The effect of neuraminidase on the fate of transfused lymphocytes

Activated T-lymphocytes express class I molecules which are hyposialylated compared to other lymphocyte populations

Various H-2 and Qa/Tla region encoded class I glycoproteins expressed on the surface of resting and activated T- and B-lymphocytes were compared by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). The isoelectrophoretic patterns of the H-2K, H-2D, Qa-2 and Qa-1 molecules isolated from activated T-lymphocytes were more isoelectrically heterogeneous and/or possessed species with a more basic pI than the same molecules isolated from resting T- and B-cells or activated B-lymphocytes. The differences in charge heterogeneity of class I molecules between activated T-cells and the other cell subpopulations were abolished by treatment with: (1) endoglycosidase F which removes N-linked oligosaccharides from glycoproteins, and (2) neuraminidase which removes sialic acids from carbohydrate side chains. Thus, the increased charged heterogeneity of class I molecules expressed by activated T-cells is due to altered sialylation of their N-linked oligosaccharides. These results indicate that a mechanism exists, upon activation of T-lymphocytes, for alteration (desialylation) of the carbohydrate moieties of class I molecules.

Sulphated polysaccharides, corticosteroids and lymphocyte recirculation

Intermediate lymph was collected from the efferent duct of a single, superficial lymph node in unanaesthetised sheep for a few days before and after they were given an intravenous (i.v.) injection of a sulphated polysaccharide, fucoidan, at a dose of 10 mg per kg. Within an hour or so of the injection, the recirculation of lymphocytes through the node under study fell by over 80% and remained low for a few hours. This acute reduction in lymphocyte recirculation could be duplicated almost exactly by giving an i.v. dose (250 micrograms per kg) of a synthetic corticosteroid, dexamethasone, instead of fucoidan. Also, during the fall in lymphocyte recirculation that followed the injection of fucoidan, the concentration of cortisol in the blood plasma increased nearly 10-fold. These findings strongly suggest that much of the effect of exogenous sulphated polysaccharides on the recirculation of lymphocytes is neither direct nor specific, but secondary to an increased secretion of corticosteroid hormones.

Aberrant lymphocyte trafficking in murine systemic lupus erythematosus

The patterns of migration of lymphoid cells from autoimmune-prone MRL-lpr/lpr, C57BL/6-lpr/lpr, MRL-+/+, and NZB mice were compared to those from sex and age-matched, normal CBA, C57BL/6, and BALB/C mice. Chromium-51-labelled spleen and lymph node cells from all autoimmune mice tested homed preferentially to the spleen relative to lymph node of the recipient strain. The data indicate that defects in lymphocyte trafficking are widespread in murine lupus and suggest a role for abnormal lymphocyte migration in the pathogenesis of this disease.

Activation of T lymphocytes results in an increase in H-2-encoded neuraminidase

The endogenous neuraminidase activity of various mouse lymphoid subpopulations and tissue compartments was examined by a sensitive fluorometric assay. These analyses indicated that activated T lymphocytes possessed a significantly higher level of intracellular neuraminidase than activated B or resting T or B lymphocytes. Examination of the level of neuraminidase in bone marrow, thymus, lymph node, and unfractionated spleen indicated that these lymphoid tissues contained significantly less neuraminidase than was detected in stimulated T cells. Kinetic studies revealed that the majority of the increase in neuraminidase activity occurred between 24 and 48 h following stimulation. Analysis of activated T lymphocytes prepared from a panel of inbred mouse strains indicated that cells from mice of the H-2v haplotype, which possess the Neu-1a allele and are deficient in liver neuraminidase, exhibited a level of activity which was significantly lower than that detected in stimulated T cells from other mouse strains. These results indicate that the endogenous neuraminidase activity of T lymphocytes increases upon stimulation, and that the level of this enzyme activity in lymphoid cells is also controlled by the Neu-1 locus, which is located in the H-2 region of the major histocompatibility complex.

Studies on the liver sequestration of lymphocytes bearing membrane-associated galactose-terminal glycoconjugates: reversal with agents that effectively compete for the asialoglycoprotein receptor

The removal of "effete" glycoproteins from the circulation represents a proposed physiologic role for the hepatocyte asialoglycoprotein receptor. Our experiments support the hypothesis that this receptor may also be directly involved in the removal from the circulation of cells bearing asialoglycoconjugates. We report that the enhanced liver localization of neuraminidase-treated lymphocytes can be competitively inhibited by the coinjection of asialofetuin (ASF). Fetuin itself was without effect. Competitive inhibition of the liver receptor allowed normal localization to lymphoid tissues of the enzyme-treated lymphocytes, a condition which persisted as long as free ASF was present in the circulation. Our studies support the concept that cell surface carbohydrates play an important role in the tissue distribution of circulating lymphocytes. The process of thymocyte maturation, bone marrow transplantation, and the adoptive immunotherapy with continuous T-cell lines represent conditions where recirculation potential may be influenced by the presence of galactose terminal glycoconjugates.

