Ceramide Tetrasaccharide Research Articles

Structural studies on the neutral glycosphingolipids of Manduca sexta

Glycosphingolipids (GSLs) have been implicated as playing major roles in cellular interactions and control of cell proliferation in muticellular organisms. Moreover GSLs and other sphingolipids such as sphingomyelins, ceramides and sphingosines serve a variety of roles in signal transduction. Hence, identification of structures of GSLs in different biota will shed light in understanding their physiological role. During this study, the major glycosphingolipid component present in the extracts of stage-12 and stage-17/18 metamorphosing adults of Manduca sexta was identified as mactosyl ceramide. We report the isolation of several ceramide disaccharides, a ceramide trisaccharide and a ceramide tetrasaccharide. The GSL structures were confirmed by high-resolution mass spectrometry and tandem mass spectrometry. The identity of the monosaccharides was proved using exoglycosidases. The predominant sphingosine chain-length varied from C-14 (tetradecasphing-4-enine) to C-16 (hexadecasphing-4-enine) in these GSLs. Sphingosines of both chain lengths were accompanied by their doubly unsaturated counterparts tetradecasphinga-4,6-diene and hexadecasphinga-4,6-diene. It is also interesting to note the presence of tetradecasphinganine and hexadecasphinganine in minute amounts in the form of a GSL in the extracts of M. sexta. The varying degrees of unsaturation in the sphingosine moiety of GSLs in M. sexta may be biologically significant in insect metamorphosis. The ceramide trisaccharides and ceramide tetrasaccharide belong to the arthro-series, The observation of fucose in the M. sexta GSLs is the first report of the presence of fucose in an arthroseries GSL.

Mixed lipid aggregates containing gangliosides impose different 2H-NMR dynamical parameters on water environment depending on their lipid composition.

Water dynamics in samples of ceramide tetrasaccharide (Gg4Cer) vesicles and GM1 ganglioside micelles at 300:1 water/lipid mole ratio were studied by using deuterium nuclear magnetic resonance (2H-NMR). GM1 imposes a different restriction on water dynamics that is insensitive to temperatures either above or below its phase transition temperature or below the freezing point of water. The calculated correlation times are in the range of 10(-10) s, typical of water molecules near to the polar groups. Pure GM1 micelles have two distinct water microenvironments dynamically characterized. Their dynamic parameters remain constant with temperature ranging from -18 to 32 degrees C, but the amount of strongly associated water is modified. By contrast, a mixture of single soluble carbohydrates corresponding to GM1 polar head group does not preserve the dynamic parameters of water hydration when the temperature is varied. Incorporation of cholesterol or lysophosphatidylcholine into GM1 micelles substantially increases the mobility of water molecules compared with that found in pure GM1 micelles. The overall results indicate that both the supramolecular organization and the local surface quality (lipid-lipid interaction) strongly influence the interfacial water mobility and the extent of hydration layers in glycosphingolipid aggregates.

Structural analysis of neutral glycosphingolipids from Ascaris suum adults (Nematoda:Ascaridida).

The neutral glycosphingolipid fraction from adults of the pig parasitic nematode, Ascaris suum, was resolved into four components on thin-layer chromatography. The high-performance liquid chromatography-isolated components were structurally analysed by: methylation analysis; exoglycosidase cleavage; gas-liquid chromatography/mass spectrometry; liquid secondary-ion mass spectrometry; and, in particular, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Their chemical structures were determined as: Glc(beta 1-1)ceramide, Man(beta 1-4)Glc(beta 1-1)ceramide, GlcNAc(beta 1-3)Man(beta 1-4)Glc(beta 1-1)ceramide and Gal(alpha 1-3)GalNAc(beta 1-4)GlcNAc(beta 1-3)Man(beta 1-4)Glc(beta 1-1)ceramide; and were characterized as belonging to the arthro-series of protostomial glycosphingolipids. No glycosphingolipid component corresponding to ceramide tetrasaccharide was detected during these analyses. The ceramide composition of the parent glycosphingolipids was dominated by the 2-(R)-hydroxy C24:0 fatty acid, cerebronic acid, and C17 sphingoid-bases: 15-methylhexadecasphing-4-enine and 15-methylhexadecaphinganine in approximately equal proportions. The component ceramide monohexoside was characterized by an additional 15-methylhexadecaphytosphingosine.

