External Labeling of Cell Surface Galactose and Galactosamine in Glycolipid and Glycoprotein of Human Erythrocytes

Changes in the glycoprotein composition of plasma membrane during the differentiation of friend erythroleukemia cells

Friend erythroleukemia cells display transient and permanent changes in the composition of their plasma membrane-bound glycoproteins during dimethyl sulfoxide-induced differentiation. The transient changes, as revealed by metabolic labeling with [14C]glucosamine, are most conspicuous around the time during which most cells become committed to terminal differentiation. Permanent changes are revealed by reductive tritiation after oxidation with NaIO4 or galactose oxidase. In differentiated cells one glycoprotein fraction (Mr 150 000) could not be labeled by any of these methods, although it does contain neuraminic acid. We found no evidence in support of the hypothesis that the anomalous behavior of this fraction is caused by an increased degree of O-acetylated neuraminic acid in the plasma membrane of differentiated cells.

Organization of the glycosphingolipid asialo-GM1 in phosphatidylcholine bilayers

An affinity purified monovalent ferritin conjugate of Ricinus communis agglutinin (RCA 60) is used with freeze-etch electron microscopy to study the ultrastructural localization of the glycosphingolipid asialo-GM1 in multilamellar phosphatidylcholine liposomes. Dimyristoylphosphatidylcholine (DMPC) liposomes containing up to 20 mol% asialo-GM1 and quenched below the main transition temperature show a striking linear localization of ferritin-RCA 60 between phospholipid ridges. The glycosphingolipid localization is similar to that postulated for up to 20 mol% cholesterol in pure phosphatidylcholine bilayers by Copeland, B.R. and McConnell, H.M. (Biochim. Biophys. Acta, 599, 95-109 (1980)). Above the main phase transition temperature, asialo-GM1 appears to be organized into clusters, especially in palmitoyloleoylphosphatidylcholine (POPC) liposomes. This clustered distribution of glycosphingolipids seen above the phase transition temperature suggests that this type of lipid may exhibit compositional domain structure in biological membranes.

Monoclonal antibody to murine embryos defines a stage-specific embryonic antigen expressed on mouse embryos and human teratocarcinoma cells

A murine stage-specific embryonic antigen (SSEA3) is defined by reactivity with a monoclonal antibody prepared by immunization of a rat with 4- to 8-cell-stage mouse embryos. This antigenic determinant, present on oocytes, becomes restricted first to the inner cell mass at the blastocyst stage, and later to the primitive endoderm. Murine teratocarcinoma stem cells do not react with this antibody, whereas human teratocarcinoma stem cells are SSEA3-positive. This antigenic determinant is not expressed on a variety of other human and murine cell lines, but is found on the surface of human erythrocytes. It is a carbohydrate and is present on both cell-surface glycolipids and glycopeptides. These results demonstrate the feasibility of identifying stage-specific antigenic determinants with monoclonal antibody prepared against embryos. The need for thorough screening on a variety of cell types to establish developmentally important cross-reactivities is also emphasized.

Postnatal changes in enzyme activities in synaptosomes isolated from hamster optic nerve endings

Subsynaptosomal fractions isolated from optic terminal nuclei of adult and neonatal hamsters exhibited developmental changes in specific density, mitochondrial activity, and K+-stimulated, ouabain-inhibited p-nitrophenylphosphatase (K-pNPPase) activity around the time of eye opening. The specific activity of K-pNPPase was six- to sevenfold higher after eye opening (14-16 days postnatal). A significant proportion of high-specific- activity K-pNPPase was recovered from the lightest subsynaptosomal fraction at all ages. This fraction contained very little external membrane by galactose oxidase - NaB3H4 labeling, suggesting that it may represent an internal pool, possibly the axonally transported form of the enzyme. Synaptic mitochondrial cytochrome c. oxidase activity also approximately doubled in the period between 12 and 16 days. The specific density of the external membrane increased very slowly, banding at 1.0 M sucrose at 12 and 16 days, and at 1.2 M in adults. These maturational events may reflect increased energetic needs for optic nerve endings following eye opening.