Nonmetastatic tumor cells acquire metastatic properties following somatic hybridization with normal cells

Somatic cell hybridization between nonmetastatic tumor cells and normal cells of the lymphoreticular system results in hybrid cells manifesting metastatic properties of defined target organ specificity. Thus, fusion of the nonmetastatic BALB/c originated NSI plasmacytoma with C57BL B lymphocytes resulted in hybridomas, each of which were metastatic. Of 10 hybridomas, 7 generated metastases in the spleen and liver, whereas 3 generated liver metastases. The generation of liver metastases by hybridomas which homed to both spleen and liver, but not by those which homed to the liver only, was controlled by the spleen. The acquisition of metastatic properties via somatic cell fusion seems to represent a general principle, in which the normal partner determines the target organ specificity for the metastatic growth. Thus, fusion of SP2/O myeloma cells with syngeneic B lymphocytes also resulted in a hybrid cell metastasizing to the spleen and liver, yet a somatic hybrid between NSI and a macrophage or dendritic-like cell metastasized to the lung. Cell surface molecules encoded by the genome of the normal partner was demonstrated to control the target organ specificity: antibodies against MHC-encoded antigens of the normal B cell partner prevented the generation of metastases by hybridomas metastasizing to the spleen and liver, but not by those metastasizing to the liver only. This is in accordance with the function of MHC molecules on lymphocytes in controlling their homing to lymphoid organs. Hybridomas of T cell lymphomas also manifested metastatic properties. Analysis of the cell surface Thy-1 antigens of a hybridoma (DCH10), produced via somatic fusion between BW5145 lymphoma and a putative macrophage cell indicated that cells of liver metastases (DCH10-Li) generated by the hybrid cells might have undergone further somatic cell fusion in vivo with host (T?) cells. These cells have acquired new metastatic properties, generating metastases in spleen, liver and kidneys. In fact, even the inoculation of the parental BW lymphoma cells resulted in a case of liver metastasis (BW-Li). Such BW-Li cells, upon reinoculation, also generated metastases in the spleen, liver and kidneys. Analysis of the Thyl phenotype indicated that BW-Li cells may also have undergone somatic cell fusion in vivo with host (T?) cells, resulting in the acquisition of metastatic properties. The pattern of cell-cell interactions (adhesion, infiltration) with liver cell monolayers of BW-Li cells and of DCH10-Li (T-cell lymphomas) was identical, and differed from cells of liver metastases of the myeloma-B cell hybridomas which might be based on responses to liver growth signals.(ABSTRACT TRUNCATED AT 400 WORDS)

Subsets of epidermal Langerhans cells as defined by lectin binding profiles

In this study we characterize the cell surface glycoconjugate moieties of strain 2 guinea pig epidermal Langerhans cells (LC) in single cell suspension by using a battery of 17 fluorescent lectins. All LC displayed binding sites for concanavalin A, succinylated concanavalin A, Lens culinaris agglutinin, Pisum sativum agglutinin, wheat germ agglutinin, succinylated wheat germ agglutinin, Griffonia simplicifolia agglutinin I, Ricinus communis agglutinin I, Phaseolus vulgaris E agglutinin, and Phaseolus vulgaris L agglutinin, but failed to bind Sophora japonica agglutinin (SJA), Dolichos biflorus agglutinin (DBA), and Ulex europaeus agglutinin I (UEA I). Neuraminidase pretreatment rendered LC reactive for SJA, but not for DBA and UEA I. The binding profiles of certain lectins point to the existence of LC subpopulations in that Griffonia simplicifolia I-B4 isolectin, peanut agglutinin (PNA), Helix pomatia agglutinin, and soybean agglutinin bound to only 80% (range 70-90%) of Ia-positive epidermal cells; binding sites for these lectins on primarily unreactive Ia-positive cells were unmasked when epidermal cells were treated with neuraminidase prior to lectin labeling. Ultrastructural PNA labeling studies revealed that the vast majority of Birbeck granule-containing LC displayed PNA binding sites, whereas indeterminate cells were consistently PNA-negative. Identification of carbohydrate configurations expressed on LC surfaces by lectin binding may provide a clue for the elucidation of the mechanisms of established LC functions and possibly the discovery of as yet unknown properties of this cell type.