Glycosphingolipid composition of rat placenta: changes associated with stage of pregnancy

The composition of glycolipids and their changes in the placenta were investigated in the normal pregnant rat. Total lipid fractions extracted from the placenta between days 12 and 20 of pregnancy (day 0 = oestrus) were subjected to glycolipid analysis using DEAE-Sephadex chromatography, silica-gel HPLC, silica-gel TLC, TLC/immunostaining, matrix-assisted secondary-ion mass spectrometry in the negative-ion mode and 1H NMR. Glycolipids identified in the rat placenta were: gangliosides GM3 (NeuAcLacCer and NeuGcLacCer) and GD3 (NeuAcNeuAcLacCer, NeuAcNeuGcLacCer and NeuGcNeuAcLacCer), and neutral glycolipids ceramide monosaccharide (CMH) (GlcCer), ceramide disaccharide (CDH) (LacCer), ceramide trisaccharide (CTH) (Gb3Cer) and ceramide tetrasaccharide (CQH) (Gb4Cer). The content of neutral glycolipids was higher than that of gangliosides throughout pregnancy. Of the neutral glycolipids, CMH and CTH predominated and the level of CDH was low at mid-pregnancy. During late pregnancy, CMH and CTH decreased and CDH increased markedly. CQH remained at a low level throughout pregnancy. Of the gangliosides, GM3 was predominant on days 12-16 and then decreased, whereas GD3, which was low on day 12, increased slightly on day 16 and maintained the same level thereafter. Immunohistochemical studies indicated that these changes in the expression of major gangliosides from GM3 to GD3 occurred in labyrinthine trophoblasts. Thus expression of these glycolipids appears to change markedly during pregnancy.

Glycosphingolipids in cestodes. Chemical structures of ceramide monosaccharide, disaccharide, trisaccharide and tetrasaccharide from metacestodes of the fox tapeworm, Taenia crassiceps (Cestoda: Cyclophyllidea).

The presence of glycosphingolipids in the metacestodes of the fox tapeworm, Taenia crassiceps, has been established. The normal-phase TLC pattern of the neutral-fraction glycolipids revealed groups of bands corresponding to homologous components of increasing sugar chain length. The three simplest glycolipid components have been isolated and their chemical constitution determined as being of the neogala series: Gal beta 1Cer, Gal beta 6Gal beta 1Cer and Gal beta 6Gal beta 6Gal beta 1Cer. The ceramide tetrasaccharide fraction has been found to consist of a mixture of neogalatetraosylceramide, as an elongation of the neogala series, Gal beta 6Gal beta 6Gal beta 6Gal beta 1Cer and the component Gal alpha 4Gal beta 6Gal beta 6Gal beta 1Cer (both occurring in approximately equimolar proportions). The long-chain bases of the ceramide monogalactoside, digalactoside, trigalactoside and tetragalactosides contain, as well as small amounts of sphingosine, predominantly dihydrosphingosine/phytosphingosine in the approximate ratios 1.7:1, 1.4:1, 1:1 and 2.3:1, respectively. The major ceramide fatty acids have particularly long chains, with hexacosanoic and octacosanoic acids predominating. Upon reverse-phase TCL, the glycolipid components ceramide monogalactoside, digalactoside and trigalactoside were each separable into five component bands. Parent glycolipid components therefore show component band distributions comparable to one another in being governed by similar ceramide constitutions.

Immunogenic properties of mannose-containing ceramide tetrasaccharide from fresh-water bivalve, Hyriopsis schlegelii

Antisemirum against GlcNAcβ1 → 2Manαl → 3Manβ1 → 4Glcβ1→ 1Cer (MlOse 4Cer), a mannolipid isolated from spermatozoa of the fresh-water bivalve Hyriopsis schlegelii, was elicited in rabbits by repeated injection of a mixture of hapten-bovine serum albumin with Freund's adjuvant. The specificity of the affinity-purified antibody obtained from the serum was based on two forms of enzyme-immunodetection of its binding to structurally related glycolipids, either adsorbed to microtiter plates or chromatographed on thin-layer plates. The purified antibody exhibited a significant cross-reactivity with GlcNAcβ1 → 2Manαl → 3(Xylβ1 → 2)Manβ1 → 4Glcβ1 → 1Cer, (MlXOse 5Cer) containing a core structure closely related to MlOse 4Cer, but almost unrelated to other glycolipids. Distribution of MlOse 4Cer and MlXOse 5Cer in various bivalve and snail glycolipid extracts were screened in thin-layer immunobinding assays by using this purified specific antibody. The presence of the glycolipid antigens was limited to certain taxonomic orders of shellfish species.