Decreased glycosylation of band 3 and band 4.5 glycoproteins of erythrocyte membrane in congenital dyserythropoietic anaemia type II

We report a study of HEMPAS erythrocyte membrane glycoproteins in relation to proteolytic digestion and surface labelling with galactose-oxidase/NaB[3H]4. The proteolytic digestion of band 3, the major intrinsic glycoprotein of the human erythrocyte membrane, reveals an abnormality in the outer glycosylated segment of this protein. 3H incorporation in band 3 and band 4.5 glycoproteins after treatment with galactose-oxidase/NaB[3H]4 is reduced in HEMPAS red cells suggesting a defective glycosylation of these proteins. These findings together with the persistence of i antigen and the normal presence of I antigen lead us to conclude that erythroblastic membrane features may persist in HEMPAS erythrocytes.

Acute erythroleukaemia with L3 morphology and the 14q+ chromosome

L3 morphology according to the FAB classification and the 14q+ chromosome are usually ascribed to the Burkitt type of leukaemia or lymphoma with a B or pre-B cell phenotype. We report here a case of adult acute leukaemia with Burkitt morphology and the 14q+, which did not express lymphoid markers. Instead, the leukaemia was shown to be an acute erythroleukaemia. The erythrocyte marker glycophorin A was present on the surface of the leukemic blasts as shown by immunofluorescence and immunoprecipitation from membrane lysates of surface labeled cells with antiglycophorin A antiserum. Spectrin and fetal hemoglobin appeared after cultivation of the blasts in the presence of sodium butyrate. The present case shows that a short term cultivation is sometimes useful for further characterization of the commitment of acute leukaemias.

Epstein-Barr virus induced proteins V: comparison of EBV-specific polypeptides from different virus strains

EBV-associated polypeptides induced in different Epstein-Barr Virus (EBV)-producing cell lines by the tumor promotor TPA, and from purified EBV particles derived from the same lines were radioactivity labeled and analyzed by immunoprecipitation with human VCA+MA+ sera. In virus-producing cells no significant differences in the molecular weight of 35S-methionine-labeled EBV-associated polypeptide patterns could be observed. The analysis 125I-labeled polypeptides from purified virus particles of four different strains revealed that, in addition to common polypeptides, individual EBV strains contain strain-specific high molecular weight glycopolypeptides. These polypeptides, constituting part of the membrane antigen complex, are present in varying amounts. While P3HR-1 virus particles contain a major component of 250 000 and small amounts of 340 000 molecular weight polypeptides, Q IMR-WIL virus particles have more 340 00 than 240 000 molecular weight polypeptides. Furthermore, in B95-8 particles and in particles from an EBV strain isolated from an African green monkey (AGM-EBV) respectively, large amounts of 360 000 and 250 000 polypeptides could be observed. Since these glycopolypeptides carry strain-, subgroup- and group-specific antigenic determinants, also found in virus strains produced in human and marmoset cells, it should be further investigated whether these differences in molecular weight are virus-strain- or cell-specific.

Lectin-reactive components in white matter membranes from normal and multiple sclerosis brains

Polypeptides derived from human white matter membranes reacted with the radioiodinated lectins concanavalin A, Lens culinaris phytohemagglutinin, Ricinus communis agglutinin and wheat germ agglutinin after electrophoresis in polyacrylamide pore gradient gels. The molecular weights of these lectin-reactive bands were estimated by comparison with radioiodinated protein standards by using the linear relationship between log of the molecular weight and log of the gel concentration reached by the protein after electrophoresis in a polyacrylamide gradient gel. The molecular weight estimates for components reactive with concanavalin A were 176,800, 141,200, 72,800, 52,800, 44,700, 40,000, 24,800 and 23,900. The molecular weights of the bands reactive with both wheat germ agglutinin and Lens culinaris phytohemagglutinin were 138,000, 113,500, 92,100, 52,800, 44,700, 24,800 and 23,900. Wheat germ agglutinin was bound also to a band with a molecular weight of 72,800. Ricinus communis agglutinin bound to bands with estimated molecular weights of 138,000, 72,800, 52,800, 44,700, 24,800 and 23,900. The electrophoretic pattern of lectin-reactive polypeptides derived from normal-appearing white matter of multiple sclerosis brains was not qualitatively different from the lectin-binding pattern of control brain membrane polypeptides.

