Augmentation of galactose-specific glycoproteins during corneal epithelial migration in organ culture

The purpose of the present study was to identify galactose-specific glycoproteins that are synthesized in higher amounts or downregulated during the migratory process of corneal epithelium. Trichloroacetic-acid-precipitable proteins showed an increased incorporation of (3)H-galactose with time in migrating corneal epithelium in organ culture. Galactose oxidase treatment of immobilized 3-[(3-cholamidopropyl)dimethylamminio]-1-propanesulfonate-extractable glycoproteins of migrating and nonmigrating corneal epithelia resolved on sodium dodecylsulfate polyacrylamide gel electrophoresis was carried out. Two prominent terminally galactosylated protein bands (180 and 98 kD) were seen in the migrating epithelium but were absent in the nonmigrating epithelium. We conclude that during the migratory process of the corneal epithelium there is an increased utilization of galactose, and galactose-specific glycoproteins are synthesized in higher amounts.

Fluorometric determination of mucin-type glycoproteins by the galactose oxidase-peroxidase method

We developed a convenient and specific method for the determination of mucin-type glycoproteins using galactose oxidase and horseradish peroxidase on the basis of the contents of galactosyl and N-acetylgalactosaminyl residues in glycoproteins. Galactose and galactosamine residues released from glycoproteins after hydrolysis were oxidized with galactose oxidase and subsequently the resultant hydrogen peroxide was determined by a combination of horseradish peroxidase and 3-(p-hydroxyphenyl) propionic acid as a fluorogenic substrate. The contents of galactose/galactosamine residues in N- and O-glycans, as determined by the galactose oxidase-peroxidase method, were in good agreement with those described in the previous reports. We applied the present method to determine mucin-type glycoproteins secreted from rat gastric mucosa by stimulation with misoprostol, a prostaglandin E(1) analogue in vivo. Thus, the galactose oxidase-peroxidase method is useful for the determination of mucin-type glycoproteins in biological materials.

Galactose oxidase-glucan binding domain fusion proteins as targeting inhibitors of dental plaque bacteria

In order to inhibit the growth of bacteria present in the human oral cavity, a novel system which targets antimicrobial agents to dental plaque has been developed. This system involves a hybrid protein consisting of a peptide expressing the bactericidal properties of galactose oxidase (GAO) fused to the glucan binding domain (GBD) of the Streptococcus mutans glucosyltransferase-S enzyme. A gene encoding GAO from the fungus Fusarium sp. has been inserted into an Escherichia coli expression vector and fused to sequences encoding the GBD, which binds to the glucans synthesized by oral streptococci. Bacterial extracts expressing the hybrid protein were tested for their ability to target the GAO activity to an in vitro plaque model consisting of streptococcal cells bound to microtiter plate wells. The binding of the hybrid protein to the streptococcal cells through its GBD and the dependence of binding on the production of glucans by bacteria were demonstrated. Furthermore, killing of three different species of oral streptococci by bound hybrid protein in conjunction with the galactose-lactoperoxidase-iodide cytotoxic system has been demonstrated. These results suggest a novel strategy for controlling dental plaque formation as well as dental caries in humans.

Establishment of monoclonal antibodies against carbohydrate moiety of gastric mucins distributed in the different sites and layers of rat gastric mucosa

Eight monoclonal antibodies (MAbs), designated RGM21 approximately RGM42, were generated against mucin purified from the rat gastric mucosa. By applying ELISA, all of these MAbs were proved to react not only with the purified mucin, but also with the oligosaccharide mixture obtained from the antigenic mucin by alkaline borohydride treatment. Treatment of the mucin-attached ELISA well with trypsin, sodium periodate or galactose oxidase prior to the addition of the MAb was applied to characterize these MAbs. Histochemical observation indicated that all these MAbs were able to stain the formalin fixed-paraffin embedded sections of the rat gastroduodenal mucosa. Although each of these MAbs reacted with distinct mucus-producing cells localized in particular regions of the gastroduodenal mucosa, their staining specificity could generally be classified into four groups. These MAbs might be useful for estimating the physiological and pathological changes of mucins in the gastric mucosa.

Modification of the sialic acid residues of choriogonadotropin affects signal transduction

Human choriogonadotropin (hCG) is a glycoprotein hormone that activates adenylyl cyclase. The carbohydrate moieties of hCG are required for biological activity, but not for binding to the gonadotropin receptors. We modified N-acetylneuraminic acid (NeuAc) on the oligosaccharide moieties of hCG, and determined the effect on its biological activity by measuring hormone-stimulated adenylyl cyclase. Treating hCG with sodium periodate to remove two carbon atoms from NeuAc or quantitatively removing NeuAc from hCG reduced its biological activity by 36% and 50%, respectively. The galactose residues of asialo-hCG were reacted with NeuAc-hydrazone or a hydrazone of the oligosaccharide from the ganglioside GM1 (Gal(beta 1-3)GalNAc(beta 1-4) [NeuAc(alpha 2-3)]Gal(beta 1-4)Glc). The gonadotropin receptor had high affinity for both derivatives, but their biological activity was less than that of hCG. These results suggest that several structural aspects of NeuAc including carbon side chain, an intact ring structure, and the position of NeuAc relative to other carbohydrate residues are important for full biological activity of hCG.

A diagnostic assay for the Wiskott-Aldrich syndrome and its variant forms

BACKGROUND

The Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disease characterized by severe thrombocytopenia, eczema, and impaired immunity. While the diagnosis is usually straightforward, the syndrome may be expressed in an attenuated form, a phenotype which is difficult to distinguish from other types of congenital thrombocytopenia. Although a molecular-based assay for diagnosis of the spectrum of WAS patients has not been available, recent data indicate that WAS is associated with a specific profile of impaired mitogen responsiveness and suggest that detection of this abnormality may provide a diagnostic marker for all forms of the disease. To address this issue, we have studied patients with classical and atypical WAS for their lymphocyte proliferative responses to four T cell mitogenic stimuli and compared their response patterns to those detected in unaffected children.

METHODS

Clinical histories and informed consent were obtained from 23 patients with either classical or putative (ie, atypical) WAS, 16 subjects with other disorders, and 12 healthy children. Peripheral blood mononuclear cells (PBMCs) collected from patients and controls were resuspended in culture medium, stimulated with the T cell mitogens phytohemagglutinin (PHA), concanavalin A (Con A), neuraminidase/galactose oxidase (NAGO), or periodate, and cultured for 60 h in 0.2 mL aliquots. Following a 20 h pulse with 3H-thymidine, cultures were harvested and the 3H-thymidine uptake was evaluated by liquid scintillation counting.

RESULTS

The most striking observation involved response to periodate. While lymphocytes from all healthy control children proliferated in response to periodate treatment, cells from both classical as well as atypical WAS patients consistently failed to proliferate in response to this mitogen. By contrast, lymphocyte proliferative responses to PHA, Con A, and NAGO were detected in all patients and controls, although responses generally were lower in cells from classical WAS patients compared to other children. In two WAS patients, bone marrow transplantation and clinical improvement were associated with a change from no periodate response (pre-transplant) to periodate responsiveness (post-transplant). In contrast to the WAS patients, cells from patients with other hematologic and primary immune deficiency diseases responded uniformly to all four mitogens, including periodate.

CONCLUSIONS

The data presented here indicate that T cells from patients with either classical or attenuated WAS fail to undergo proliferation in response to periodate, an agent that induced extensive T cell mitogenesis of cells from all healthy controls as well as patients with diseases other than WAS. As the WAS patients' cells did proliferate in response to treatment with other T cell mitogens, it appears that periodate induced T cell proliferation is selectively impaired in WAS and that detection of this defect may be of value in the distinction of both classical and attenuated WAS from other thrombocytopenic conditions.