Influence of glycolipids on immune reactions of phospholipid antigens in liposomes

Complement-dependent immune damage to liposomes mediated by a murine monoclonal antibody to the liposomal bilayer was completely inhibited by ceramide tetrasaccharide (globoside) at an 8% concentration in the liposomes. Lower concentrations of globoside, or higher concentrations of ceramide tri-, di-, or monohexoside, were not inhibitory. At a globoside concentration of 5.8%, inhibition of the monoclonal antibody activity was reduced and inhibition was related to antibody concentration; but at 2% globoside, suppression of antibody activity was not observed at all. Analysis of space-filling models revealed that at 8% globoside the distance between adjacent tetrasaccharides of globoside approached the dimensions of the antigen-binding end of a 7S immunoglobulin molecule. We therefore propose that globoside, and perhaps other glycolipids, can exert steric hindrance to the binding of extracellular proteins to nonglycolipid constituents of the lipid bilayer. We conclude that microheterogeneity among polar groups of glycolipids may be a novel mechanism for allowing selective access of proteins to phospholipids on the lipid bilayer.

Neutral glycosphingolipids of ova of the fresh-water bivalve, Hyriopsis schlegelii.

The neutral glycosphingolipids of ova of the fresh-water bivalve, Hyriopsis schlegelii were characterized. The most abundant glycolipid was ceramide monosaccharide, followed by ceramide trisaccharide, ceramide tetrasaccharide, and ceramide disaccharide. More complex neutral glycolipids accounted for almost one-third of the total. The total amount of these glycolipids was 0.59 mg/g of dry weight of the ova preparation, a yield which was one-seventh of that of spermatozoa neutral glycolipids. Structural analyses were performed by enzymatic hydrolysis of the glycolipids with exoglycosidases, permethylation experiments, and also immuno-chemical assays. The proposed structures are as follows: ceramide monosaccharides, Gal-Cer and Glc-Cer; ceramide disacharides, Gal(beta 1-4)Gal-Cer, Gal(beta 1-4)Glc-Cer, and Man(beta 1-4)Glc-Cer; ceramide trisaccharide, Man(alpha 1-3)Man(beta 1-4)Glc-Cer; ceramide tetrasaccharides, Man(alpha 1-3)[Xyl(beta 1-2)]Man(beta 1-4)Glc-Cer, GlcNAc(beta 1-2)Man(alpha 1-3)Man(beta 1-4)Glc-Cer, Man(alpha 1-3)[Gal(beta 1-2)]Man(beta 1-4)Glc-Cer, and Man(alpha 1-2?)Man(alpha 1-3)Man(beta 1-4)Glc-Cer. The latter two ceramide tetrasaccharides were new types of glycosphingolipids. The spectrum of ova glycolipids appeared to be more complicated than that of the spermatozoa glycolipids. The ova glycolipids characterized here, with the exception of ceramide tetrasaccharides, contained considerable amounts of 2-hydroxy fatty acids, which were not observed in the spermatozoa glycolipids. The major sphingosine base was C18-sphingenine in all the ova glycolipids as well as in the spermatozoa glycolipids. However, the content of anteiso type of sphingosine base was 2- to 3-fold higher in the ova than in the spermatozoa.

Stability of tritium-labelled glycosphingolipids

The stability of three tritium-labelled neutral glycosphingolipids (a ceramide monosaccharide, a ceramide disaccharide, and a ceramide tetrasaccharide) having specific activities of 0.2–0.9 mCi/mg were compared over a 2-month period. All were unstable but the instability increased with increased structural complexity. At this activity level, the compounds may be kept for about 1 week with repurification.

Isolation and purification of Le a blood-group active and related glycolipids from human plasma of blood-group A Le a individuals