Isolation and characterization of type III group B streptococcal mutants defective in biosynthesis of the type-specific antigen

Four classes of mutants of type III group B streptococcus were isolated by serial subculture of the wild-type strain in the presence of type III-specific rabbit antiserum. Class I mutants no longer synthesized sialic acid but still elaborated the core antigen. Class II mutants maintained the ability to synthesize sialic acid but could not attach it to the core antigen. Class III mutants did not produce the core antigen but still synthesized intracellular sialic acid. Class IV mutants synthesized the complete antigen; however, only approximately 4% of the antigen synthesized was found associated with the cell wall peptidoglycan (in the wild-type strain greater than 85% of the antigen synthesized is covalently attached to the cell wall peptidoglycan), whereas greater than 90% of the antigen was secreted into the growth medium. Production of other components (CAMP factor, group B antigen, beta-hemolysin, neuraminidase) by these mutants appeared similar to those of the wild-type strain. Mouse lethality studies of these strains indicated that all four classes have greater than 3 log10-higher 50% lethal dose values than that of the wild-type strain. To understand the basis for this variation, the invasive ability of the wild-type strain and the sialic acid-deficient mutant strain M-10 (class I) was examined. Mice received 10(5) CFU of each organism; they were then sacrificed at various times postinoculation, and viable group B streptococci from different organs were enumerated. Mice were able to clear M-10 more efficiently, with greater than 80% of M-10 cells being phagocytized by macrophages within 1 h, whereas the wild-type strain was able to evade phagocytic killing and disseminate to other tissues. These data, therefore, strongly indicate that the sialic acid moiety greatly enhances the virulence of the type III antigen. In addition, the level of cell-associated type-specific antigen appears to contribute significantly to the pathogenicity of the organism.

Effect of enzymic removal of cell surface constituents on metastatic colonisation potential of mouse mammary tumour cells

Trypsin treatment of viable cells from 24 spontaneous murine mammary carcinomas resulted in a mild but reproducible diminution in their capability to colonise the lung after i.v. reinoculation but did not alter the distribution of deposits formed. The effects were similar on tumours of high and of low colonisation potentials. Neuraminidase and hyaluronidase did not exert any effect on metastatic colonisation potential, although all 3 enzymes were shown to be active and specific in cleaving their purified substrates, under the conditions in which they were used on the cells. Trypsin and neuraminidase were also shown to release characteristic components from the surfaces of living tumour cells, although hyaluronidase did not release detectable quantities of N-acetyl glucosamine indicating that there is little hyaluronic acid-related mucopolysaccharide on the surface of these mammary tumour cells. The results provide direct evidence suggesting that surface protein composition exerts an effect on the metastatic colonisation capability of mammary tumour cells.

A rapid and sensitive assay for neuraminidase using peanut lectin hemagglutination: application to Vibrio cholera and Trypanosoma cruzi

A neuraminidase assay based on peanut lectin agglutination is described. Human red blood cells are used both as substrate for the enzyme and as probe for the lectin. The validity of the method is ascertained by measuring the enzyme and lectin activities on erythrocytes whose outer membrane sialic acid was labeled with tritium after oxidation with sodium periodate followed by reduction with sodium borotritiide. The neuraminidases of Trypanosoma cruzi and Vibrio cholera are used as examples; in both cases, a linear relationship is observed between the degree of erythrocyte desialylation and the peanut hemagglutination titer. For the hemagglutination assay, lectin in homogeneous form as well as in crude peanut extracts may be used, and free sialic acid need not be separated from substrate-bound sialic acid. The hemagglutinating activity of peanut lectin is not affected by pre-treatment of the erythrocytes with various proteases. The method is particularly useful in the neuraminidase analysis of multiple samples, such as in gel filtration chromatography and for screening of hybridoma antibodies against neuraminidase.

Neuraminidase production by a Streptococcus sanguis strain associated with subacute bacterial endocarditis

The properties of an extracellular neuraminidase produced by a Streptococcus sanguis strain (isolated from a confirmed case of subacute bacterial endocarditis) during growth in a defined medium was examined in this investigation. This enzyme, isolated from concentrated culture supernatants of S. sanguis biotype II, was active against human alpha-1 acid glycoprotein, N-acetylneuramin lactose, bovine submaxillary mucin, and fetuin. Neuraminidase production paralleled bacterial growth in defined medium and was maximal in the early stationary phase of growth but decreased dramatically, probably owing to protease production, during the late stationary phase. The enzyme was purified to near homogeneity by a combination of salt fractionation, ion-exchanged chromatography on DEAE-Sephacel, and gel filtration on Sephadex G-200. These procedures yielded an enzyme preparation that possessed a specific activity of 174.4 mumol of sialic acid released per min per mg of protein against human alpha-1 acid glycoprotein. The Km value for this enzyme with human alpha-1 acid glycoprotein as substrate was 2.5 X 10(-3) M, and the enzyme possessed a pH optimum of 6.5. The S. sanguis neuraminidase had a molecular weight of approximately 85,000 as estimated by gel filtration and approximately 90,000 when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was stable at temperatures of 4 and 37 degrees C for 3 h, but approximately 50% of the enzymatic activity was lost within 30 min at 50 degrees C, with 100% of the enzymatic activity being destroyed within 10 min at temperatures of greater than or equal to 65 degrees C.

