Suppression of the polyclonal B-cell responses by concanavalin A-treated bone marrow B cells in vitro

A suppressor cell that inhibits the development of a polyclonal antibody response of splenic B cells to lipopolysaccharide is generated in the bone marrow cell culture in response to a mitotic dose (10 micrograms/ml) of concanavalin A (Con A). The Con A-responding suppressor cell is radioresistant and found in a bone marrow B (BM-B) cell population of normal as well as athymic mice. The suppressor activity of Con A-treated BM-B cells was consistently higher (P less than 0.01-0.0001) than those of untreated BM-B and fresh BM cells. The BM-B cell population recovered from short-term (3-day) cultures with Con A contained about 65% surface immunoglobulin (Ig)-positive cells, about 6% T cells, and less than 0.5% plastic-adherent cells, the latter two of which did not contribute to the suppressive activity. Thus, cytolytic treatment with various anti-T-cell antibodies could not eliminate the suppressive activity of the Con A-treated BM-B cells, and the Con A-treated macrophage population provided no significant suppression. The Con A-treated BM-B cells adherent to anti-Ig or anti-Con A dishes exhibited highly enriched suppressive activity. It was therefore concluded that an immature B-cell population of bone marrow could develop in response to stimulation with Con A into surface Ig-positive suppressor cells, contributing to the regulation of nonspecific B-cell responses.     

Use of lectins as probes for analyzing embryonic induction

Summary Lectins were used as probes to investigate the mechanism of embryonic induction. Concanavalin (Con A) and gorse agglutinin out of 7 species of lectins tested were found to have strong neural-inducing effect on the presumptive ectoderm of newt gastrulae. Their effects were abolished by the addition of -methyl-D-mannoside and -L-fucose, respectively. Succinyl-Con A had a weak inducing activity in comparison to Con A. Autoradiography of³H-Con A-treated explants revealed that Con A bound to the inner surface, but not to the outer surface of ectoderm and was successively incorporated into cytoplasm.³H-Thymidine incorporation was lower in the first half and higher in the second half of the 60 h cultivation period in Con A-treated explants as compared to controls.Con A-Sepharose had a strong inductive effect. This suggests that neural induction is caused through Con A binding to the plasma membrane, but not through incorporation into the cytoplasm of the ectoderm cells.     

Polar effects of concanavalin A on the cortical cytoskeleton of a molluscan egg (Nassarius reticulatus,Gastropoda)

Summary The organization of the surface of fertilizedNassarius reticulatus eggs was probed by investigating the effects of treatment with concanavalin A (Con A). This lectin causes abnormal polar lobe formation as well as inhibition of cleavage. At low concentrations of Con A (0.3–1.0 μg/ml) the polar lobe constriction becomes considerably elongated, whereas at higher concentrations (2.5–50 μ/ml) the position of the constriction undergoes an extreme shift towards the animal pole. In the latter case, the surface of the animal part of the egg forms large protrusions and folds. Con A also causes resorption of microvilli and disappearance of the extracellular layer covering these villi; this process starts at the vegetal pole and propagates towards the animal pole. These changes in surface architecture are associated with profound changes in the organization of filamentous (F-) actin as assessed by confocal laser scanning microscopy of NBD-phallacidin-labelled eggs. Divalent succinyl-Con A has the same effects on polar lobe formation and surface architecture as tetravalent Con A, but only at very high concentrations (100–200 μg/ml), indicating that Con A exerts its effects by cross-linkage of its binding sites. Experiments with cytoskeleton inhibitors (cytochalasin D, colchicine, and nocodazole) reveal that in Con A-treated eggs — as in untreated eggs — microfilaments, but not microtubules, are involved in the formation of the polar lobe constriction. The calcium ion channel blocker D600 affects neither normal nor Con A-induced abnormal polar lobe formation, which suggests that influx of external calcium is not required. In contrast, treatment with TMB-8, an antagonist of internal calcium release, prevents the formation of a polar lobe in both normal and Con A-treated eggs. Finally, eggs from which the polar lobe has been removed prior to Con A treatment show none of the effects described, whereas isolated polar lobes react similarly to intact eggs. These results suggest that binding of Con A to sites present at the vegetal pole of the egg is responsible for the observed effects of the lectin.     