From 8 1 of human plasma of blood-group A Le a nonsecretors three different Le a blood-group active ceramide pentasaccharides (a total of 4.65 mg) have been isolated, all revealing glucose, galactose, N-acetylglucosamine and fucose in molar ratios of 1 : 2 : 1 : 1 as determined by gas liquid chromatography. A fourth blood-group active fraction (0.72 mg) represents a mixture of a Le a active ceramide pentasaccharide and an A active ceramide hexasaccharide (molar ratio 7.7 : 2.3 as calculated from the content of different aminosugars). Additionally, two different globosides, two different hematosides and a new N-acetylglucosamine containing ceramide tetrasaccharide were obtained. All 9 glycolipid fractions demonstrated homogeneity in analytical high performance thin layer chromatography (HPTLC) using 4 different solvent systems. 0.2 μg of each Le a active glycolipid completely inhibited the agglutination of O Le(a + b −) erythrocytes by 50 μl of 4 hemagglutinating units of caprine anti Le a serum. At least 0.04 μg of each Le a antigen are sufficient for incubation to convert 9 × 10 7 O Le(a−b−) erythrocytes into Le a-positive cells. Mainly due to the relatively low content of the blood-group A glycolipid in plasma (0.17 mg/8 1), previously negative erythrocytes readily become agglutinable by anti Le a sera and not by anti A sera after incubation with appropriate plasma.

Isolation and purification of Lewis blood-group active glycosphingolipids from the plasma of human O Leb individuals.

Eight different glycosphingolipids with four to six sugars per molecule have been isolated from human plasma of blood-group O Leb secretores. Purfication was achieved by preparative highperformance thin-layer chromatography using four different solvent system, by gas-liquid chromatograhical analysis of the sugars as their alditol revealing integral numbers of sugars and by the hemagglutination inhibition test. Two blood-group Lea-active ceramide pentasaccharides (glycolipids 4,5) and three blood-Leb-active ceramide hexasaccharides (glycolipids 6, 7 and 8) were obtained, each revealing glucose, N-acetylglucosamine and fucose in molar rations of 1:2:1:1 (glycolipids 4,5) or 1:2:1:2 (glycolipids 6, 7 and 8) respectively. 0.027 μg of glycolipids 6, 7 and 8 completly inhibited the agglutination of human O Le(a-b+) erythrocytes by 50 μl of 4 hemagglutinating units of caprine anti-Leb sera. Honegeneity of glylipids 6, 7 and 8 was confirmed by the exclusion of contamination of the hypothetical Led antigen being a structural isomer of the Leb antigen: A crude neutral glycolipid fraction enriched in fucolipds from the plasma of O Le(a-b-) secretors showed a high-performance thin-layer chromatographical migration behaviour completely different from that of glycolipids 6, 7 and 8. Glycolipids 4 and 5 exhibited distinct Lea blood-group activities (0.4 μg of glycolipid 4 or 0.6 μ of glycopid 5 per 50 μl of 4 hemagglutinating units of caprine anti-Lea serum), but were slightly contaminated by blood-group H activity or blood-group Leb (7 μg of glycolipid 4/100 μl human anti-H serum and 1.7 μg of glycolipid 5/50 μl caprine anti-Leb serum). 0.01 μg, 0.0006 μg or even only 0.0001 μg of glycolipid 6, 7 or 8 respectively are sufficient for inclubation to convert 9x107 O Le(a-b-) erythrocytes into Lebpositive cells. This means in the case of glycolipid 8. that maximally 400 molecules per erythrocyle on the cell surface are sufficient to acheive an agglutinability by anti-Leb sera. In addition, two different globosides (glycolipids 1, 2) and a new ceramide tetrasaccharide (glycolipid 3) were isolated. The latter substance contains glucose, galactose and N-acetylglucosamine in molar ratios of 1:2:1, but differs from the lacto-N-neotetraosylceramide by showing a distictly slower high-performance thin-layer chromatographical migration behaviour.

Isolation of a novel lipid hapten, cytolipin S, from rat spleen

Antisera against rat erythrocytes contain agglutinins directed against unknown lipid determinants. Complement-fixation shows more reactivity with lipid extracts of rat spleen than of other rat tissues. The isolation of the reactive lipid from rat spleen, cytolipin S, is described. Cytolipin S is a glycosphingolipid containing glucose, galactose, and galactosamine with molar ratios of 1 : 2 : 1. It migrates on TLC like asialo G M1 (more slowly than cytolipin R, a ceramide tetrasaccharide, or cytolipin F, a ceramide pentasaccharide). Asialo G M1 and cytolipin S, when properly combined with auxilliary lipids, react very similarly with anti-rat erythrocyte sera by complement-fixation. However, cytolipin S is much more effective than asialo G M1 in inhibiting the hemagglutination reactions. It is concluded that cytolipin S and asialo G M1 are ceramide tetrasaccharides having different chemical structures and that the structural differences probably will be found in the carbohydrate linkages other than that between the terminal and penultimate residues.

