxygen radicals and other antimicrobial substances. They are also capable of directly expelling antimicrobials and various enzymes (exocytosis). This variety of neutrophil functions is correlated with a variety of cytoplasmic granules (4 types) which contain the effective substances for their different tasks. Recently it was shown that the specific functions of neutrophils depend an intact lipid-protein microdomains, socalled "lipid rafts", in diverse membranes. These domains are rech in cholesterol and sphingolipids and contain distinct membrane proteins which are involved in signal transduction through the membrane. In the proposed project, we want to study extensively the lipid-protein domains of neutrophils using biochemical and microscopic techniques and correlate them with the specific neutrophil functions like chemotaxis, phagocytosis, and exocytosis. These studies will be carried out an isolated neutrophils and an cultivated neutrophil-like cells. The cultivated cells will be manipulated by molecular biological techniques with the effect that distinct lipid raft proteins can be visualized in live cells by fluorescence microscopy. Observing these cells during chemotaxis, phagocytosis, and exocytosis will gradually unravel the functions of membrane microdomains during neutrophil actions. Our data will shed light an the effector functions of these important immune cells under normal conditions and in case of genetic defects.