The role of accessory cells in polyclonal T cell activation II. Induction of interleukin 2 responsiveness requires cell-cell contact

It has previously been reported (Hünig, T. et al., Eur. J. Immunol. 1983. 13:1) that highly purified peripheral T cells do not respond to concanavalin A (Con A) even in the presence of Con A-induced spleen cell supernatant as a source of interleukin 2 (IL 2). In the present report, the hypothesis was tested whether this unresponsiveness correlates with the observed inability of Con A to mediate cell-cell contact between highly purified T cells. It was found that T cells, pretreated with neuraminidase to reduce their net negative charge, were both aggregated and rendered IL 2-reactive by Con A. In addition, leukoagglutinin (LA) was found to be able to both agglutinate untreated T cells and to make them IL 2-reactive. Neuraminidase treatment reduced the concentration of LA required to mediate both effects. Neuraminidase treatment did not alter the overall Con A-binding capacity of T cells, nor did it induce reactivity to IL 2 in the absence of lectin. Furthermore, irradiated, neuraminidase-treated T cells served as accessory cells (AC) in the induction of responsiveness to IL 2, but not for production of IL2, which depends on Ia+ AC. Finally, Lyt-2- neuraminidase-treated peripheral T cells responded in the same fashion as whole T cell populations, indicating that at least some T cells of the helper phenotype need not interact with Ia+AC for the induction of IL 2 responsiveness.

A developmentally regulated neuraminidase activity in Trypanosoma cruzi

The human pathogen Trypanosoma cruzi (Y strain) contains a neuraminidase activity that varies widely in the different developmental stages of the parasite. The specific neuraminidase activity of infective trypomastigotes obtained from tissue culture and from the bloodstream of infected mice is 7 to 15 times higher than that of the acellular culture forms. Amastigotes were devoid of enzyme activity. The enzyme has a pH optimum of 6.0 to 6.5. Live trypanosomes released sialic acid from human erythrocytes and plasma glycoproteins. Several sialyl compounds were hydrolyzed by the parasite, but the best substrate was the protein orosomucoid. Erythrocytes from infected mice with T. cruzi parasitemia were agglutinated by peanut lectin and the hemagglutination titer was correlated with the degree of parasitemia.

Germinal center B cells lack homing receptors necessary for normal lymphocyte recirculation

Germinal center B cells (GCLC) are a discrete population of antigen-activated lymphoblasts that lack surface IgD and express abundant cell surface binding sites for peanut agglutinin (PNA). These phenotypic features render GCLC easily distinguishable from nearly all plasma cells, T cells, and unstimulated B cells, and have enabled us to identify and isolate GCLC from antigen-stimulated murine lymphoid organs. We have examined the migratory properties of these lymphoblasts in (a) short-term in vivo homing studies, and (b) an in vitro assay of lymphocyte binding to post-capillary, high endothelial venules (HEV) in frozen sections of Peyer's patches and peripheral lymph nodes. In the in vivo experiments, intravenously injected GCLC failed to migrate in significant numbers to peripheral lymphoid organs in comparison with T cells or IgD+ B cells. In the in vitro binding assay, GCLC did not adhere to HEV in either Peyer's patch or peripheral node sections. A variety of factors, such as preferential sequestration in the liver, may operate in vivo to influence the localization of these cells. However, their nearly total failure to migrate into lymphoid organs can best be explained by their inability to recognize and adhere to the specialized HEV which normally mediate the emigration of recirculating lymphocytes from the blood into these sites. The concept that GCLC fail to express functional homing receptors for HEV has been further supported by studies using MEL-14, a monoclonal antibody that appears to recognize the lymphocyte surface receptor for peripheral node HEV: In contrast to most peripheral lymphocytes, GCLC fail to bind MEL-14. These migratory and endothelial-recognition properties of GCLC, when viewed in the context of the possible role of these cells as precursors of plasma cells and/or memory B cells, have led us to propose that the inability of GCLC to recognize HEV may be transient and related to a phase of sessile B cell differentiation.