Mass spectrometric analysis of permethylated glycosphingolipids II. Comparative studies on different blood-group active and related erythrocyte membrane glycosphingolipids

Three isomeric ceramide tetrasaccharides — P blood-group active globoside, lacto-N-neotetraosyl ceramide as ABH blood-group precursor, both isolated from human erythrocytes and “asiologanglioside” from human brain as reference standard — and two ceramide pentasaccharides — H blood-group active glycosphingolipid, obtained from blood-group B active ceramide hexasaccharide of human B erythrocytes after α-galactosidase treatment and ceramide pentasaccharide from rabbit erythrocytes with B-like blood-group activity — were investigated by mass spectrometry after permethylation. The carbohydrate moiety exhibits differences not only concerning the sugar sequence but also with regard to the position of some glycosidie linkages: Oligosaccharides containing N-acetylhexosamine substituted at position 4 produce spectra that are distinctly different from those containing C-3 substituted N-acetylhexosamines, thus allowing the differentiation between type 1 and type 2 carbohydrate chains. Moreover, oligosaccharide ions with a hexose at the cleavage site exhibit a fragmentation pattern different from those with a N-acetylhexosamine at the “reducing terminal”. The intensity ratio between parent ion and parent ion — 32 mass units is Q ⩾ 3 in the first case, whereas in the latter case Q is <1. The Q-values are given for 14 oligosaccharide ions. Differences in the composition of the ceramide residues can also be deduced from the mass spectra.

High performance preparative column chromatography of lipids using a new porous silica, iatrobeads® I. Separation of molecular species of sphingoglycolipids

Good preparative separation of neutral glycolipids of human erythrocytes was achieved by column chromatography using the totally porous silica spheres, Iatrobeads®. The solvent flow through the Iatrobeads column was rapid under atmospheric pressure, and so elution bands migrated with minimal diffusion in the column. Ceramide dihexoside and ceramide trihexoside were both separated into two fractions of different molecular species on the Iatrobeads column. Two ceramide tetrasaccharides, globoside I and paragloboside, were also clearly separated on the Iatrobeads column. Chemical analysis showed that separation of these molecular species was due to differences in their fatty acid and long chain base compositions. Sphingadienine and phytosphingosine were found as minor components of long chain bases in human erythrocyte glycolipids.

Surface carbohydrates of hamster fibroblasts. I. Chemical characterization of surface-labeled glycosphingolipids and aspecific ceramide tetrasaccharide for transformants.

1. Neutral glycosphingolipids of hamster fibroblast NIL cells have been characterized as follows: glucosylceramide, lactosylceramide (betaGall yields 4Glc yields Cer), a digalactosylceramide (alphaGall yields 4betaGal yields Cer), a trihexosylceramide (alphaGall yields 4betaGall yields 4Glc yields Cer), two kinds of ceramide tetrasaccharides (A: alphaGa1NAcl yields 3betaGalNAcl yields 3alphaGall yields 4betaGall yields 1Cer, a new type of Forssman active glycolipid; B: globoside, betaGalNAcl yields 3alphaGall yields 4betaGall yields 4betaGlc yields Cer), and a ceramide pentasaccharide having a classical structure for Forssman antigen (alphaGalNAcl yields 3betaGalNAcl yields 3alphaGall yields 4betaGall yields 4Glc yields Cer). 2. Neutral glycosphingolipids of polyoma virus-transformed NIL cells (NILpy) have been characterized as having an additional ceramide tetrasaccharide which was absent in normal NIL cells. The structure of this specific glycolipid was identified as lacto-N-neotetraosylceramide (betaGall yields 4betaGlc-NAcl yields 3betaGall yields 4Glc yields Cer). Chemical quantities of ceramide tetra- and pentasaccharides in NILpy cells were much lower than in NIL cells. 3. All of these glycolipids, except glucosylceramide and lactosylceramide, were labeled externally by galactose oxidase and tritiated borohydride according to the method previously described (GAHMBERG, C. G, and HAKOMORI, S. (1973) J. Biol. Chem. 248, 4311-4317). The specific activities of the label in glycolipid of NIHpy cells were much greater than that in NIL cells, i.e. reactivity of glycolipids with galactose oxidase in NIHpy cells was much higher than for NIL cells. The surface label in glycolipids was cell cycle-dependent in NIL cells, and a remarkable exposure of a galactosyl residue of a ceramide tetrasaccharide was demonstrated only on the surface of NILpy cells, due to the presence of lacto-N-neotetraosylceramide.