The cytosolic activating factors p47phox and p67phox have distinct roles in the regulation of electron flow in NADPH oxidase

We have previously shown that the human neutrophil superoxide-generating NADPH oxidase possesses a novel dye reductase activity (Cross, A.R., Yarchover, J. L., and Curnutte, J.T. (1994) J. Biol. Chem. 269, 21448-21454). This activity exhibited an absolute requirement for the cytosolic activating factor p67phox but not for p47phox, suggesting that p67phox and p47phox have individual roles in controlling electron flow from NADPH to oxygen. Here, we provide direct evidence that p67phox alone can facilitate electron flow from NADPH to the flavin center of NADPH oxidase in the absence of p47phox, resulting in the reduction of enzyme FAD, whereas the presence of p47phox is required in order for electron transfer to proceed beyond the flavin center to the heme in cytochrome b-245 and thence to oxygen.

Galactosylated histone-mediated gene transfer and expression

We have developed a novel, highly efficient DNA delivery system to accomplish gene transfer through the asialoglycoprotein receptor-mediated endocytosis pathway. Natural nuclear DNA-binding proteins, the histones (H1, H2a, H2b, H3, and H4), were modified and used as receptor-targeted DNA carriers. Galactosylated with a coupling agent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, the histones and albumin were conjugated to DNA and then used to transfect HepG2 cells, which display the asialoglycoprotein receptor. The extent of galactosylation was determined for all histone subgroups and albumin with 14C-labeled galactose. A reporter gene for the bacterial chloramphenicol acetyltransferase (CAT), under the control of the 5' long terminal repeat (LTR) of Rous sarcoma virus, was used for comparisons of transfection efficiency of various carrier proteins. The CAT activity resulting from histone H1-mediated transfection was 1.66 unit per 10(6) cells, the highest among histone subgroups. The galactyosylated histone H1 was also eleven times more effective than the asialo-orosomucoid-polylysine. Ten galactosyl units are attached to histone H1 by the galactosylation reaction. Differences in the extent of galactosylation could not explain different transfection efficiencies among various proteins studied in this report. Treatment with galactose oxidase abolished the transfection ability of both the galactosylated histone H1 and asialo-orosomucoid. The intrinsic DNA-binding domains and nuclear location signal sequences are unique to histones as receptor-targeted DNA carriers, and are advantageous for effective gene delivery.

Transient hyperglycosylation of rhodopsin with galactose

Rhodopsin's oligosaccharide chains contain predominantly two types of sugar residues: mannose and N-acetylglucosamine. In the present work, bovine and rat rhodopsin were analysed biochemically for the presence of a third sugar, galactose. Treatment of bovine rod outer segments (ROS) with galactose oxidase followed by reduction with tritium-labeled sodium borohydride revealed the presence of existing molecules of galactose on rhodopsin. Rats injected intravitreally with [3H]galactose and [14C]leucine and maintained in darkness were killed 1 hr, 6 hr, 1, 3 or 5 days following the injection. Retinas were collected for subcellular fractionation and rhodopsin from each of the fractions was purified by ConA sepharose chromatography and SDS-PAGE. During the first 6 hr, galactose selectively labeled rhodopsin in the Golgi-enriched fraction resulting in increased [3H]/[14C] ratios in both Golgi and ROS. The data suggested that trimming was occurring at the transition from Golgi to ROS. Furthermore, a decrease in isotope ratio in the ROS between 6 hr and 1 day suggested further trimming of rhodopsin after membrane assembly in the ROS. Additional in vivo experiments demonstrated existing molecules of galactose on rhodopsin's oligosaccharide chain using lectin affinity chromatography. Rats injected intravitreally with [35S]methionine were dark-adapted for 2 hr. Following subcellular fractionation of retinas, ConA purified rhodopsin from ROS was applied to one of two additional lectin columns: Ricinus communis agglutinin (RCA) or Griffonia simplicifolia I (GSA). Eight to nine percent of the labeled rhodopsin was bound to and eluted from RCA, whereas none bound to GSA, indicating the presence of a beta-galactoside. The RCA agarose eluted protein co-electrophoresed with a rhodopsin standard and was light sensitive. Galactose was shown to be the terminal sugar on this subset of rhodopsin and was not capped by neuraminic acid. Binding of rhodopsin's oligosaccharide to RCA was abolished by pre-treatment with beta-galactosidase. Decreased binding of rhodopsin to RCA was observed following intravitreal injection of castanospermine but not swainsonine. Of those two inhibitors of glycoprotein trimming, only castanospermine would be expected to prevent the addition of galactose to the oligosaccharide. The association of galactose with rat rhodopsin appeared to be a transient one. At 2 hr, 8-9% of rhodopsin contained galactose, at 6 hr only 2.2% had galactose and by 24 hr less than 1% did. The galactose was trimmed from rhodopsin's oligosaccharide presumably after its role was complete. Separation of rhodopsin of the plasma membranes from rhodopsin of discs indicated that 75% of the galactose-containing rhodopsin was in the plasma membrane and only 25% was in the discs. These findings suggested a possible role for galactose in new disc formation with subsequent removal after the discs are sealed.

The accessory function of B lymphocytes is resistant to the adverse effects of UV radiation

The effect of UV radiation on the accessory activities of B lymphoblastoid cell lines (B-LCL) was investigated in three types of in vitro T lymphocyte proliferation assay, each of which differed in its accessory requirements. In contrast to monocytes whose accessory function was universally sensitive to UV radiation, B-LCL were resistant to UV in oxidative mitogenesis and staphylococcal enterotoxin B assays, in which stimulus processing was not a requirement. Expression of membrane interleukin (IL) 1 and HLA-DR antigens by B-LCL and monocytes was not affected by UV, nor was surface membrane expression of intercellular adhesion molecule-1 (ICAM-1) on B-LCL. These results were in marked contrast to monocytes in which there was a greater than 65% reduction in ICAM-1 expression. When UV-irradiated B-LCL were employed as antigen-presenting cells for tetanus toxoid-dependent T cell stimulation, a reduction in antigen-presenting function was observed. However, pulsing of B-LCL with tetanus toxoid prior to UV irradiation preserved their antigen-presenting capacity in this system also. These findings indicate that there is differential UV sensitivity among accessory cells which may be explained by different effects of UV radiation on antigen processing and adhesion molecule expression.

Accessory cells induce a polyphosphatidylinositol response when cultured with mitogen-activated T lymphocytes

Monocytes (MO) influenced phosphoinositide metabolism when human T lymphocytes, isolated from peripheral blood, were activated by polyclonal mitogens. In the 3 hr immediately following mitogenic challenge, the synthesis of phosphatidylinositol (PI) was augmented and the synthesis of PI-4-phosphate (PIP) and PI-4,5-bisphosphate (PIP2) was induced in cultures of T lymphocytes and MO. In addition, MO induced a rapid and transient degradation of PIP and PIP2 in T cells prelabeled with [32P]PL and subsequently activated by mitogen. Induction of a PIP/PIP2 response correlated well with induction of DNA replication by MO when T cells were activated by phytohemagglutinin or by neuraminidase plus galactose oxidase. MO did not influence polyphosphoinositide metabolism when T cells were stimulated by the nonmitogenic lectin wheat germ agglutinin. Interleukin 1 could not substitute for monocytes in inducing a polyphosphoinositide response. By causing a rapid and transient release of the second messengers diacylglycerol and inositol phosphates and by subsequently increasing their cellular precursors, MO may induce the interleukin 2 responsive state in T lymphocytes.