Properties of endogenous, membrane-associated sialidase activity (N-acetylneuraminidase) of the goldfish visual system

The endogenous sialidase (N-acetylneuraminidase) activity of membranes prepared from goldfish retina and optic tectum displays characteristics similar to those reported for neural plasma membrane sialidases of other organisms. Endogenous membrane sialidase activity was found to be optimal at ph 4.0, and maximal release was obtained at 37-50 degrees C, above which temperature thermal instability of the preparations was observed. Optic nerve crush, which results in regeneration of retinal ganglion cell axons, did not result in significant changes in measured endogenous membrane sialidase activity in either the retina or the optic tectum. Enzymatic hydrolysis of membrane sialoglycolipid (ganglioside) accounted for about 70% of the total sialic acid released. Ganglioside GM1 accumulated as the major lipid product in both retina and tectum, indicating that the inner sialosylgalactosyl linkage in the ganglio oligosaccharide series was resistant to hydrolysis by the endogenous enzyme.

The effect of vitamin A depletion on antigen-stimulated trapping of peripheral lymphocytes in local lymph nodes of rats

The effect of vitamin A depletion on antigen-stimulated trapping of peripheral lymphocytes in lymphatic organs was studied in rats. Distribution of [3H]-uridine-labelled syngenic peripheral lymphocytes was quantified by assaying radioactive content of brachial and axillary lymph nodes, spleen and liver of normal and vitamin A-depleted F344/Ducrj rats immunized with sheep red blood cells. Localization of labelled cells in the ipsilateral brachial lymph nodes of the normal rats was stimulated by three times upon immunization with sheep erythrocytes as compared with the contralateral nodes. Recruitment of cells in axillary lymph nodes, spleen and liver was not significantly different from non-immunized values. The vitamin A-depleted rats exhibited marked deterioration in antigen-stimulated trapping of labelled cells in the draining brachial lymph nodes. These results suggest that this effect of vitamin A depletion is due to derangement of integrity of lymphocyte-trapping mechanism in the draining lymph nodes and not to any change in nature of lymphocytes per se.

Cell-type-related segregation of surface galactosyl-containing components at an early developmental stage in hemopoietic bone marrow cells in the rabbit

The avidin-biotin complex was used for the selective ultrastructural labeling of terminal cell surface galactosyl residues. Rabbit bone marrow cells were treated with the enzyme galactose oxidase in the presence of biotin hydrazide. Subsequent treatment with ferritin-avidin conjugates enabled the electron microscopic visualization of terminal membrane-based galactose and/or N-acetylgalactosamine on these cells. All stages of erythroid development were characterized by high levels of exposed cell surface galactose, whereas all leukoid cells in the same preparations were virtually unlabeled by the above method. Modulations in the distribution of these surface determinants during differentiation and maturation of rabbit erythroid cells were found to concur in inverse fashion with respect to that of terminal sialic acids. Neuraminidase treatment, before the above labeling procedure, resulted in the exposure of additional galactosyl residues on the surface of all bone marrow cell types. The results indicate that a galactose-bearing glycoconjugate(s) may comprise an erythroid-specific membrane constituent of rabbit bone marrow cells. The high density of galactose on the surface of even the earliest erythroid precursors may eventually enable the identification and isolation of a stem cell, which already contains the erythroid-specific galactoconjugate(s). The results suggest that variations in the spectrum of cell surface carbohydrates may serve as recognition signals in the complex set of intercellular interactions which occur during the development and maturation of the erythrocyte. The occurrence of similar but species-specific variations in the complement of surface heterosaccharides during erythroid development of humans and other mammals supports this contention.

Isolation and characterization of two individual glycoprotein components from human milk-fat-globule membranes

Two individual glycoprotein components from human milk-fat-globule membranes (MFGM) has been purified by selectively extracting the membrane glycoproteins followed by lectin affinity chromatography and gel filtration on Sephadex G-200 in the presence of protein-disaggregating agents. The purified glycoprotein components, termed 'epithelial-membrane glycoprotein' (EMGP-155 and EMGP-39) have estimated molecular weights of 155 000 and 39 000 respectively, and yield a single band under reducing conditions on sodium dodecyl sulphate/polyacrylamide gel. EMGP-155 and EMGP-39 contain 21.0% and 7.0% carbohydrate by weight, with fucose (13.5%, 12.4%), mannose (3.7%, 6.2%), galactose (28.5%, 22.6%), N-acetylglucosamine (17.8%, 7.4%) and sialic acid (36.4%, 51.4%) of the carbohydrate moiety respectively. For both the glycoprotein components, aspartic and glutamic acid and serine are the major amino acid residues.