Glycoproteins responsive to the neural-inducing effect of Concanavalin A in Cynops presumptive ectoderm

To examine the possible occurrence of receptors in the ectodermal cell surface which apparently mediates the neural-inducing stimulus, a further experiment by using Con A was done in combination with the enzyme treatments. The presumptive ectoderm explants of Cynops gastrula were first treated with neuraminidase to remove sialic acid. Prior to the Con A treatment, the explants were treated with almond glycopeptidase, which cleaves the asparagine linkage between protein and oligosaccharide in glycoprotein and releases the oligosaccharide moiety intact containing mannose residue from the substrate. No neural induction occurred. When the explants were not treated with almond glycopeptidase, the neural induction frequency was found to be the same as that of the explants treated with only Con A. Biochemical analyses showed that when the fixed ectoderm explants were treated with almond glycopeptidase, several oligosaccharides were released and then fractionated by means of Bio-Gel P-4 filtration. Based on the strict specificity of almond glycopeptidase, these oligosaccharides are unmistakably asparagine-linked oligasaccharides with mannose residues. We discuss the hypothesis of involvement of glycoproteins in the first step of molecular events in the neural induction mechanism.     

Concanavalin A induces neural tissue and cartilage in amphibian early gastrula ectoderm

We have studied in vitro differentiation of explants of the amphibian (Rana temporaria) early gastrula ectoderm after treatment with various concentrations (50–300 μg/ml) of ‘free’ and Sepharose-bound concanavalin A (Con A). The explants were incubated with Con A for 3 h at 20°C; the rolling up of the explants was prevented by using special weights. We have demonstrated that: (1) free Con A has an inducing action on the explants in the concentration range 100–300 μg/ml medium; (2) when treated with Con A the explants produce neural tissue (50–70%), cartilage (20–40%) and, rarely, lentoids (5–10%); (3) the frequency of neural and cartilage inductions was similar at various Con A concentrations; (4) α-methyl-d-mannoside pyranoside inhibited the Con A effects; (5) Sepharose-bound Con A had no effect on the explants, although it was bound to the cell surface of the ectoderm inner layer. Possible mechanisms of the neuralizing and chondrogenic effects of Con A on ectodermal explants are discussed.     

Concanavalin A inhibition of alpha-bungarotoxin binding to a nonfusing muscle cell line.

Incubation of a nonfusing muscle cell line, BC3H1, with concanavalin A (Con A) results in a maximum decrease of 35% in the cell's ability to bind alpha-bungarotoxin (alpha-BuTx). The Con A-induced inhibition of 125I-alpha-BuTx binding is reversible and the degree of inhibition parallels the degree of saturation of Con A binding sites on the cell surface. The maximum level of Con A-induced inhibition of 125I-alpha-BuTx binding is not affected by increasing the time of incubation in Con A, using higher concentrations of Con A or by increasing the time of incubation in the presence of 125I-alpha-BuTx. In addition, all BC3H1 cells in culture are sensitive to the Con A-induced inhibition of 125I-alpha-BuTx binding. A comparison of the pseudo-first order rate constants for 125I-alpha-BuTx binding to untreated (8.6 x 10(4) M-1 S-1) and Con A-treated (5.4 x 10(4) M-1 S-1) BC3H1 cells, however, shows that those acetylcholine receptors in Con A-treated cells which bind 125I-alpha-BuTx do so with a lowered apparent affinity. Partial inhibition of toxin-binding capacity is not a consequence of two classes of acetylcholine receptors on the cell surface. Furthermore, individual receptors experience partial inhibition of their binding capacity by Con A, resulting in receptors with at least one binding site blocked and at least one site available for alpha-BuTx binding.     

