Lipid and Lipoproteoglycan Hemagglutinins from Nereis

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Little is known about the roles of lipids as specific recognition molecules although hemagglutination by lipids has been reported on several occasions. The composition, properties, and functions of lipid and lipoproteoglycan agglutinins, which have been isolated from Nereis coelomic fluid and coelomocytes, will elucidate their roles in the invertebrate immune response and their potential for recognizing specific cell receptors. While studying the phospholipid agglutinins from Nereis, it was discovered that aged preparations of synthetic unsaturated phosphatidylethanolamines are hemagglutinins. This observation opens up a second route to obtain appreciable quantities of a specific class of lipid agglutinin and to define the structural requirements which confer activity. Chemical analysis, chromatography (2D-TLC, HPLC) and spectroscopy (MS, FTIR and NMR) are being used to characterize the components and structures of these agglutinins. Red blood cell (RBC) binding and inhibitor profiles and the use of enzymically-modified RBC indicate range and specificity of binding. The effects of these agglutinins on other kinds of cells are being determined. Light and electron microscopy (EM) are being used to visualize these interactions and the structures of the lipid aggregates will be studied using EM and 31 P NMR (for phospho-lipid agglutinins). Specific receptors on susceptible cells will be isolated. The information from these studies will define the structures and aggregation state of exogenous lipids which act in a bi- or multi-valent manner on specific cell surfaces, suggest what kind of binding is taking place, predict the behavior of other natural or synthetic lipids, and suggest ways in which lipids, as reagents, can be used in cell manipulation. Cell-surface interactions mediated by lipids have received very little attention, although scattered reports have suggested that lipids may play such a role. Further study of the role of lipids and lipoproteoglycan agglutinins in the immune-like defense mechanisms of the marine worm, Nereis, promises to provide important new insights into the more general role of lipids in specific cellular recognition phenomena.