Redistribution of renal allograft-responding leukocytes during rejection. II. Kinetics and specificity

We investigated the traffic of allograft-responding leukocytes between the host and graft without handling of these cells in vitro. The blood flow between the host and graft was disconnected, the proliferating cells were labeled with [3H]thymidine selectively in the graft or in the host, the label was chased with cold thymidine, and the circulation was reestablished. The localization of labeled cells was quantitated by autoradiography. The first host-derived labeled cells appeared in the graft and graft-derived labeled cells in the host, already on the 1st d after transplantation. This was followed by an exponential increase in the labeled cell traffic in both directions. The peak of traffic was observed on day 4 after transplantation, whereafter the traffic rapidly declined and tapered off. This decline was not due to exhaustion of supply, as the labeled cells continued to proliferate in their original compartments, nor to a slowdown of blood circulation, which took place 2-3 d later. We consider the decline to indicate that the rejection has proceeded to a (irreversible) stage autonomous of the host lymphatic and hematopoietic system. During the exponential increase, nearly one-third of the graft-infiltrating inflammatory cells were replaced as a consequence of relocalization during each 18-h-period. All mononuclear white cell types, with the exception of granulocytes, participated in the traffic. Most lymphoid cells entrapped in the graft were descendents of recent cell divisions; most of the mononuclear phagocytes derived from a preexisting phagocyte pool. The entrapment of labeled leukocytes in a relevant graft was specific: when an allograft and an autograft were simultaneously transplanted, a more than 50-fold entrapment was observed in the allograft, compared with the autograft. Very few of the cells localized in irrelevant positions, such as the liver and lung, of the recipient.

The role of the liver in clearance of glycoproteins from the general circulation, with special reference to intestinal alkaline phosphatase

Glycoproteins represent a wide variety of macromolecules with important physiological functions. Characteristic variations in carbohydrate composition and plasma concentration of these proteins may occur during pathological conditions. Steady-state plasma concentrations are determined by release from normal or diseased tissues and simultaneous clearance from the general circulation. The liver occupies a central position in the production but also clearance and catabolism of such glycoproteins. A number of specialized receptor-mediated transport processes for different types of glycoproteins in this organ is reviewed. Membrane recognition is generally followed by absorptive endocytosis and vesicle transport to lysosomes, Golgi system and/or bile canaliculis. The charge of the protein, the nature of the terminal sugar residue or complex formation with other glycoproteins may determine the extent of uptake in the various cell types of the liver. By means of these transport processes the liver is able to remove potentially dangerous macromolecules such as denatured proteins, aggressive enzymes and immunocomplexes from the general circulation. Drugs can bind to some of these proteins or may interact with the hepatic transport or catabolism processes. Special attention is paid to the hepatic clearance of asialoglycoproteins with terminal galactose groups. Intestinal alkaline phosphatase is used as a model compound to characterize the pharmacokinetic profiles of hepatic uptake and biliary excretion in the rat in vivo and isolated perfused rat livers. Histochemical and electron-microscopic studies demonstrated a galactose-specific, receptor-mediated endocytotic process, mainly but not exclusively localized in centrolobular hepatocytes. Drug interactions with these processes will be the subject of further investigations.

Effect of influenza virus on phagocytic cells

Many viral infections predispose to bacterial superinfection, and it has been suggested that the increased susceptibility to bacterial infections is at least in part due to the effect of virus on the phagocytic cell function. Since the mechanisms by which the viruses affect neutrophil function are not well understood, we studied the function of polymorphonuclear leukocytes (PMNs) after incubation with influenza virus. Phagocytosis was assayed by incubating influenza virus (strain type A-Texas-77 [H2N2] ) treated leukocytes with 3H-thymidine-labelled staphylococci. The oxidative metabolism of the PMNs was studied by measuring the chemiluminescence generated by virus-treated PMNs after incubation with zymosan. Chemotaxis was measured under agarose. After incubation with 10(7) EID50 units of influenza virus, PMNs ingested only 35% of the bacteria, whereas control leukocytes ingested over 80%. Influenza virus also reduced the mobility of the PMNs and markedly suppressed the generation of chemiluminiscence. UV-killed virus with intact neuraminidase produced similar effects but virus with heat-inactivated neuraminidase did not. Virus envelope-neuraminidase may be responsible for some of the effects of the virus on the PMNs.

Increase of the in vitro complement-dependent cytotoxicity against autologous invasive human bladder tumor cells by neuraminidase treatment

Complement-dependent cytotoxicity (CDC) was measured in a 51-Cr release assay against tumor cells from 13 non-invasive and 7 invasive transitional-cell tumors of the urinary bladder. CDC was compared between mechanically dispersed tumor cells and neuraminidase-treated tumor cells. Neuraminidase treatment of bladder tumor cells enhanced their susceptibility to complement-dependent cytolysis. There were no differences in CDC between autologous and allogenic sera. Mechanically dispersed tumor cells showed no significant differences in susceptibility when non-invasive and invasive tumor cells were compared, whereas significant differences in CDC were seen when neuraminidase-treated non-invasive and invasive tumor cells were used as targets. A C2 deficient serum showed significantly reduced cytotoxicity suggesting that the CDC reaction requires classical complement activation. A hypogammaglobulinemic serum showed stronger CDC compared to autologous and other allogenic sera and upon dilution of autologous sera and hypogammaglobulinemic serum CDC declined parallelly.