Concanavalin A Acts as a Factor in Establishing the Dorso-Ventral Gradient in the Ventral Mesoderm of Newt Gastrula Embryos1

Con A induced dorsal differentiation in the ventral mesoderm of Cynops gastrula embryo. This process apparently requires a certain amount of Con A to be internalized as supported by the following evidence: 1) Oligomannose-type oligosaccharide, a potent inhibitor of Con A, considerably inhibited dorsalization of ventral mesoderm by Con A. The incorporation of ¹²⁵I-Con A into the ventral mesoderm was greatly inhibited by this sugar. 2) Sepharose-immobilized Con A did not dorsalize the ventral mesoderm. Con A-induced dorsalization was found to be concentration-dependent. Microautoradiograms of ¹²⁵I-Con A-treated ventral mesoderm suggest that the target site (some receptor molecules) of Con A exists inside the cell. Con A is the first pure substance reported to mimic the two properties of the organizer—neural induction of the competent ectoderm and dorsalization of the ventral mesoderm. In neural induction, Con A acts on the cell surface, while Con A apparently needs to be internalized to trigger dorsal differentiation. Interestingly, Con A-dorsalized ventral mesoderm acquired the neural inducing function of the organizer within the early phase of dorsalization.     

Divergent actions of monomeric, dimeric, and tetrameric concanavalin A on lymphocyte traffic

The autoradiographic analysis of the localization of [³H]adenosine-labeled cells exposed to concanavalin A (Con A) in vitro has confirmed that the altered migration of Con A-treated lymphocytes is a consequence of their slower rate of migration and delay in normal areas of traffic (5, 6). The mechanisms through which Con A alters cell migration were further investigated by studying the effects of several derivatives of Con A on the distribution of ⁵¹Cr-labeled lymph node cells. The results obtained show that the monomeric and dimeric forms of Con A were unable to modify cell traffic, a condition that was partially reversed when succinyl Con A-treated cells were exposed to divalent antibodies to Con A. This suggests that Con A may alter lymphocyte recirculation by actively modifying the membrane fluidity or the surface lateral transport of the lymphocyte. Whatever the exact mechanisms responsible for the altered migration are, they probably involve complex active processes that can be related to the heterogeneity of Con A receptors, the existence of subsets of cells with different reactivities to the lectin, or simply the result of a passive phenomenon dependent on the presence of Con A on the cell surface.     

Characteristics and mechanisms of action of the concanavalin A-activated suppressor cell in man.

Human peripheral blood lymphocytes treated for 24 to 48 hr with optimally mitogenic doses of concanavalin A suppressed the proliferative response of autologous T cells to mitogens and antigens. Con A-treated cells also suppressed the proliferative response and the immunoglobulin synthetic response of autologous B cells stimulated in vitro by T cell helper factor. The human Con A suppressor cell was sensitive to treatment with mitomycin C and to exposure to radiation doses exceeding 1000 rads. The Con A suppressor cell was shown to reside in the nylon wool-nonadherent, sheep red cell rosette-forming, histamine receptor-bearing population of lymphocytes and to lack surface DRW antigens. One mechanism of action of Con A suppressor cells was shown to be the inactivation of nonspecific T cell helper factor.     