Modification of triantennary glycopeptide into probes for the asialoglycoprotein receptor of hepatocytes

Triantennary glycopeptide was oxidized with galactose oxidase to convert the -CH2OH group on terminal galactose residues to the aldehyde group (oxo-form). Kinetic profiling by reverse phase high performance liquid chromatography allowed termination of the reaction when intermediate mono-oxo- and di-oxo-triantennary glycopeptides had been produced. The mixture of the oxo-glycopeptides was derivatized with 2,4-dinitrophenylhydrazine for efficient separation, and each isomeric triantennary hydrazone was separated by reverse phase high performance liquid chromatography. The purified hydrazones were reverted to three original isomeric mono-oxo- and di-oxo-glycopeptides, and a single tri-oxo-glycopeptide. Each of these isomers was characterized by proton NMR by a downfield shift in the anomeric signals of 6-oxo-Gal residue(s). The functionalized glycopeptides were successively modified with dansyl and naphthyl groups through the 6-oxo-Gal residue and the amino terminus of the peptide to prepare three isomeric glycopeptide probes suitable for conformation studies by fluorescence energy transfer measurements. Alternatively, glycopeptides were derivatized by attaching t-butyloxycarbonyl-L-tyrosine to the amino terminus of the peptide, and reductive amination of the 6-oxo-Gal residue, provided three isomeric triantennary photoaffinity probes which allow photolyzable groups to be attached to the newly introduced 6-amino-Gal residue.

[The mitogenic properties of Fusarium graminearum and Rhodococcus erythropolis enzymes]

Blast transformation of peripheral blood lymphocytes in healthy people is studied by enzymes of the microbic origin possessing the lectin activity. Galactose oxidase of Fusarium graminearum IMV-F-1060 is shown to be mitogenically active with respect to the lymphocytes in the culture in vitro and may be one of home sources of lymphocytic mitogens for the laboratory investigations.

Mechanism of production of interferon-gamma: role of arachidonic acid metabolites

The effects of arachidonic acid metabolites on mitogen-induced interferon (IFN)-gamma production by human peripheral blood mononuclear cells (PBMC) were examined. Both prostaglandins E2 (PGE2) and leukotrienes B4 (LTB4) were produced after macrophage activation stimulated by galactose oxidase (GO) and Staphylococcal enterotoxin B (SEB), two well known inducers of IFN-gamma. To test the involvement of PGE2 and LTB4 in IFN-gamma production, GO- and SEB-activated PBMC were treated with two inhibitors of cyclooxygenase (aspirin and indomethacin) and with an inhibitor of lipoxygenase [nordihydroguaiaretic acid (NDGA)]. The results of these experiments showed that aspirin and indomethacin cause a marked increase of IFN-gamma production by GO- and SEB-activated PBMC. On the contrary, NDGA treatment reduced IFN-gamma production induced by the same agents. Moreover, whereas the addition of exogenous PGE2 reduces IFN gamma production, the addition of exogenous LTB4 does not affect IFN-gamma production. Taken together these findings indicate that arachidonic acid metabolites, produced during mitogenic activation, are involved in the regulation of IFN-gamma production and suggest that, in our system, LTB4 exerts a positive modulating signal while PGE2 represents a negative signal.

Mechanism of human interferon-gamma production: involvement of beta-2-microglobulin

The ability of several monoclonal antibodies (MoAbs) against beta-2-microglobulin (beta 2m) to inhibit interferon-gamma (IFN) production was assayed in peripheral blood mononuclear cells (PBMC). All of them strongly reduce IFN-gamma induction by galactose oxidase (GO), a well-characterized enzyme capable of activating T lymphocytes through mediation of macrophages. In contrast, many MoAbs directed against HLA class I (heavy chain) and class II antigens do not inhibit IFN induction by GO. On the other hand, anti-beta 2m MoAbs do not effectively reduce IFN-gamma induction by A23187, a calcium ionophore that acts on T cells in the absence of accessory cells. Competition experiments demonstrate that (i) the inhibition of anti-beta 2m antibodies was specific for beta 2m protein, and (ii) beta 2m is not itself the site of action of GO. Moreover, it is demonstrated that the addition of beta 2m to oxidated PBMC strongly enhances subsequent IFN-gamma production. Oxidation of galactose residues on glycoproteins of macrophage membrane is an obligate step for IFN-gamma induction whatever the inducer, thus our results suggest that beta 2m is involved in the mechanism of induction of IFN-gamma.

Non-specific propagation of human antigen-dependent T lymphocyte clones

Most T lymphocyte clones require periodical restimulation with specific antigen in addition to growth factors to maintain long-term growth in vitro. Since in many cases the specific antigen for a given T cell clone is not known or not available, alternative methods of stimulation are required. In this report a method for a non-antigen-specific stimulation of antigen-dependent proliferative or cytotoxic human T cell clones is described. Introduction of aldehydes into galactose residues on stimulator cells leads to the stimulation of T cell clones by modified stimulator cells in the absence of a mitogen. This system is as efficient as the use of mitogenic antibodies or lectins but avoids the disadvantages of these polyclonal T cell activators.

Determination of mitogenic properties and lymphocyte target sites of Dolichos lablab lectin (DLA): comparative study with concanavalin A and galactose oxidase cell surface receptors

A mannoside-directed lectin has been isolated and purified from the seeds of Dolichos lablab L. by affinity chromatography. We have established that this glycoprotein, which displays high erythroagglutinating activity without blood group specificity, highly activates murine T lymphocytes, and we have described for the first time its mitogenic properties. Although its main properties are close to those of concanavalin A (Con A), the well-known mannoside-directed mitogen devoid of sugar moiety, several differences were found in some of the early events triggered by the two lectins during lymphocyte mitogenic stimulation: higher level of interleukin-2 (IL-2) synthesis, optimal dose for IL-2 synthesis at suboptimal mitogenic concentration, lack of ecto-5' nucleotidase inhibition, and lack of mitogenic inhibition at high lectin concentration. Because the two lectins did not act on the cell surface in exactly the same way, we have compared their receptors involved in mitogenesis on the plasma membrane of murine lymphocytes. We had previously established that the polyclonal activation of these cells probably occurred through high-molecular-weight receptors (200-230 kDa). Since the mitogenic stimulation of lymphocyte by galactose oxidase (GO), like that of Con A, was inhibited by DLA, we analyzed the cell surface receptors that were common to these three polyclonal mitogens. After labeling the neuraminidase/GO-treated cell surface glycoproteins with NaB3H4, we immunoprecipitated the Con A and DLA receptors which are the target of GO mitogenic action. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the precipitates demonstrated that there exist on the lymphocyte cell surface receptors common to the polyclonal mitogens DLA, Con A, and GO. Because Con A and DLA sterically inhibit GO mitogenic stimulation, the common glycoproteins which represent the necessary sites of oxidative mitogenic action are probably those which are involved in DLA and Con A-triggered mitogenesis, despite the different properties of the two lectins. These differences could be explained by the lower molecular weight receptors of the two lectins which are not identical.

Accessory cell-independent activation of T cells by oxidized red blood cells plus polyethylene glycol

We have previously shown that the combination of neuraminidase-galactose oxidase (NAGO)-treated autologous erythrocytes (EOX) and polyethylene glycol (PEG) is highly mitogenic for human peripheral blood lymphocytes (PBL). In this report, we show that EOX plus PEG-induced T lymphocyte proliferation is independent of HLA-DR and Leu M3-positive accessory cells (AC). Purified T (pT) cells and PBL were equally stimulated by EOX + PEG, while pT cells were unresponsive to the mitogens phytohemagglutinin (PHA), NAGO, and the anti-CD3 antibody UCHT1, even in the presence of PEG. These findings indicate that specific signals from AC may be replaced by unspecific stimuli in T cell activation.