Some problems associated with radiolabeling surface antigens on helminth parasites: a brief review

Recent developments in technology have facilitated substantial advances in the characterization of surface antigens from a wide variety of both normal and neoplastic cells. However, the immunochemistry of parasites has lagged behind. Efforts to apply conventional radiolabeling methods to helminths have not always been successful. Experimental work with Schistosoma mansoni is reviewed to illustrate common problems encountered in surface labeling studies. These findings should provide insight for the future investigation of other helminth species.

Role of sialic acid in the mobility of membrane proteins containing O-linked oligosaccharides on polyacrylamide gel electrophoresis in sodium dodecyl sulfate

The major sialoglycoprotein of the human red-cell membrane, glycophorin A, contains 15 O-glycosidically linked oligosaccharides and one N-glycosidic oligosaccharide. The protein shows a decreased mobility on polyacrylamide gel electrophoresis in sodium dodecyl sulfate after neuraminidase treatment of the non-denatured protein. The molecular mechanism behind this phenomenon has been elucidated. Neuraminidase treatment of glycophorin A in intact cells or after solubilization in buffers containing Triton X-100 resulted in conversion of the predominant tetrasaccharide N-acetylneuraminosyl alpha 2-3galactosyl beta 1-3(N-acetylneuraminosyl alpha 2-6)-N-acetylgalactosamine to the trisaccharide galactosyl beta 1-3(N-acetylneuraminosyl alpha 2-6)-N-acetylgalactosamine and the disaccharide galactosyl beta 1-3-N-acetylgalactosamine. After denaturation with sodium dodecyl sulfate, Vibrio cholerae neuraminidase also liberated the N-acetylgalactosamine-bound sialic acids. Such treatment resulted in increased electrophoretic mobility. The results show that distal sialic acids linked to galactose are readily available to neuraminidase, and that their negative charge gives an increased electrophoretic mobility in polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. In contrast, most of the N-acetylgalactosamine-linked sialic acids of glycophorin A are not liberated by neuraminidase without denaturation of the substrate. Like sialic acids of complex-type oligosaccharides the decreased electrophoretic mobility caused by them is exclusively due to their mass while no significant contribution by the charge was seen.

Identification of exposed surface glycoproteins in undifferentiated and differentiated mouse N-18 neuroblastoma cells

A simple method is described that permitted rapid isolation of plasma membranes from mouse N-18 neuroblastoma cells. The purified plasma membranes gave a 10-fold increase in the specific activity of incorporated [3H]fucose over that of the cell homogenate. The specific activities of two other membrane markers, 5'-nucleotidase and alkaline phosphatase, increased 11-fold and 15-fold, respectively. Metabolic labeling with [3H]fucose identified a major fucosyl glycoprotein with apparent molecular weight of 92 000. Three surface labeling methods together with SDS-polyacrylamide gel electrophoresis and fluorography were used to characterize and compare the surface glycoproteins of undifferentiated and differentiated N-18 cells. The galactose oxidase/NaB3H4 method labeled two major galactoproteins (Mr = 52 000, 42 000) in both undifferentiated and differentiated cells. The neuraminidase/galactose oxidase/NaB3H4 method revealed many sialylgalactoproteins. Among them, the 220-kdalton, 150-kdalton and 130-kdalton bands were at least 100% more prominently labeled in the differentiated cells whereas the 76-kdalton and 72-kdalton bands were less prominently labeled in the differentiated cells when compared to their undifferentiated counterparts. The prominently iodinated protein bands in the undifferentiated cells had apparent molecular weights of 130 000, 92 000, 76 000 and 72 000 as compared to 150-, 130-, 92- and 76-kdalton bands in the differentiated cells. The labeling data obtained will enable us to further study the changes of these identified surface glycoproteins, both quantitatively and topologically, during the differentiation of neuroblastoma cells.

