Low plasma antibodies specific for phosphatidylethanol in alcohol abusers and patients with alcoholic pancreatitis

Phosphatidylethanol (PEth) is a group of alcohol-modified phospholipids present in cell membranes after heavy drinking. Our aim was to demonstrate the presence of human plasma antibodies binding to PEth and to address their specificity and value in detecting subjects engaged in heavy alcohol consumption. Antibodies to PEth were analyzed in plasma from heavy drinkers (n=20), patients with alcoholic pancreatitis (n=58) and control subjects (n=24), using chemiluminescent immunoassay. Heavy drinkers and patients with alcoholic pancreatitis demonstrated significantly lower levels of plasma IgG, IgA and IgM titers to PEth compared with controls (P<0.001). The specificity of the antibodies to PEth was demonstrated with competitive liquid phase immunoassays and flow cytometry. The plasma IgG, but not IgA or IgM, titers to PEth in heavy drinkers correlated with the whole blood PEth concentration determined by liquid chromatography-mass spectrometry (r=0.655, P=0.002). Compared with traditional markers for alcohol abuse (aspartate aminotransferase, gamma-glutamyl transpeptidase and mean corpuscular volume), receiver operating characteristic curve analysis showed that a low plasma IgA to PEth had the highest area under the curve (AUC 0.940, P<0.001). In conclusion, plasma IgG, IgA and IgM antibodies binding specifically to PEth were found in subjects of all study groups. Subjects with heavy alcohol consumption showed markedly lower plasma immunoglobulin levels to PEth, potentially making them useful as a biomarker to distinguish heavy from moderate alcohol use.

Immunohistochemical distribution of phosphatidylglucoside using anti-phosphatidylglucoside monoclonal antibody (DIM21)

The immunohistochemical distribution of phosphatidylglucoside (PhGlc) in organs obtained from human autopsy cases was investigated using the DIM21 antibody. Immunohistochemical staining was performed on formaline-fixed, paraffin-embedded sections using the simple stain peroxidase method. The sections were then subjected to antigen retrieval by microwave irradiation in citrate buffer. PhGlc expression was observed in not only the epithelial but also the non-epithelial components of several visceral organs. Squamous and glandular epithelial cells were positive for PhGlc in several organs. The surface areas of the epithelium, particularly the squamous epithelium, were positive. Mesothelial cells were also positive in some organs. Endothelial cells, polymorphonuclear (PMN) cells are positive in several organs. Macrophage is positive in many organs. Epithelial cells of the gallbladder were positive, however, the intrahepatic bile ducts were not positive. In the brain tissue, astroglial cells, the chorioide plexus, the pituitary gland, and ependymal cells were positive. Further investigation is indispensable in order to establish a relationship between cell differentiation and PhGlc expression.

Phosphatidylglucoside: a new marker for lipid rafts

Lipid rafts are functional microdomains enriched with sphingolipids and cholesterol. The fatty acyl chain composition of sphingolipids is a critical factor in the localization of lipids in lipid rafts. The recent studies suggest that lipid rafts are more heterogeneous than previously thought. In addition, our discovery of a new glycolipid, phosphatidylglucoside (PtdGlc), also supports the notion of raft heterogeneity. The complete structural characterization of PtdGlc shows that it consists solely of saturated fatty acyl chains: C18:0 at the sn-1 and C20:0 at the sn-2 positions of the glycerol backbone. This unique fatty acyl composition comprising a single molecular species rarely occurs in known mammalian lipids. Although the structure of PtdGlc is similar to that of phosphatidylinositol, PtdGlc localizes to the outer leaflet of the plasma membrane and is possibly involved in cell-cell interaction signaling in the central nervous system.

Comprehensive analysis of monoclonal antibodies against detergent-insoluble membrane/lipid rafts of HL60 cells

Glycosphingolipids and cholesterol are principal components of plasmamembrane microdomains, i.e. lipid rafts. Recent studies revealed the possible presence of a variety of microdomains that distinctly differ in terms of their molecular composition and functions. To understand their precise structures and functions, we produced monoclonal antibodies (MAbs) by immunizing mice to the microdomains prepared from a fraction of detergent-insoluble membrane (DIM) of HL60 cells. Biochemical characterization of the antigen epitopes led to classification of the MAbs into two groups. One group consists of MAbs that react with lipids such as phosphatidylglucoside, lysophosphatidylinositol, and gangliosides (GM1a and GD1b), and the other consists of MAbs that react with proteins such as annexin I, aminopeptidase N and acrogranin. Immunofluorescence staining of HL60 cells with the MAbs, except for the MAbs that recognize lysophosphatidylinositol or annexin I, resulted in patchy-like images of the cell membranes. Interestingly, MAbs belonging to the former group had the potential to induce cell proliferation/differentiation in vitro. Our MAbs against the DIM fraction of HL60 cells can be valuable tools for the study of membrane microdomains.

A new phosphoglycerolipid, ‘phosphatidylglucose’, found in human cord red cells by multi-reactive monoclonal anti-i cold agglutinin, mAb GL-1/GL-2

Cord red cell membranes express many differentiation-related molecules. To study such molecules, we have established human cell lines, termed GL-1 and GL-2, by the Epstein-Barr virus transformation method, both of which produce monoclonal anti-i cold agglutinin [Y. Nagatsuka et al., Immunol. Lett. 46 (1995) 93-100]. Thin layer chromatography immunoblotting analysis revealed that these antibodies had broad specificities reacting with a variety of glycolipid antigens. Of the immunoreactive lipid antigens, a new phosphoglycerolipid containing glucose from human cord red cells was found. The isolated lipid was unstable to alkaline hydrolysis and contained glucose as a sole sugar. Secondary ion mass spectrum-collision-induced dissociation mass spectrometric analysis of this lipid gave the main molecular ion peak at m/z 885 corresponding to phosphatidylhexose. This antigen was susceptible to phospholipases A2, C and D but resistant to phosphatidylinositol-specific phospholipase C. Two-dimensional nuclear magnetic resonance spectroscopy confirmed that glucose is linked to the sn-glycerol 3-phosphate residue with a beta-anomeric configuration. Based upon these combined results, we identified this lipid as phosphatidyl-beta-D-glucose. This is the first report showing the presence of the glucosylated glycerophospholipid in mammalian sources.