Selective, histamine-mediated immunosuppression in laryngeal cancer

Immunosuppression observed even in the earliest laryngeal cancers can be, in part, reversed with H2 histamine antagonists. In an effort to explain this, we tested whether histamine could evoke changes in endogenous antitumor lymphokine production using tonsil lymphocytes as test cells. We have observed that lymphocytes, treated in vitro with histamine, display a significant suppression of lymphokine production and mixed lymphocyte proliferation response following galactose oxidase treatment. Interferon gamma production was reduced to less than 2% of control value in the presence of histamine. In contrast, the lymphokine-activated killer cell activity induced by purified, natural interleukin-2 was not affected by similar concentrations of histamine. Histamine appears to exert its inhibitory effect by stimulating the production of a substance released by suppressor T cells. The suppressive effects observed could be reversed by concomitant or sequential treatment with cimetidine or ranitidine and not by H1 histamine antagonists, indicating that it occurs through an H2 histamine receptor. These experiments suggest that histamine may have a profound suppressive effect on the lymphocyte population studied.

The regulation by low-density lipoproteins of the activation of oxidative enzyme-primed lymphocytes is governed by transferrin

The activation of T lymphocytes was regulated in vitro by low-density lipoproteins (LDL). Not all prereplicative events induced by the oxidative enzymatic mitogens neuraminidase and galactose oxidase (NAGO) were susceptible to inhibition by LDL. The accessory cell-independent early blastogenic response was not suppressed. LDL suppressed accessory cell-dependent responses, and the extent of LDL suppression, depended on the concentration of transferrin. A gradient of transferrin determined the point in the cell cycle at which NAGO-primed lymphocytes were suppressed by LDL. When transferrin was low (0-10 micrograms/ml) and in serum-free medium (SFM), LDL suppressed the expression of cell surface receptors for interleukin-2 (IL-2R) and transferrin (TfR), the late blastogenic response prior to DNA replication (72 hr), and DNA replication. At higher levels of transferrin, about 100 micrograms/ml, the LDL-suppressed cells were IL-2R+, TfR+ and responsive to IL-2, but did not enter S phase. LDL suppression could be ablated by IL-2 and by high levels of transferrin (250-1000 micrograms/ml). In RPMI medium containing serum (FBS), the pattern of LDL suppression was different from that in SFM: fully activated IL-2R+, TfR+ lymphocytes were unresponsive to exogenous IL-2, suggesting that they were blocked at the G1/S boundary. This block was also relieved by transferrin (greater than 100 micrograms/ml). The data suggest that the interplay between transferrin and LDL is a critical factor in the NAGO-induced stimulation of T lymphocytes. LDL and transferrin exert negative and positive control of lymphocyte activation, respectively. In SFM, LDL appear to alter transferrin utilization by accessory cells; in RPMI-FBS, by fully activated T lymphocytes.

The selective activation of T8+ cells by neuraminidase and galactose oxidase is mediated by activated T4+ cells

The response of highly enriched populations of human T8+ lymphocytes to the oxidative mitogenic enzymes neuraminidase (NA) and galactose oxidase (GO) was enhanced by NAGO-primed T4+ lymphocytes. No similar enhancement occurred when the cells were primed with phytohemagglutinin (PHA). In the absence of subclass contamination (1%), the T8+ and T4+ cells responded equally to NAGO by the criterion of DNA replication. The addition of a small number, 2-10%, of NAGO-T4+ cells to the NAGO-T8+ cells enhanced DNA synthesis by as much as 8.5-fold. Augmentation of the cellular response did not occur unless the T4+ cells were activated by NAGO. The converse situation, 2-10% of NAGO-T8+ cells in a primarily NAGO-T4+ cell population, did not increase the DNA synthetic response of the NAGO-T4+ cells. The NAGO-T4+ cells did not augment the early event of increased phosphatidylinositol metabolism or the midcycle event of induction of receptors for interleukin 2 (IL2) and transferrin. The NAGO-T4+ cells therefore increased the probability that fully activated T8+ lymphocytes crossed the G1/S boundary. The basis for this effect was not an enhanced responsiveness of the NAGO-T8+ cells to IL2 or to other soluble growth mediators in medium conditioned by NAGO-activated lymphocytes. The results of this investigation thus implicate a control point in the NAGO-T8+ lymphocyte cell cycle that is positively modulated by the NAGO-T4+ cells themselves or by a product of their activation.

Enzymatic characterization of peanut agglutinin-binding components in the retinal interphotoreceptor matrix

Previous histochemical and biochemical studies have documented the presence of carbohydrate-containing molecules in the retinal interphotoreceptor matrix (IPM). The lectin peanut agglutinin (PNA), which preferentially binds galactose-containing carbohydrates, especially galactose-galactosamine linkages, selectively labels cone photoreceptor-associated domains of the IPM ('cone matrix sheaths') in a variety of vertebrate retinas. In the studies described here, the nature of these PNA-binding components was investigated by monitoring the effects of proteolytic and glycosidic enzymes on binding of the lectin in the retina and IPM. All proteolytic enzymes tested cause a marked reduction in PNA-binding to cone matrix sheaths, suggesting that proteinaceous components are important to their organization. Exposure to O-glycanase, but not N-glycanase, markedly reduces binding of PNA to cone matrix sheaths indicating that O-linked oligosaccharides are probably responsible for its binding. Galactose oxidase treatment reduces PNA-binding throughout the retina and IPM, confirming that galactose moieties are involved in its binding. beta-Galactosidase (either before or after neuraminidase treatment) does not alter the pattern of PNA binding, suggesting that neither terminal nor penultimate beta-linked galactose residues constitute a major proportion of the lectin's binding sites in the retina. Neuraminidase treatment markedly increases the density and distribution of PNA binding throughout the retina and IPM, however, this effect appears to be, at least in part, the result of the binding of the lectin to neuraminidase molecules that become associated with tissue sections in addition to binding to carbohydrate groups unmasked by desialation. Exposure to chondroitinases causes disruption of the morphological integrity of cone matrix sheaths and slight diminution of PNA binding. Other enzymes acting on common constituents of extracellular matrices do not have similar effects. Taken together, these observations suggest that PNA-binding to cone matrix sheaths is due to the presence of glycoconjugates with galactose-containing, O-linked oligosaccharide chains.

Stimulation of human lymphocytes by oxidized red blood cells (RBC) in the presence of polyethylene glycol (PEG)

In the present work, it is shown that oxidized red blood cells (RBC) in the presence of polyethylene glycol (PEG) is a powerful cellular class-II MHC-free mitogen for human lymphocytes. Human lymphocytes were stimulated with oxidized autologous human RBC or sheep RBC in the absence or presence of PEG, M.W. 10,000. The RBC were oxidized with the enzyme combination neuraminidase-galactose oxidase or with sodium periodate. The presence of PEG strongly potentiated the response. Optimal stimulatory conditions were obtained with a 10:1 ratio of oxidized RBC to lymphocytes and a PEG concentration of 25 +/- 5%.