Surface components of ejaculated chimpanzee sperm

Surface components of ejaculated chimpanzee sperm were radiolabeled by enzymatic iodination with lactoperoxidase and Na125I. The sperm were lysed and the labeled components analyzed on SDS-7.5% polyacrylamide gels. Electrophoresis of solubilized radioactivity resolved four components with approximate molecular weights of 72,000, 49,000, 25,000 and 17,000 daltons. To identify components, which might be adsorbed to the chimpanzee sperm surface from seminal secretions, seminal plasma was labeled. Electrophoresis of labeled seminal plasma resolved three components with approximate molecular weights of 63,000, 26,000, and 17,000 daltons, two of which comigrated with a labeled sperm surface component.

NK cell-target interactions: approaches towards definition of recognition structures

NK cells lyse an uncommonly wide range of cell types, implying either that they (the NK cells) have clonally distributed receptors each of which is capable of interacting with a very limited number of cell types or, alternatively, that susceptible target cells share a common characteristic. A number of experimental approaches have suggested that the cytotoxic 'specificity' of NK cells is not clonally distributed. Thus, clones of NK cells, established from mouse spleen cell suspensions, showed no greater restriction in the spectrum of target cells which they could lyse, than did the parent spleen cell populations from which they were derived. It seems likely therefore that the wide range of target cell types that can be lysed by NK cells share common cell surface characteristics which render them susceptible. As lysis results from membrane-membrane interactions, it seemed logical that a search for 'hallmarks' of NK susceptibility should begin with a detailed examination of the plasma membrane of susceptible cells. Analysis of one pair of lymphoma cell variants, selected on account of their markedly different susceptibility to NK cells, suggests that cell surface glycoconjugates may be of significance in determining those effector cell-target cell interactions that lead to lysis. This review outlines attempts to characterize such glycoconjugates.

Chronic lymphocytic leukemia: demonstration of cell surface structural heterogeneity by lectin affinity chromatography of cell extracts

I have used lectin affinity chromatography of radiolabelled components in cell extracts to examine molecular heterogeneity of membrane glycoproteins from 10 cases of chronic lymphocytic leukemia (CLL). Different complements of radiolabelled surface glycoproteins were found in extracts from cells with different lectin binding characteristics. Additional confirmation of heterogeneity was obtained by analyses of hexose and sialic acid contents of the extracts and various lectin-adherent fractions. The fact that CLL cells from different patients may carry different cell surface oligosaccharides provides the possibility that clinical variability in this disorder may relate in part to this molecular heterogeneity. The data further indicate that different lectins may bind to different saccharide structures at CLL cell surfaces. CLL cells represent excellent source material for isolation and purification of specific lectin receptor molecules.

Surface membrane proteins and glycoproteins of red blood cells from normal and anaemic mice

1. The surface membrane proteins of red blood cells from normal, hyperbled or acetylphenylhydrazine-treated BALB/c mice and NZB mice of different ages were labelled by lactoperoxidase-catalyzed radioiodination. Sialoglyoproteins were labelled by periodate/NaB3H4 or galactose oxidase +/- neuraminidase/Na3H4 treatments. 2. Anaemia produced several changes in radioiodinated proteins. 3. Sialoglycoprotein radiolabelling was unchanged, even with over 90% reticulocytosis. 4. Decreased periodate/NaB3H4-dependent labelling of red blood cells from Plasmodium berghei-infected BALB/c mice (Howard et al., 1980; Howard & Day, 1981) cannot therefore be due to anaemia per se, but must be related more specifically with infection.