Carbohydrate complexity of the mouse thymocyte Thy-1 glycoprotein as demonstrated by lectin affinity and isoelectric focusing

The Thy-1 glycoprotein of mouse thymocytes was analysed with regard to the properties of its carbohydrate part. Of the different lectins tested, partial binding of Thy-1 from membrane extracts was found to Lens culinaris agglutinin (approximately 50%) and wheat germ agglutinin (approximately 25%). In contrast, concanavalin A bound all Thy-1. The results indicate that there is considerable microheterogeneity in the oligosaccaride chains within the Thy-1 population. Thy-1 was purified from thymocyte membrane extracts by concanavalin A affinity chromatography and gel filtration. The purified preparation revealed, on analysis by isoelectric focusing, at least six charge variants (isoelectric points ranging from approximately 5-9). These variants were isolated, treated with neuraminidase and tested for lectin binding and isoelectric point. It was shown that the charge heterogeneity was due to different amounts of sialic acid; even the most basic form contained at least one sialic acid residue. Furthermore, it was concluded that the degree of sialylation was not correlated to the lectin-binding properties. Analysis of Thy-1 from surface 125I-labelled thymocytes showed that the purified preparation was representative in its complexity of the Thy-1 glycoprotein exposed on the surface membrane. The possible biological implications of the findings are discussed.

Sialyltransferase activity in leukemia

Sialyltransferase activity in blasts from acute lymphoblastic leukemia (ALL) was markedly lower (1.68 +/- 1.23 pmol/mg protein) than those (6.18 +/- 2.22 pmol/mg protein) of lymphocytes from normal volunteers (t less than 0.001). On the contrary, enzyme activity was significantly increased in blasts (1.21 +/- 0.38 pmol/mg protein) from acute non-lymphoblastic leukemia, compared to the level (0.53 +/- 0.32 pmol/mg protein) of mature granulocytes (t less than 0.001). In TdT-negative CML in blast crisis, sialytransferase activity (2.11 +/- 0.88 pmol/mg protein) was significantly higher than those of mature granulocytes (t less than 0.001), whereas no significant difference in the enzyme activity was noted between the blasts from TdT-positive CML in blast crisis and from ALL. In TdT-positive ALL cases, there was an inverse relationship (r = -0.85, t less than 0.01) between sialytransferase activity and terminal deoxynucleotidyl transferase (TdT) activity of the blasts. Therefore, sialytransferase in leukocytes may be a unique enzyme in which changes in activity relate to the differentiation or malignant transformation of leukocytes.

Lectin mediates homing of sialidase-treated erythrocytes of the liver as revealed by scintigraphy

Mammalian erythrocytes loose their normal circulatory pattern following desialylation by sialidase and are trapped in the liver. The mechanism responsible for this phenomenon has been studied by a new scintigraphic method. We report here that the retention of asialo-erythrocytes in the liver is due to the interaction between a lectin-like receptor on Kupffer cells and terminal D-galactosyl residues exposed on erythrocytes after sialidase treatment. The major findings supporting the conclusion are: First, kinetics of asialo-erythrocyte accumulation in the liver are identical in conventional and germfree animals, demonstrating that the presence of serum antibody is not essential. Second, trapping of asialo-erythrocytes can be substantially inhibited by intravenous injection of N-acetyl-D-galactosamine or galactosylated bovine serum albumin, other saccharides or glycoproteins are less or not at all effective. This specificity pattern is characteristic for the D-galactose-specific lectin on Kupffer cells. It therefore appears that the retention of sialidase-treated erythrocytes in the liver is lectin- and not antibody mediated.