Plasmodium berghei: reaction of sporozoites with chemically and enzymatically modified hepatoma cells

Plasmodium berghei sporozoites were observed to react with human hepatoma (HepG2) target cells which had been fixed with methanol, formaldehyde, or glutaraldehyde. The reaction consisted of attachment of sporozoites to the fixed target cells and the release of circumsporozoite protein which bound to target cell areas adjacent to the attachment sites. Treatment of fixed target cells with 0.1 N H2SO4 at 80 C, neuraminidases, neuraminidase plus galactose oxidase or inclusion of transferrin, orosomucoid, their asialo forms, or various monosaccharides in the incubation medium had no significant effect on target cell reactivity with sporozoites. Fixed cells oxidized with periodate or cells extracted with methanol or chloroform-methanol were reactive but lost activity if allowed to air dry after treatment. Treatment with papain or chymotrypsin at levels producing heavy cell structure damage caused a major loss of activity.

Multiple pathways for antigen-independent activation of a T helper hybridoma

An important question in mitogen activation of T cells is whether the T cell must interact with a major histocompatibility complex product during the activation process. The T helper hybridoma AODH 7.1 is specific for human gamma globulin in the context of IEd, and when activated secretes interleukin 2. The mitogen concanavalin A (Con A) can activate AODH 7.1 cells directly, but two other standard T cell mitogens, phytohemagglutinin (PHA) and neuraminidase-galactose oxidase, cannot. However, Con A, PHA and neuraminidase-galactose oxidase could all activate AODH 7.1 when presented on various cloned class II+ cell lines. There was an absolute requirement for the presentor cell to be class II+, and the activation signal on mitogen-treated class II+ presentor could be blocked by monoclonal antibody to the class II antigens. To determine if class II molecules were absolutely required for the presentation of a mitogen activation signal we used class II- LtK- L cells and two LtK- cell class II gene transformants as presentor cells. Only the class II+ transformants, but not the class II- LtK- cells, could present either Con A or PHA. The class II requirement cannot be bypassed through provision of soluble factors. However, when Con A was used to activate AODH 7.1 cells directly, it appeared to be acting in a transmembrane fashion. It was not the case that AODH 7.1 cells were responding to Con A on a neighboring AODH 7.1 cell, and no class II antigens were involved. These results are consistent with the idea that different routes of activation exist for T cells, at least at the level of signal recognition.

In vitro attachment of mono- and oligosaccharides to surface glycoconjugates of intact cells

We have synthesized glycosylhydrazines of various mono- and oligosaccharides and coupled these to periodate- or galactose oxidase-treated human red cells and K562 erythroleukemia cells. The optimal conditions for this carbohydrate modification of cells have been established. This method makes it possible to specifically elongate oligosaccharide chains of cell surface glycoconjugates with desired carbohydrates. In this way, new antigenic and receptor properties can be conferred to cells, and the functional roles of carbohydrates in cell surface glycoconjugates can be studied. The method has been used to make red cells of blood group O reactive with anti-A and anti-B sera, and in rendering K562 cells or red cells of blood group O agglutinable with the alpha-N-acetylgalactosamine-specific Helix pomatia lectin.

The extent of oxidative mitogenesis does not correlate with the degree of aldehyde formation of the T lymphocyte membrane

Chemical oxidation of T lymphocytes with periodate or the combined action of the enzymes neuraminidase and galactose oxidase (NAGO) results in T cell activation. The latter process includes the production of interleukin 2 (IL 2) and the induction of IL 2 receptors. Because membrane-bound aldehydes act in the transmission of the oxidative mitogenic signal, we designed a comparative study in human thymocytes and peripheral blood leukocytes in order to determine a possible correlation between the degree of the membrane aldehydes generated chemically or enzymatically and the extent of the resulting activation. The differences between periodate- and NAGO-induced aldehydes were demonstrated by flow cytometry of cells stained with a novel fluoresceinated hydrazide and by an electrophoretic procedure performed with biocytin hydrazide and 125I-streptavidin. In both cellular systems, periodate oxidation resulted in stronger formation of aldehydes than NAGO oxidation. However, the IL 2 receptor induced by NAGO formation and the resultant activation were significantly higher than those induced by periodate. The degree of aldehyde formation on peripheral blood leukocytes was also considerably higher than that of thymocytes, yet similar patterns of [3H]thymidine uptake were observed in the mitogenic assays of both cellular systems. The data indicate that no correlation exists between the extent of aldehyde formation and the degree of oxidative mitogenesis. It is thus suggested that relatively few (or maybe only one) membrane-bound aldehyde-containing molecules act in the transmission of the oxidative mitogenic signal.

Exposure of major neutral glycolipids in red cells to galactose oxidase. Effect of neuraminidase

The exposure of several major red-cell glycolipids to galactose oxidase was studied by oxidizing the cells with the enzyme and reducing them with NaB2H4. After isolation, the deuterium label was detected by mass fragmentography. 60-70% globoside in human and porcine erythrocytes was exposed as measured by this method. In contrast, asialo-GM2 in guinea-pig erythrocytes and Forssman glycolipid in sheep erythrocytes were mainly in a cryptic state. Neuraminidase treatment increased the incorporation of deuterium label to asialo-GM2 4-8-fold. A similar effect was seen in Forssman glycolipid when sheep red cells were labeled with the neuraminidase/galactose oxidase/NaB3H4 method. In contrast, the increase in labeling was only about 10-40% in porcine and human globosides, which were efficiently exposed to galactose oxidase already in native red cells.

Anti-tumor properties of lymphocytes activated by the oxidizing mitogens

Human peripheral blood mononuclear cells when activated with the oxidizing mitogens, neuraminidase/galactose oxidase or sodium periodate, express cytolytic activity for freshly isolated tumor cells and for a variety of cell lines, including NK-resistant solid tumor lines. Normal lymphoid cells are not targets for cytotoxicity and do not inhibit lysis of susceptible targets mediated by the oxidizing mitogen-activated mononuclear cells. The cytotoxic response is rapidly generated and reaches peak levels at 48 hr. The oxidizing mitogens induce expression of IL 2 receptors on peripheral blood mononuclear cells. Combined treatment of cells with IL 2 and the oxidizing mitogens results in a marked enhancement of cytotoxicity. Enhancement is achieved at levels of IL 2 that alone result in minimal generation of cytotoxic cells. Growth of a human renal cancer cell line in nude mice was inhibited when the renal cancer cells were injected together with oxidizing mitogen-activated human mononuclear cells. These studies indicate that oxidizing mitogen-activated cells provide a potentially valuable source of material for the adoptive immunotherapy of tumors.

Impaired gamma interferon production by cells from patients with lymphoproliferative disorders of mature T and NK cells

We investigated interferon (IFN) production by peripheral blood mononuclear cells from four patients with chronic OKT4 T-lymphocytic leukaemia and three patients with abnormal expansions of granular lymphocytes. No spontaneous production of IFN-gamma was found in supernatants of cultures from both patients and normal controls. However, whereas the enzyme galactose oxidase or staphylococcal enterotoxin B was able to induce IFN-gamma production by normal cells, no production could be obtained in the cells under study. The possibility that this lack of production might have been attributed to an excess of N-acetylneuraminic acid masking galactose residues or to a defect of monocyte accessory cells was ruled out either by pre-treating the cells with neuraminidase or by adding normal adherent cells to the cultures, both of which resulted in a lack of production. On the contrary, the calcium ionophore A23187 (considered to act as a second specific step, following oxidation of galactose residues, toward genetic derepression of IFN-gamma) induced considerable IFN-gamma production in all the three tested patients. It can be concluded that, although in rare cases, as previously reported by other authors, cells from patients with T or NK lymphoproliferative disorders may spontaneously produce IFN-gamma, this is not a general mechanism that underlies the disease. In fact, in all our cases a defect of IFN-gamma production was found. This defect seems due to an alteration at the membrane level of the galactose-containing glycoproteins and can be restored by induction with a calcium ionophore.