Cell-to-substratum adhesion of dissociated embryonic cells of the sea urchin,Pseudocentrotus depressus

Summary Some plant lectins, Concanavalin agglutinin (Con A), succinyl Con A and wheat germ agglutinin (WGA) increased the adhesion of dissociated embryonic cells of the sea urchin,Pseudocentrotus depressus, to the substratum (plastic and glass surface) in vitro. Other plant lectins,Ulex europeus agglutinin (UEA) andDolichos biflorus agglutinin (DBA) had no effect on the cell-to-substratum interaction. A specific monocarbohydrate inhibitor of lectins, -methyl-d-mannoside, inhibited the Con A-induced cell-to-substratum adhesion of dissociated embryonic cells. This observation suggests that the Con A-induced cell-to-substratum adhesion may be attributed to the Con A-carbohydrate interaction. In Millipore-filtered sea water (MPFSW) containing Con A (0.1 mg/ml), dissociated embryonic cells adhered to the substratum for more than 6 h at 18°C, while in MPFSW as control, almost all the dissociated cells were released from the substratum after 1 h. A scanning electron microscopic study showed that dissociated embryonic cells adhered to the substratum were surrounded by an extracellular fibrous material, when the cells were cultured in MPFSW containing Con A. The induction of the extracellular fibrous material by Con A was inhibited by -methyl-d-mannoside. The appearance of this material may be related to the cell-to-substratum adhesion of dissociated cells. Sequential extractions of Con A-treated dissociated cells with Triton X 100 and urea solubilized most of the cellular components, leaving the fibrous material on the surface. Biochemical conponents of the isolated fibrous material included sea urchin fibronectin, Con A and minor components (88 and 140 kilodalton proteins). Fibronectin preformed in the cells was excreted after the dissociation, while the 88 and 140 kilodalton proteins were synthesized and released to the extracellular space.     

A study of the mechanism of Con A-induced immunosuppression in vivo

The plaque-forming cell (PFC) response to sheep erythrocytes (SRBC) is suppressed in a dose-related manner when concanavalin A (Con A) is administered intravenously to mice prior to or after immunization with antigen. The magnitude of suppression as well as the duration of the Con A effect greatly depends on the concentration of antigen used for immunization. Although profound suppression of the anti-SRBC PFC response is observed in intact mice pretreated with Con A for 4-24 hr, spleen cells from these mice do not exhibit suppressive activity when transferred into normal recipients or when cotransferred with normal spleen cells into irradiated recipients. Moreover, the cells from Con A-treated mice respond as normal spleen cells to SRBC when transferred alone into irradiated hosts. Suppression of the anti-SRBC PFC is only observed when adoptive hosts of cells from Con A-treated mice are also injected with Con A within 48 hr (but not 72 hr) of cell transfer and immunization. This time course of responsiveness to the suppressive effects of Con A is similar to that observed in normal mice and in irradiated recipients of normal spleen cells. The immune response to SRBC is also suppressed in adoptive hosts of normal spleen cells that are pretreated with Con A 4-24 hr prior to irradiation and cell transfer. Although functionally inactive when transferred into adoptive hosts, spleen cells from mice pretreated with Con A for 4-24 hr can suppress a primary antibody response to SRBC in vitro. The suppressive activity, which cannot be detected in the spleens of mice when the interval between pretreatment and assay is longer than 24 hr, is present in a subpopulation that bears the Thy 1.2 and Lyt 2 phenotype. Taken together the results obtained in in vivo and in vitro functional assays suggest that a suppressor cell population is activated following in vivo treatment with Con A, but that the cells rapidly lose their state of activation when removed from a Con A environment. This phenomenon is in all probability responsible for the failure to demonstrate suppressive activity in the spleens of Con A-treated mice using in vivo functional assays.     