Growth of human malaria parasites in biotinylated erythrocytes

The adaptation of the biotin-avidin system for the analysis of membrane pathobiology in Plasmodium falciparum malaria is described. Biotin was linked covalently via the succinimide ester derivative (biotinyl-N-hydroxysuccinimide ester, BNHS) to intact human erythrocytes, prior to inoculation and in vitro cultivation of falciparum parasites. Growth experiments indicated that incubation concentrations of less than 1.0 mg BNHS/1.0 ml erythrocyte packed cell volume could yield biotinylated erythrocytes capable of sustaining parasite growth at levels comparable to control cultures. Using a synthesized [14C]BNHS compound at optimal incubation concentration, it was determined that 1.32 X 10(-4) mmol [14C]BNHS were bound per 1.0 mg of erythrocyte stromal protein. In addition, analysis of [14C]biotinylated red blood cell ghost preparations by polyacrylamide gel electrophoresis demonstrated that band 3 (a heterogeneous glycoprotein) was the principal site of membrane labeling. Approximately 77% of total membrane-associated [14C]BNHS was localized to this polypeptide. The unique properties of the specific, ligand-protein interaction of the biotin-avidin complex suggest that the biotinylation procedure described in this report will provide a useful analytical tool in host cell-plasmodial parasite, membrane studies.

Surface protein abnormalities in lymphocytes and platelets from patients with Wiskott-Aldrich syndrome

Lymphocytes from three patients with the Wiskott-Aldrich syndrome were subjected to surface radioiodination and their 125I-labelled surface proteins were analysed by SDS-polyacrylamide gel electrophoresis and autoradiography. Autoradiographs demonstrated the absence in all three patients of an 125I-labelled protein, molecular weight of 115 000, that was present in normal individuals. In addition, one patient had an additional labelled protein, molecular weight 135 000, not found in normal individuals. The platelets from one patient were radioiodinated and the 125I-labelled membrane proteins were analysed. Glycoproteins Ia and Ib were reduced in amount and restricted in heterogeneity while glycoproteins IIb and IIIa were normal. These results suggest that the primary defect in the Wiskott-Aldrich syndrome may be abnormalities of (glyco)proteins normally present on the surface of lymphocytes and platelets.

Alterations in labeling of cell-surface glycoproteins from normal and diabetic rat intestinal microvillous membranes

The effect of chronic streptozotocin-induced diabetes was studied on intestinal microvillous membrane surface carbohydrate groups. After 7 weeks of diabetes, purified microvillous membranes were prepared from rat small intestine and surface galactoproteins identified by labeling with galactose oxidase/sodium boro[3H]hydride. Membrane surface sialic acid residues were labeled using the sodium metaperiodate/sodium boro[3H]hydride technique. Membranes were solubilized in SDS and protein labeling analyzed by acrylamide electrophoresis. Membranes from diabetic rats showed an 81% increase in galactoprotein labeling (P less than 0.02) while labeling of sialic acid residues was unchanged. The greatest increase in galactoprotein labeling occurred in protein monomers of Mr 116,000-200,000, where there was a 155% increase in labeling (P less than 0.005). These results indicate that intestinal microvillous membrane protein glycosylation is altered in chronic diabetes. This increase in surface membrane carbohydrates could explain the decreased rates of proteolytic degradation previously described for at least one microvillous protein. An increase in membrane galactose groups has also been noted in hepatocyte and kidney glomerular basement membranes, which suggests the presence of a systematic change in membrane protein glycosylation occurring as a result of the diabetic state.

The organization of gangliosides and other lipid components in synaptosomal plasma membranes and modifying effects of calcium ion

Synaptosomes were prepared from bovine brain by zonal rotor sucrose density centrifugation. While a major fraction of lipid-bound sialic acid is included uniformly within the synaptosomal distribution profile, the sialoglycoproteins and some gangliosides do not follow this pattern. Exposure to extrasynaptosomal calcium results in alterations in the surface labeling properties of some gangliosides and membrane plasmalogens, suggesting that extrasynaptic Ca2+ may influence the conformation of complex lipids in synaptic plasma membranes. The level of intrinsic membrane-associated sialidase activity that liberates sialic acid from these sialoglycoconjugates parallels the synaptosomal buoyant density distribution profile, supporting a view that this enzyme resides in synaptosomal membranes in close association with a sialolipid substrate.