Canine dendritic cells from peripheral blood and lymph nodes

Canine dendritic cells were prepared from peripheral blood or lymph nodes using a series of steps including fractionation on bovine plasma albumin (BPA), irradiation with 4000 R, incubation for 16-18 hours, and refractionation on BPA. Dendritic cells were recovered in the low density (LD) fraction containing approximately 0.6% of the unfractionated cells. Measured by the incorporation of 3H-thymidine, the response of the high density (HD) cells to neuraminidase-galactose oxidase (NGO) was lower than that of the unfractionated lymph node cells (LNC) but increased in a concentration dependent manner after the addition of a population of cells enriched for dendritic cells (30-70% by morphologic criteria). Cooperation between HD- and LD- cells was not restricted to identity of the major histocompatibility complex. Canine dendritic cells also displayed stimulatory activity higher than unfractionated peripheral blood mononuclear cells (PBMC) in a one way mixed leukocyte culture (MLC). Canine dendritic cells were nonadherent to plastic, were of low density, and remained viable and functional after irradiation. For the first time, canine dendritic cells have been identified in peripheral blood and lymph nodes and have been shown to act as accessory cells in the response of lymphocytes to NGO and as stimulator cells in a MLC.

Analysis of human T lymphocyte activation in a T cell tumor model system

The human T leukemia line Jurkat maintains functional characteristics of normal T cells in responding to inducing stimuli by the release of interleukin 2 (IL 2). Presence of a phorbol ester during stimulation eliminated the requirement for specialized accessory cells in the response to cell mitogenic agents such as the lectin concanavalin A or treatment with neuraminidase and galactose oxidase. Antibodies directed against the T cell receptor-associated antigen T3 served as efficient stimuli, especially if aided by agents that cross-link immunoglobulin, indicating that a triggering signal is received by a T cell via aggregation of its antigen receptor complex. A Burkitt lymphoma cell line, Raji, was found to selectively trigger Jurkat cells, suggesting the ability of those cells to respond to certain foreign stimuli. The Jurkat cell line has been instrumental in the purification of IL 2 and cloning of the corresponding gene. Our data suggest it can also serve as a useful model for induction of T cell responses.

Membrane events leading to interferon-gamma induction by antigens

Mitogenic induction of interferon-gamma in human peripheral blood mononuclear cells (PBMC) is prevented by enzymatic cleavage of galactose residues on the cell membrane, and by calcium depletion, suggesting that oxidation of galactose on the membrane glycoproteins and activation of a calcium flux across the membrane are critical events for interferon-gamma induction in nonspecifically stimulated human PBMC. The same experimental design has been applied to human PBMC cultures enriched of specifically sensitized lymphocytes and stimulated with the respective antigens. The results of these experiments show that also antigenic induction of interferon-gamma by purified protein derivative, tetanus toxoid, and MLR requires integrity of galactose residues and calcium intake suggesting that alteration of membrane-bound galactose and activation of a calcium flow are critical triggering events for both specific and nonspecific lymphocyte activation.

Cellular and growth factor requirements for the direct and indirect oxidative induction of interleukin 2 responsiveness in human thymocytes

Human thymocytes were separated by peanut agglutinin (PNA) into PNA+ and PNA- cell fractions, and directly oxidized by the combined action of the enzymes neuraminidase and galactose oxidase (NAGO). Such treatment resulted in the induction of interleukin 2 (IL-2) responsiveness in PNA- cells but not in PNA+ cells. The molecular basis for the poor IL-2 responsiveness of PNA+ cells resides in their inability to express sufficient amounts of IL-2 receptors in response to NAGO treatment. Irradiated oxidized PNA+ or PNA- cells are able to transmit an oxidative mitogenic signal to autologous native PNA- cells but not to PNA+ cells. Depletion of plastic adherent cells from the PNA+ subpopulation totally abolished its high potency for the indirect signal transduction, whereas accessory cell depleted PNA- cells were affected to a lesser extent. Nonspecific esterase staining indicated that human thymic macrophages/monocytes are PNA+ cells. In spite of their small number (less than 0.5% of the total thymus cells) they appear to be very active in the indirect oxidative signal transmission. Unlike the indirect system, direct oxidative mitogenesis is independent of accessory cells. Attempts to detect NAGO-dependent IL-2 receptor inducing soluble factors were fruitless and there is a strict need for cell-cell interaction for the indirect transmission of the oxidative mitogenic signal.

Dendritic cell identification in head and neck lymphoid tissue. Newly recognized cells control T-lymphocyte functions

The physiologic measurements of a subpopulation of mononuclear cells derived from head and neck lymphoid tissues are similar to those of dendritic cells are described. Dendritic cells are a subpopulation of bone marrow-derived leukocytes that were originally identified in rodents and now described in man as having central control of T-lymphocyte functions. We describe a technique for the enrichment of dendritic cells obtained from tonsils utilizing a bovine serum albumin (BSA) gradient and note that they have the light and electron microscopic appearance of dendritic cells. The measured oxidative mitogenic response and interferon-gamma production in complete leukocyte cultures was compared with BSA gradient-separated preparations. The denser cells, comprised mostly of normal appearing lymphocytes, would not undergo a mitogenic response nor produce normal amounts of interferon when stimulated unless the dendritic cell-rich, less-dense fraction, was added back. The dendritic cells derived from tonsils seem to behave as a potent accessory cell for these T-lymphocyte-associated functions.

Mitogenic properties of neuraminidase and galactose oxidase-treated lymphoblastoid cells and plasma membranes for peripheral blood lymphocytes

Generation of aldehydes on terminal D-galactose or N-acetyl-D-galactosamine residues of cell surface glycoproteins by treatment with neuraminidase and galactose oxidase (NAGO) renders some types of cells mitogenic for T lymphocytes. The cell surface molecules required for the presentation of mitogenic signals by NAGO-treated cells are unknown. We tested the mitogenic properties of NAGO-treated lymphoblastoid cell lines (LCL) and subcellular fractions as an initial step in the isolation and characterization of cell surface molecules required for stimulation. We report here that the NAGO-LCL of B cell lineage were potent stimulators, whereas the NAGO-LCL of T cell lineage were weaker and more variable stimulators of lymphocyte proliferation. T-LCL that were stimulatory in indirect stimulation did not induce a mixed lymphocyte response, whereas the B-LCL were positive in both assays. Aldehyde-bearing plasma membrane-enriched subcellular fractions, depleted of nuclear, cytosolic, and mitochondrial components, were mitogenic, and the stimulatory activity was dose dependent. The ability to induce mitogenesis was abrogated by reduction of cell surface aldehyde groups. The results indicate that lymphocyte activation, induced by NAGO-treated stimulatory cells, is a plasma membrane-associated event and does not require the metabolic activity of intact cells. Furthermore, the aldehyde moiety is required but not sufficient for presentation of mitogenic signals. The LCL provide a suitable and reproducible source for isolation and characterization of stimulatory cell surface structures.