Induction of blood cells in Xenopus embryo explants

 A Xenopus-specific anti-leukocyte monoclonal antibody designated XL-2 was isolated and used to identify leukocytes in tailbud embryos and activin A-treated explants of blastula animal cap. XL-2 bound to a 135-kDa polypeptide in western blots of protein extracts from adult thymocytes, tailbud embryos, tadpoles, and explants. In cell suspensions, it immunostained the cell surface of all types of adult leukocytes including lymphocytes, monocyte/macrophages, thrombocytes, and granulocytes. At embryonic stage 24, immunocytochemistry revealed XL-2-positive leukocytes, the earliest time at which such cells have been recognized. Whole-mount staining of tailbud embryos and tadpoles showed a widely dispersed population of XL-2-reactive leukocytes, many of which had elongated shapes and ameboid pseudopodia. In activin A-treated animal caps, XL-2 recognized a subpopulation of cells within the lumen of the central fluid-filled cavity as well as cells in the interstitium of mesenchymal and mesothelial components of the explant. Together, activin A and human interleukin-11 induced 100% of explants to form lumenal blood cells. Compared to activin A alone, murine stem cell factor plus activin A significantly increased the numbers of XL-2-reactive leukocytes and erythrocytes. These results support the view that activin A induces leukocyte and erythrocyte progenitors during Xenopus embryogenesis. Received: 29 August 1997 / Accepted: 28 October 1997     

Electron microscope study of the binding of Con A-gold to superficial and inner ectoderm layers ofXenopus laevis and its relation to the neural-inducing activity of this lectin

Summary Isolated competent amphibian ectoderm differentiates into neural (archencephalic) structures when treated with the plant lectin concanavalin A (Con A). While the inner ectoderm layer ofXenopus laevis forms brain structures after incubation with Con A, the outer ectoderm layer differentiates into ciliated epidermis only. This difference can be correlated with the pattern of Con A bound to the plasma membrane. With gold-labelled Con A it could be shown by transmission electron microscopy (TEM) that the outer ectoderm binds substantially less lectin than the inner layer. Furthermore we observed characteristic differences at the apical and basal surfaces of the cells of the same layer, i.e. on the apical cell surface of the superficial layer almost no Con A-gold could be found. In contrast, we observed a lot of gold particles on the basal cell side of the superficial layer. However, the number on both surfaces (apical and basal side of the cell) of the inner ectoderm layer was essentially higher, which could explain its biological reaction to the Con A stimulus and the differentiation into neural structures. The data presented in this paper indicate that early and late gastrula ectoderm bind similar amounts of Con A and support the view that the decrease in competence is not correlated with a loss of receptors for inducing factors. Furthermore, we describe the binding and the internalization of Con A via receptor-mediated endocytosis and the further fate of the Con A-gold-receptor complex inside the target cell.     

Concanavalin A inhibition of ecto-5'-nucleotidase of intact cultured C6 glioma cells.

A pronounced effect of concanavalin A (Con A) upon activity of ecto-5'-nucleotidase of intact C6 glioma cells in culture has been demonstrated. A near linear rate of decrease in 5'-nucleotidase activity was observed upon treatment with concentrations of Con A up to 0.25 muM. Nonspecific phosphatase activity and Ca2+-dependent ATPase activity were not inhibited by Con A treatment of the cells. Of the total 5'-nucleotidase activity of C6 cells (Vmax = 5.0 mumol of Pi liberated/mg of cell protein/hour), approximately 20% still remained after treatment with high concentrations of Con A. The inhibitory effect of Con A operated to reduce substantially Vmax for ecto-5'-nucleotidase. Inhibition was reversed by briefly incubating the Con A-treated cells with alpha-methyl-D-glucoside, or alpha-methyl-D-mannoside, the later being more effective. These findings suggest that a relatively specific, reversible, inhibition of ecto-5'-nucleotidase results from Con A binding to the surface of the intact cultured mammalian cells.     

Forskolin and cyclic adenosine monophosphate inhibit the neurulation action of concanavalin A on explants of the gastrula ectoderm of amphibians]

We studied effects of forskolin, an activator of adenylate cyclase activity, and dioctanoyl-cyclic adenosine monophosphate (do-cAMP) on neutralizing (N) activity of concanavalin A (Con A). Biological testing was performed using explanted animal pole ectoderm of the Rana temporaria early gastrula. Con A treatment (200 micrograms/ml, 2 h) resulted in neutralization of 70-90% explants. If the explants were previously treated with forskolin (100 microM, 1 h), Con A effect decreased to 10%. When Con A and forskolin were applied simultaneously, no N-effect was observed. The same results were obtained with simultaneous treatment of the explants with Con A and do-cAMP (10(-5) M). Moreover, treatment with forskolin of the explants previously treated with Con A inhibited their neural differentiation. We suggest that N-effect of Con A is calcium dependent; the increase in intracellular cAMP after treatment of explants with forskolin or do-cAMP interferes with intracellular Ca2+ release and this results in the inhibited N-effect of Con A.     