Glycoproteins containing peanut-agglutinin receptors from human-peripheral-blood T-lymphocyte plasma membranes

A glycoprotein fraction possessing peanut agglutinin receptors has been isolated from detergent extracts of neuraminidase-treated human peripheral blood T-lymphocyte plasma membranes with affinity matrices comprising the peanut agglutinin co-valently immobilised on Sepharose 4B. This fraction could be specifically eluted from affinity columns using buffer solutions supplemented with 0.2 M D-galactose and was shown, by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (0.1%), to contain four major glycoprotein components with apparent molecular weights of 200000, 190000, 110000 and 95000. It is suggested, from the observed reactivity of these glycoproteins with various lectins in double-diffusion experiments, that they possess both O-glycosidically and N-glycosidically linked carbohydrates.

The measles virus-specific protein synthesis of persistently and lytically infected cells studied in vivo and in vitro

The virus-specific protein synthesis of the hamster brain cells persistently infected with a wild-type measles virus (M-MB/MVB) was investigated in vivo and in vitro and compared to the protein synthesis of the Vero-cells lytically infected with the wild-type measles virus and the SSPE-measles virus strain LEC. The virus-specific protein synthesis in the M-HB/MVB-cells in vivo was weak. Only two virus-specific polypeptides, corresponding to polypeptide G and nucleocapsid polypeptide NP, were detected. On the other hand, the in vitro translation products, coded by the RNA extracted from the actinomycin D-treated M-HB/MVB-cells, were similar compared to those products coded by the RNAs from the lytically infected Vero-cells. The polypeptides with MWs of 75 000, 61 000, 40 000, 37 000 and 18 000 were coded with all three RNA-extracts. So the similar mRNAs were induced in the actinomycin D-treated M-HB/MVB-cells, but their translation in vivo was limited. In addition to those polypeptides mentioned above the polypeptide with a MW of 42 000 was detected among the in vitro translation products of the M-HB/MVB-cells.

Identification of liver cell membrane galactoglycoproteins involved in the process of insulin binding

The glycoproteinic nature of the insulin receptor was indicated using two different approaches: 1. [125I] insulin binding to soluble receptors from mouse liver was inhibited by digestion with beta-galactosidase or pretreatment with Ricinus communis I or concanavalin A. An other enzyme (neuraminidase) and lectins (wheat germ agglutinin, Dolichos biflorus) did not affect the binding reaction. These data confirmed that insulin directly interacts with the galactoglycoproteins of liver membranes. 2. The galactose oxidase-sodium boro[3H] hydride technique, previously used for labeling accessible membrane galactoglycoproteins, was again utilized to discern the components that interact with insulin. When liver membranes were equilibrated with 10-7 M insulin prior to labeling, the SDS gel radioactive profiles were specifically modified with two galactoglycoprotein of apparent molecular sizes 195 000 and 145 000, compatible with their participation in the insulin binding interaction. Membrane pretreatment with beta-galactosidase or Sophora japonica lectin reduced the labeling in most peaks, thus supporting the argument for labeling sensitivity. Preincubation of membranes with 10-7 M proinsulin slightly hindered labeling, while pretreatment with 10-7 M glucagon was ineffective, suggesting a specificity of the insulin effect. These data indicate that glycoprotein nature of the insulin receptor for two reasons: alteration of insulin binding after modification of the galactoglycoproteins, and alteration of galactoglycoprotein labeling after insulin binding. Two galactoglycoproteins, with apparent molecular weights 145 000 and 195 000, respectively, were identified and they are suggested to have insulin binding properties.

Studies on malaria in Papua New Guinea: comparison of the surface glycoproteins on red blood cells from infected and uninfected individuals

The levels of erythrocyte membrane sialic acid from 17 patients with Plasmodium falciparum malaria and 1 with Plasmodium vivax malaria, in Papua New Guinea, have been compared with 9 uninfected controls. The amounts of radioactivity incorporated into the major erythrocyte glycoproteins by the periodate/NaB3H4 or galactose oxidase plus neuraminidase/NaB3H4 methods were unchanged by malaria infection. The electrophoretic mobilities of these proteins also were unaffected. Several new glycoprotein bands with molecular weights (mol. wt) of 160,000, 89,000, 46,000, 42,000 and 33,000 Daltons were labelled on the surface of erythrocytes from infected individuals; however, none of these bands appeared in all malarious samples. Sialic acid levels on the erythrocyte membrane were also measured by exhaustive neuraminidase treatment and quantitative assay of released sialic acid. The amount of sialic acid was raised in 1 infected individual, within the normal range for Europeans in 4 others, and below this range with 3 patients. Apparently, extensive removal or modification of sialic acid on the surface of uninfected erythrocytes does not occur in human malaria, in contrast to the results obtained in earlier studies with the lethal murine malarias.