The phosphatidylinositol response and proliferation of oxidative enzyme-activated human T lymphocytes: suppression by plasma lipoproteins

The phosphatidylinositol (PI) response and DNA synthesis of neuraminidase and galactose oxidase (NAGO)-stimulated human T lymphocytes are suppressed by low density lipoproteins (LDL). To understand the mechanism of lymphocyte activation more fully, the PI response and DNA synthesis and suppression of these events by LDL in NAGO-stimulated T lymphocytes were characterized. Between 30 min and 6 hr after NAGO stimulation, there was an increase of 32Pi incorporation into PI without increased incorporation into the phosphorylated forms of PI or into other phospholipids. DNA synthesis as determined by [3H]thymidine incorporation depended on the lymphocyte-accessory monocyte ratio and total cell density. Optimal stimulation of the PI response and DNA synthesis occurred at the same concentration of neuraminidase and galactose oxidase. While the PI response was only partially suppressed by LDL with optimal suppression at 10 to 20 micrograms of protein/ml, DNA synthesis was completely suppressed although at much higher LDL concentrations, greater than 100 micrograms protein/ml. As monocyte numbers are increased, LDL suppression of DNA synthesis is decreased. The ability of NAGO to stimulate the PI response and DNA synthesis in a similar way, and the suppression of both events by LDL, suggests the PI response is important for lymphocyte activation and proliferation. Stimulation of human T lymphocytes by oxidative mitogens, neuraminidase, and galactose oxidase caused increased phosphatidylinositol metabolism and increased DNA synthesis. Both responses were suppressed by low density lipoproteins.

Chemical reduction of oxidized human lymphocytes inhibits interleukin 2 production but not induction of interleukin 2 responsiveness

Treatment with neuraminidase (NA) plus galactose oxidase (GalOxase) does not cause stimulation of human thymocytes. However, stimulation can be achieved by addition of exogenous interleukin 2 (IL-2). The IL-2-induced stimulation was inhibited with anti-Tac antibody, indicating that NA/GalOxase-oxidized cells can serve as inducers of functional IL-2 receptors on IL-2-responding T cells. The induction of IL-2 receptors by the oxidized cells was not inhibited by subsequent reduction with borohydride, since the cells could still be stimulated with IL-2. The presence of IL-2 receptors was also confirmed by flow cytometry using indirect immunofluorescence. Peripheral blood lymphocytes can be stimulated by NA/GalOxase treatment, and the conditioned medium from this treatment can support the growth of an IL-2-dependent line. This stimulation can be inhibited with borohydride and restored with IL-2. The conditioned medium derived from the borohydride-reduced cells cannot support the growth of the IL-2-dependent line, indicating that borohydride inhibits the oxidation-induced IL-2 production. The results suggest that NA/GalOxase-oxidized sites can be modified chemically without losing the potential to induce IL-2 receptors.

Inhibition of T cell responses to alloantigens and polyclonal mitogens by Ly-5 antisera

The effects of Ly-5 alloantisera on the generation of cytotoxic T cells (CTL), on the effector phase of CTL killing, and on polyclonal mitogenesis were studied. Ly-5 antisera added at the beginning of mixed lymphocyte culture (MLC) suppressed the production of CTL in an allele-specific manner. Neither Ly-5.1 nor Ly-5.2 antisera inhibited the generation of cytotoxic effectors by Ly-5.1/Ly-5.2 heterozygous spleen cells; however, a combination of Ly-5.1 and Ly-5.2 antisera markedly suppressed the appearance of Ly-5 heterozygous CTL. Similarly, Ly-5 antisera inhibited the effector phase of CTL killing in an allele-specific manner. In addition, Ly-5 alloantisera specifically blocked concanavalin A and oxidative mitogenesis of splenocytes carrying the appropriate Ly-5 alloantigen. The results are discussed in light of a possible functional role of Ly-5 molecules in immune processes.

The role of accessory cells in polyclonal T cell activation. III. No requirement for recognition of H-2-encoded antigens on accessory cells

Highly purified murine lymph node T cells were used to test the hypothesis that polyclonal T cell activation requires the recognition of mitogen-modified major histocompatibility complex (MHC) antigens on accessory cells (AC) by the T cells. A variety of tumor cells lines, including macrophage, B and mast cell tumors, as well as thymomas, were shown to function as AC in concanavalin A-induced T cell activation, even if they expressed only one class of MHC antigens or none at all. In contrast to antigen-specific responses, where the Lyt-2+ phenotype is reportedly associated with recognition of class I MHC antigens, T cells enriched for or depleted of Lyt-2+ cells were not preferentially activated in the presence of class I- or class II-positive AC, respectively. In addition, as shown by others in the guinea pig and in the rat systems, T cell proliferation induced by oxidation of cell surface sugars is equally effective if T cells or AC are oxidized. T cell mitogens, therefore, do not seem to act by altering MHC antigens on AC, but rather by providing T cell-AC contact via their agglutinating properties.

Early mitogen-induced metabolic events essential to proliferation of human T lymphocytes: dependence of specific events on the influence of adherent accessory cells

Adherent accessory cells (AC) are required for the proliferative response of T lymphocytes to antigens and various mitogens. A current model of AC-T cell cooperation is that commitment to growth of mitogen activated T lymphocytes occurs via sequential action of IL 1 and IL 2. Initial mitogen action on T lymphocytes in the presence of AC is followed by a sequence of metabolic changes which culminate in DNA replication and mitosis. Many of these early events are critical to DNA replication. We studied several of these mitogen-induced events in experiments designed to define the specific influence of AC on T cell metabolism before initiation of DNA replication. By using human peripheral T lymphocytes depleted of AC to the extent that the proliferative response is essentially ablated, we found that the sequence of early events is divided into two phases: an early activated state in which certain events are stimulated directly by mitogen and independently of AC, and an AC-dependent state in which other events occur in mitogen-treated lymphocytes only in the presence of the numbers of AC necessary to support the proliferative response. We partially support the proliferative response. We partially characterized the nature of the metabolic activation that pulse neuraminidase-galactose oxidase treatment induces in lymphocytes in the presence and functional absence of AC. Stimulated uptake of [3H] uridine and [3H]-leucine into cellular precursor pools and incorporation into macromolecules apparently requires the presence of AC, but stimulated influx of both [3H]3-O-methyl glucose and [3H]alpha-amino isobutyric acid are independent of the presence of AC. These data suggest that stimulated influx of glucose and a certain class of essential amino acids are events of the early activated state, whereas increased RNA and protein synthesis are events of the AC-dependent state. All of these events are critical to the T cell's commitment of DNA replication and mitosis. The early activated state is consistent with AC-T cell cooperation via IL 2. It is possible that IL 2 mediates passage of IL 2 receptor-bearing T cells from the early activated state to the AC-dependent state, which then leads directly to DNA replication and mitosis.

Glycoproteins of the AKR leukaemia cell surface and their relevance to leukaemia-specific surface antigens

An attempt has been made to prepare antibodies against leukaemia-specific surface antigens by immunizing (C57 B1/6 X C3H/He)F1 mice with formaldehyde-stabilized AKR leukaemic cells. The presence of antibodies was examined by indirect immunofluorescence microscopy (IFM) and the indirect antiglobulin rosetting reaction (IARR). Galactose oxidase treatment destroyed the ability of leukaemic cells to react with antibodies prepared in the hybrid mice, an effect that was reversed by treating the enzyme-modified cells with borohydride. Analysis by immunoprecipitation and polyacrylamide gel electrophoresis of leukaemic cells, labelled by the galactose oxidase/[3H]-NaBH4 technique, indicated that a group of glycoproteins of apparent molecular weight greater than 70 000 was involved. Antibodies could be raised in AKR mice to the same group of glycoproteins by immunization with irradiated leukaemic cells or irradiated neuraminidase-treated leukaemic cells. The level of antibody raised in AKR mice had no effect on the growth of leukaemic lymphoblasts introduced subcutaneously into the host. Antibodies prepared in hybrid mice against leukaemic cells also were absorbed by lymphoid cells of pre-leukaemic 6-month-old AKR mice, indicating that contrary to previous claims in the literature antigens detected by such antisera are not related to malignancy. Hybrid mouse serum cross-reacted with antigens from purified RNA virus isolated from Abelson lymphoma, as demonstrated by the immunoelectrophoretic blotting technique. The pattern of reactivity was not appreciably altered following the absorption of antibodies directed against leukaemic cells. It is concluded that the glycoproteins detected by us may not be viral antigens but normal high molecular weight lymphoid glycoproteins with altered glycosylation patterns that are induced when the viral genomes are expressed.