Organization of glycolipids and glycoproteins in surface membranes: Dependency on cell cycle and on transformation

Summary Ceramide penta-, tetra-, and trisaccharides of hamster NIL cells were maximally labeled during the G1-phase, and minimally during the S-phase using a surface labeling procedure with galactose oxidase and tritiated borohydride. Since the chemical concentration of ceramide penta- and tetrasaccharides in NIL cells was found nearly constant throughout various phases, the observed change of the label during the cell cycle can be ascribed to the alternation of the exposure rate of glycolipids due to altered organizational assemblage in surface membranes. In polyoma transformed NIL cells, the chemical quantity of higher glycolipids was reduced; nevertheless the rate of exposure was much greater than in NIL cells and was invariant during the cell cycle. There was a unique label in a ceramide tetrasaccharide (“ceramide X”) which was not found in non-transformed NIL cells. The label in “galactoprotein a” of NIL cells appears at the G1-phase and increases at later G1-phases. In transformed NIL cells, this label is always absent, throughout the cell cycle.

Characterization of blood-group-H-active ceramide tetrasaccharide from hog-stomach mucosa.

A fucose‐containing ceramide tetrasaccharide exhibiting blood‐group‐H activity was isolated from a lipid extract of hog stomach mucosa by column fractionations on DEAE‐cellulose and Florisil followed by purification on thin‐layer plates.By partial acid hydrolysis, sequential degradation with specific glycosidases and methylation analysis, the structure of this glycolipid was identified as: Fucα1 →, 2Galα1 → 3Galβ1 → 4Glc1 → 1Cer; where Fuc = fucose; Gal = glucose; Gal = glucose and Cer = ceramide.

A ceramide tetrasaccharide of human erythrocyte membrane reacting with anti-type XIV pneumococcal polysaccharide antiserum

A ceramide tetrasaccharide whose structure was identified as Galβ1→4GlcNAcβ1→3Galβ1→4Glc→ceramide was isolated from human erythrocyte membrane. The glycolipids react with anti-Type XIV pneumococcal polysaccharide antiserum. A ganglioside with an identical carbohydrate skeleton having N- acetylneuraminic acid substituted at the C3 hydroxyl of the terminal galactosyl residue was also characterized.

Structures of ceramide tetrasaccharides from various sources: uniqueness of rat kidney ceramide tetrasaccharide

Methylation analysis of ceramide tetrasaccharide isolated from human erythrocytes gave acetates of 2,3,6-tri-O-methylgalactitol and 2,4,6-tri-O-methylgalactitol in a ratio of 1:1, and about 50% of the galactose was oxidized by periodate. Rat kidney ceramide tetrasaccharide gave, in contrast, a much larger proportion of the acetates of 2,4,6-tri-O-methylgalactitol (ratio 1:0.3), and less than 20% of the galactose was oxidized by periodate. Sequential degradation by beta-N-acetylhexosaminidase, alpha-galactosidase, and beta-galactosidase showed ceramide tetrasaccharides to have identical carbohydrate sequences and anomeric structures. The major part of ceramide trihexoside derived from rat kidney ceramide tetrasaccharide migrated on thin-layer chromatography more slowly than that derived from other ceramide tetrasaccharides. The structure of a major part of rat kidney ceramide tetrasaccharide was thus determined to be GalNAcbeta(1-->3)Galalpha(1-->3)Galbeta(1-->4)Glcbeta(1-->1)Cer, whereas other ceramide tetrasaccharides have Galalpha(1-->4) structure at the penultimate residue.

Immunochemical studies of organ and tumor lipids XVIII. Cytolipin R determinants in the rat erythrocyte membrane

Rabbit antisera to rat lymphosarcoma contain antibodies that agglutinate trypsinized rat erythrocytes. These reactions can be specifically inhibited by cytolipin R, a ceramide tetrasaccharide isolated from rat lymphosarcoma. The agglutinin in the rabbit antisera can be absorbed with untreated erythrocytes, showing that cytolipin R determinants are present in the intact rat erythrocyte membrane. Untreated erythrocytes are able to react with antibody, but presumably the number of cytolipin R determinants necessary for agglutination becomes available only after treatment with trypsin. The anti-cytolipin R antibodies in anti-rat lymphosarcoma sera that cause hemagglutination and those that fix complement with this hapten are different, since the agglutinin can be absorbed completely without appreciable decrease in complement-fixing antibody.