Surface antigens of human melanoma cells defined by monoclonal antibodies. I. Biochemical characterization of two antigens found on cell lines and fresh tumors of diverse tissue origin

Monoclonal antibodies were produced against melanoma cell lines derived from patients presently disease free. Based on tissue distribution of binding, the antibodies obtained could be used to classify melanoma surface antigens into groupings similar to those obtained from studies of autologous and xenogeneic antibodies. Three antibodies (21.43, 15.75 and 15.95) reacted with the immunizing tumor but not with peripheral blood lymphocytes or a lymphoblastoid cell line derived from the tumor donor. When tested on a broader cell panel, antibody 21.43 reacted only with melanoma lines, while antibodies 15.75 and 15.95 reacted with carcinoma cell lines as well as with the majority of melanoma cell lines. Antibody 15.95 precipitated a 49000 dalton glycoprotein from both melanoma and carcinoma cells. Antibody 15.75 precipitated a 74000 dalton glycoprotein from the surface of melanoma and carcinoma cell lines which is also found on freshly isolated tumor cells from melanoma and carcinoma metastases in vivo.

In vivo ageing of human erythrocytes and cell-surface labeling by D-galactose oxidase and sodium borotritide

Young and old, human erythrocytes, separated in vitro according to their age in vivo, were radioactively labeled at the cell-surface D-galactosyl and 2-acetamido-2-deoxy-D-galactosyl residues by treatment with D-galactose oxidase, followed by reduction with sodium borotritide. The labeling was quantitatively determined for each type of erythrocyte by measuring the molar amounts of borohydride necessary for the complete reduction of the oxidized residues. The number of surface residues per blood-group A+ erythrocyte was found to be 37.6 +/- 1.8 x 10(6) (n = 8) for young, 21.8 +/- 4.9 x 10(6) (n = 8) for old, and 24.8 +/- 6.4 x 10(6) (n = 8) for middle-aged erythrocytes, indicating a significant decrease of the residues during ageing.

Human cell lines express multiple populations of Ia-like molecules

Three monoclonal antibodies have been used to isolate Ia-like antigens from three human cell lines; two of which are thought to be homozygous at the HLA-D/DR locus. Complete extraction of the Ia antigens identified by one antibody leaves those recognized by the two remaining antibodies in three parallel sets of experiments, indicating that the antigenic determinants recognized by these antibodies are present on three different populations of Ia molecules from cells of single individuals. These three populations of Ia-like molecules may reflect serologic variants of the product of a single genetic locus or may represent the products of as many as three nonallelic genetic regions. Demonstration of the existence of these multiple populations of Ia-like molecules on presumed homozygous typing cells indicates that this antigenic system is much more complex than has been generally realized. Further study may clarify the relationship between HLA-D/DR type and susceptibility to a variety of diseases and ultimately lead to better matches and improved survival for allogenic transplants. Since the HLA-D region is intimately involved in regulation of the immune response and susceptibility to a variety of diseases, use of monoclonal antibodies specific for discrete Ia antigens, the only identified products of the HLA-D region, may facilitate dissection of its many biological functions.

Interferon induces an antiviral state in ganglioside-deficient transformed mouse fibroblasts

The antiviral activity of mouse fibroblast interferon against vesicular stomatitis virus was investigated in L-929 mouse fibroblasts and the ganglioside-deficient L-929 mutant cells (ATCC clone NCTC 2071). Although it has been widely reported that gangliosides serve as primary receptors for interferon at the cellular membrane, only a small difference in interferon sensitivity was observed between the wild-type L-929 and the ganglioside-deficient NCTC 2071 cells. It was not possible, however, to overcome this difference by administration of exogenous gangliosides.