Divergent effects of cyclosporine A on interferon- and mitogen-induced Ly-6A antigen suggest autocrine regulation of Ly-6A expression in activated T cells

The murine Ly-6A cell surface antigen is normally present on a minor subset of mature T cells. This marker has been shown to become highly expressed on mitogen-activated T cells. We found that expression of Ly-6A is also markedly increased in resting T cells by incubation with IFN-alpha/beta or IFN-gamma. Here, we compared the effect of the immunosuppressant cyclosporine A (CsA) on Ly-6A induction by IFN and concanavalin A (Con A). The augmentation of Ly-6A expression produced by treatment of T cells with IFN-alpha/beta or IFN-gamma was found not to be affected by CsA concentrations up to 2 micrograms/ml. In contrast, at doses as low as 50 ng/ml, CsA prevented the enhancement of Ly-6A expression in Con A-treated T-cell cultures. Culture supernatant transfer experiments were performed to further explore this effect of CsA. It was found that supernatants from Con A-activated T cells enhanced Ly-6A expression in resting T cells. This activity could be neutralized with an anti-IFN-gamma monoclonal antibody. Supernatants from T cells treated with Con A in presence of CsA lacked Ly-6A-enhancing activity. Taken together, these data suggest that the inhibition by CsA of Ly-6A induction in Con A-treated T cells reflects the known inhibitory effects of the drug on IFN-gamma secretion. This may imply the existence in T cells of an autocrine circuit involving IFN-gamma and regulating Ly-6A expression.     

Modification of Drosophila cell surfaces by concanavalin A

Summary The effect of Con A on the surface morphology of cultured cells of Drosophilia melanogaster growing on coverglasses was examined by scanning electron microscopy. With low lectin concentrations (5–10g/ml) surface filaments disappeared and the cells flattened and spread against the glass surface. Cytoplasmic fusion bridges were observed in areas where cells made contact. Concentrations of Con A ranging between 50–500 g/ml caused cell shrinkage and surface distortions without cell flattening and filament loss. These morphologic effects were not apparent if Con A binding sites were blocked by preincubation with -methyl-D-mannopyranoside before application to the cell cultures. However, once the Con A-mediated changes were in effect, the cells failed to show recovery when they were returned to growth medium and a majority of the cells on the coverglasses degenerated. Presumably the cells whose morphology appears unaffected by Con A treatment are the survivors that repopulate cultures returned to growth medium.Supported by Grants CA-12600 and CA 16619 awarded by the National Cancer Institute, DREW and in part by NIH Biomedical Sciences Grant No. RR-07050. CAA's participation in this project was supported by Training Grant No. 5T01-GM-71-17We wish to thank Dr. Imogene Schneider for providing the cell lines     