The use of supernatants from neuraminidase and galactose oxidase (NAGO)-treated lymphocytes as a source of T cell growth factor

Human peripheral blood or tonsil lymphocytes produce T cell growth factor (TCGF), when activated with neuraminidase (NA) and galactose oxidase (GO). Partial purification of NAGO-TCGF on Sepharose G-100 columns gave a TCGF-active fraction within the same molecular weight range as the conventional lectin-induced TCGF (approximately 15,000 Da). Human T cells, activated in mixed lymphocyte culture (MLC) with irradiated allogeneic EB-virus transformed B-cells (LCL) could be maintained in continuous culture for several months with retained functional activities. The cells showed similar growth patterns when cultured in the presence of either NAGO-TCGF or PHA-TCGF. The growing cells were characterized by means of monoclonal antibodies. After 4 weeks of culture 98% of these were OKT3+ and 87% were also OKT8+. The cytolytic activities of the cultures were tested in cell-mediated lympholysis (CML) against allogeneic LCL as target cells, in natural cytotoxicity (NK) against K562 cells and in antibody dependent cytotoxicity (ADCC) against bovine erythrocytes. Cultures displaying one or several of these functions were obtained. The results indicate, that TCGF obtained from supernatants of NAGO-activated lymphocytes is as potent as the T cell growth promoting factor obtained by lectin stimulation. One major advantage of using NAGO-generated TCGF is that contamination with lectin is avoided.

Studies on the sequestration of chemically and enzymatically modified erythrocytes

We have developed an experimental animal model to establish the patterns of sequestration of untreated, as well as chemically and enzymatically modified red blood cells (RBC). The intraperitoneal route of transfusion provides a useful way of transferring large numbers of untreated RBC into small animals and assuring their introduction into the circulation within 24 hr. Moreover, this route "filters" some types of modified erythrocytes, eg, glutaraldehyde treated RBC. From the pattern of sequestration, the RBC in the peritoneal cavity then pass through the liver where other types of modified RBC are sequestered, eg, after trypsin, pronase, protease, or sialidase treatment. Some modified RBC show a preference for the spleen as the site of sequestration, eg, galactose oxidase or N-ethylmaleimide treated RBC. These appear in the spleen despite intraperitoneal transfusion. Relevant to this study is the observation that in the rat old RBC are sequestered both by liver and spleen, while asialoerythrocytes are sequestered by liver only. A possible reason for this difference is discussed in the text.

[Properties of Fusarium graminearum galactose oxidase]

The kinetics and action mechanism of the galactose oxidase from Fusarium graminearum were studied. pH-optimum of the enzyme activity and stability was 7.0, the activity and stability of the galactose oxidase being decreased at any other values of pH. The enzyme is destabilized at acidic pH that is connected with protonization of its ionogenic group with pK 4.7. The temperature optimum of the galactose oxidase is 35 degrees C. When studying the enzyme thermoinactivation, it was found that at temperatures below 30 degrees C the energy of activation of denaturation was about 40 kcal/mole and at temperatures ranging from 30 to 70 degrees C - 13 kcal/mole. On the basis of the data obtained it was concluded that a low-temperature form of the galactose oxidase, possessing a higher energy of activation of denaturation, is more active than a high-temperature form. The value of Km for the enzyme in respect to galactose was 0.19 M, and the value of Vmax = 360 mumole/min per g of the preparation.

Cellular and growth factor requirements for activation of human T lymphocytes by neuraminidase and galactose oxidase-treated lymphoid cells

Proliferation of peripheral blood mononuclear leukocytes (PBL) can be stimulated by irradiated autologous PBL that have been treated with neuraminidase and galactose oxidase (NAGO). We determined the types of cells that stimulate and respond by isolating populations of cells enriched for macrophages, B lymphocytes, and T lymphocytes. With PBL as responding cells, proliferation was stimulated by irradiated, NAGO-treated cells with the following hierarchy: macrophage greater than PBL greater than B cells greater than T cells. Irradiated NAGO-treated macrophages and PBL induced proliferation of isolated T cells greater than or equal to the proliferation they stimulated in PBL, indicating that T cells are the predominant responding cell type. Irradiated, NAGO-treated B cells or T cells were weak stimulators of isolated T cell proliferation when compared to their ability to stimulate PBL. The ability of irradiated NAGO-treated B cells or T cells to stimulate isolated T cell proliferation was greatly enhanced by the addition of untreated macrophages or by the addition of conditioned media from mitogen-activated PBL. Biologic, biochemical, and biophysical characterization of the conditioned media revealed it contained both lymphocyte polypeptide growth factors, interleukin 1 and interleukin 2. Semipurified preparations of either of these growth factors were capable of enhancing T cell proliferation stimulated by irradiated NAGO-treated B or T cells. These data indicate T cell proliferation induced by irradiated, NAGO-treated cells requires the aldehyde-bearing cells for the induction of soluble growth factor production and for the induction of putative membrane receptors for these growth factors.

On the mechanisms of inhibition of lymphocyte mitogenesis by high conA concentrations

ConA at high concentrations inhibits lymphocyte mitogenesis. Previous studies have shown that inhibitory conA concentrations do not inhibit the acquisition of responsiveness to interleukin-2 (IL-2) when excessive conA is removed. To analyse further the problem of high-dose inhibition by conA, we determined whether inhibition of mitogenesis is related to inhibition of IL-2 production or, alternatively, whether factor production is intact, but the cells are rendered incapable of responding to the factor. ConA stimulates IL2 production at concentrations that are inhibitory to mitogenesis of human lymphocytes. IL-2 was assayed both in a murine cytotoxic T cell line and human memory cells. The response of IL-2-dependent cells to Il-2-containing medium was, on the other hand, inhibited by conA in a dose-dependent fashion. One mechanism whereby high conA concentrations inhibit mitogenesis is by rendering cells resistant to IL-2, possibly via extensive cross-linking of cell surface sites.

Binding of Leishmania promastigotes to macrophages

Leishmania tropica promastigotes are easily attached to and engulfed by C3H peritoneal macrophages in vitro at 37 degrees C. Different sugars at 0.3-0.5 M inhibited in vitro the attachment of L. tropica promastigotes to C3H peritoneal macrophages with lactose (Gal-beta [1 leads to 4]Glc) being the most efficient. Inhibition of attachment is also affected by pre-treatment of promastigotes with galactose oxidase. Oligosaccharides extending from promastigote and amastigote cell surfaces contain an important proportion of non-reducing galactose as does the carbohydrate-rich factor (EF) excreted by promastigotes of L. tropica and L. donovani. This study suggests that Leishmania, an obligatory intracellular parasite, uses as a means of entering the host cell a cellular mechanism similar to that used in the removal of damaged cells from blood circulation. This mechanism is assumed to take advantage of the exposed sugars, particularly the exposed non-reducing galactose, on the parasite surface during the stage of attachment. Once the parasite is inside the cell, the EF it produces might have a protective function, being inhibitory to some of the host cell lysosomal enzymes.