The effects of lectins on the interaction between macrophages and bone in vitro

Summary Recent studies have demonstrated that the attachment of elicited rat macrophages to bone is mediated by specific saccharides located on the cell and/or bone surfaces. We have used a macrophage-bone culture system to study the effects of two lectins, concanavalin A (con A) and soybean agglutinin (SBA), on the morphology of macrophage attachment to a devitalized bone surface and subsequent functional activity. Macrophages were obtained from 3- to 4-week-old rats by peritoneal lavage and the adherent pool was used to prepare cell suspensions. Con A-treated, SBA-treated or control cell suspensions were aliquoted onto the endocranial surface of devitalized rat calvariae. The cells were allowed to attach for 1 h at 37° C, after which, the bone samples were removed from culture and prepared for scanning electron microscopy (SEM). The morphology of con A-treated macrophages attached to bone was markedly different from that of control or SBA-treated cells. Con A altered the attachment and subsequent spreading of macrophages on bone as visualized by SEM. Furthermore, the number of con A-treated cells that attached to bone and the average surface area of cell membrane apposed to the matrix was significantly different from that of control or SBA-treated cells. A ⁴⁵Ca bone-release assay was performed to evaluate the functional significance of the morphological findings. Lectin-treated or control cell suspensions were allowed to attach to the endocranial surface of ⁴⁵Ca pre-labeled calvariae for 1 h. Following attachment, the samples were cultured for 72 h. The con A-treated cultures demonstrated a significant decrease in the release of ⁴⁵Ca after 48 and 72 h in comparison to control cultures, while the ⁴⁵Ca released from SBA-treated cultures did not differ significantly from controls. These results suggest that certain sugar residues common to membrane-associated glycoconjugates and the organic component of the bone matrix regulate the attachment of macrophages to bone and their subsequent bone-resorbing activity.     

Concanavalin A/IFN-gamma triggers autophagy-related necrotic hepatocyte death through IRGM1-mediated lysosomal membrane disruption

Interferon-gamma (IFN-γ), a potent Th1 cytokine with multiple biological functions, can induce autophagy to enhance the clearance of the invading microorganism or cause cell death. We have reported that Concanavalin A (Con A) can cause autophagic cell death in hepatocytes and induce both T cell-dependent and -independent acute hepatitis in immunocompetent and immunodeficient mice, respectively. Although IFN-γ is known to enhance liver injury in Con A-induced hepatitis, its role in autophagy-related hepatocyte death is not clear. In this study we report that IFN-γ can enhance Con A-induced autophagic flux and cell death in hepatoma cell lines. A necrotic cell death with increased lysosomal membrane permeabilization (LMP) is observed in Con A-treated hepatoma cells in the presence of IFN-γ. Cathepsin B and L were released from lysosomes to cause cell death. Furthermore, IFN-γ induces immunity related GTPase family M member 1(IRGM1) translocation to lysosomes and prolongs its activity in Con A-treated hepatoma cells. Knockdown of IRGM1 inhibits the IFN-γ/Con A-induced LMP change and cell death. Furthermore, IFN-γ(-/-) mice are resistant to Con A-induced autophagy-associated necrotic hepatocyte death. We conclude that IFN-γ enhances Con A-induced autophagic flux and causes an IRGM1-dependent lysosome-mediated necrotic cell death in hepatocytes.     

Alterations in the surface glycoproteins of chicken erythrocytes following transformation with erythroblastosis strain R virus

Summary Erythroblasts from marrows of chicks infected with RNA-virus (strain Rerythroblastosis virus) were found to possess a small but consistent increase in the number of concanavalin A binding sites per cell compared to erythroblasts derived from the marrows of phenylhydrazine-treated birds. Both types of erythroblast possessed more surface glycoproteins per cell accessible to concanavalin A (Con A) than marrow and peripheral blood erythrocytes. Employment of concanavalin A conjugated to ferritin showed marked differences in the spatial arrangement of the Con A receptors between phenylhydrazine and virus-induced erythroblasts but little difference was observed in the surface density of the Con A sites between erythrocytes and erythroblasts, a result which agrees with the amount of bound labeled Con A when this data is expressed in terms of the cell surface.The amount of labeled Con A bound to erythrocytes derived from the marrow was greater than that derived from the peripheral circulation, a result which is substantiated by the ferritin Con A studies which show an increase in the density of Con A sites on the marrow blood cells. Trypsinization increases the number of sites and the agglutininability of the marrow cells.The increase in the susceptibility of the cells to agglutinate with concanavalin A paralleled the observed increase in the number of binding sites per cell.