Involvement of membrane galactose in the in vivo and in vitro sequestration of desialylated erythrocytes

The influence of terminal beta-galactose residues for the in vitro and in vivo sequestration of sialidase-treated erythrocytes by macrophages was investigated. Preincubation of rat peritoneal macrophages with galactose, oligosaccharides, glycoproteins and glycolipids with terminal beta-galactose residues inhibits both binding and phagocytosis of sialidase-treated erythrocytes by masking a beta-galactose-specific lectin on the macrophage cell membrane. These inhibition studies show that binding via demasked erythrocyte surface beta-galactosyl residues to this lectin is necessary for the subsequent phagocytosis step. According to these observations, repeated injections of lactose (30mM serum concentration) and asialo-fetuin (10-30 microM serum concentration) into the blood stream of rabbits led to a reduction of the rapid sequestration rate of sialidase-treated erythrocytes. Asialo-fetuin proved to be a much more potent inhibitor than lactose, in accordance with the in vitro experiments. This inhibition is reversible, as after the disappearance of the inhibitory effect, the sialidase-treated erythrocytes were again rapidly removed from the circulation to an extent similar to that of the experiments without inhibitors. No significant influence on binding and phagocytosis was measured in the presence of sialyllactose and native fetuin in vitro, or of native fetuin on sequestration in vivo. The experiments with rabbits show that a beta-galactosyl-specific lectin seems to be involved in the mechanism of sequestration of desialylated erythrocytes in vivo, as has been observed in vitro with rat peritoneal macrophages.

Carbohydrate surface constituents of T cells mediating delayed-type hypersensitivity that control entry into sites of antigen deposition

Peritoneal exudate T lymphocytes (PETLs) that mediate delayed-type hypersensitivity (DTH) to sheep red blood cells in mice were modified by in vitro treatment methods which modify surface carbohydrate constituents. Neuraminidase treatment resulted in the release of both N-acetylneuraminic acid and N-glycolyl-neuraminic acid, and periodate treatment in the formation of the corresponding C7 analogues. Treatment of PETLs with neuraminidase led to a transient reduction of DTH reactions in syngeneic cell recipients. After treatment with neuraminidase plus galactose oxidase, adoptive mediation of DTH was more markedly reduced. Incubation of PETLs with periodate caused a permanent loss of DTH transferring capacity. The oxidation-induced effects following treatment of PETLs with neuraminidase plus galactose oxidase or with periodate could be reversed by subsequent reduction with borohydride of the previously formed aldehyde moieties. Decreased DTH reactions observed after the various treatment procedures were paralleled by reduced immigration of PETLs into sites of antigen deposition, indicating that the reduction/oxidation state of cell surface carbohydrates is crucial for induction of inflammatory processes by T cells. Trapping of PETLs in the liver could not be the sole mechanism since neuraminidase- and periodate-treated PETLs, but not neuraminidase plus galactose oxidase-treated PETLs, accumulated in the liver. It therefore appears that alterations in the reduction/oxidation state of the cell surface can lead to unresponsiveness of T cells to inflammatory signals.

T gamma lymphocytes of peripheral blood and synovial fluid in rheumatoid arthritis: quantitative determination and qualitative analysis

The distribution of T gamma lymphocytes in the peripheral blood of one group of rheumatoid patients and in the synovial fluid in a second group was determined. The results were compared to those found for peripheral blood (PB) lymphocytes of normal subjects and for synovial fluid lymphocytes of osteoarthrosis and meniscitis patients. Besides recording percentage and absolute number, we also used cytofluorographic analysis to determine individual capacity of PB T gamma cells to bind heat-aggregated IgG (agg-IgG). The following results were found: 1) there is no significant difference between the percentage and absolute number of PB T gamma lymphocytes of rheumatoid arthritis (RA) patients and those of controls, 2) individual RA PB T gamma cells had a greater number and/or avidity of Fc receptor for IgG than those cells of controls, and 3) the percentage of RA T gamma lymphocytes in synovial fluid, revealed by IgG-EA ox rosetting, is significantly lower than that found in control patients. The factors that may determine a similar lymphocyte picture in RA are discussed.

Analysis of the peanut agglutinin-binding site as a differentiation marker of normal and malignant human lymphoid cells

The lectin peanut agglutinin (PNA), which interacts specifically with D-galactosyl residues, was studied for its binding to human normal and malignant lymphoid cells at various stages of differentiation. As previously reported, PNA binds to thymocytes; however, it does not interact with the prothymocytes which precede the cortical thymocyte differentiation stage. No mature peripheral cells in any of the lymphoid organs bind PNA. In contrast to the normal T differentiation pathway, the expression of the PNA-binding site does not seem to coincide with that of T cell characteristics in the various malignant lymphoid cells studied. We therefore conclude that more information is needed about the nature of the PNA-binding site before it can be used as a differentiation marker in malignant lymphoid cells.

Isolation and characterization of a major glycoprotein from milk-fat-globule membrane of human breast milk

A major periodate--Schiff-positive component from milk-fat-globule membrane of human breast milk has been purified by selectively extracting the membrane glycoproteins, followed by lectin affinity chromatography and gel filtration on Sephadex G-200 in the presence of protein-dissociating agents. The purified glycoprotein, termed epithelial membrane glycoprotein (EMGP-70), has an estimated mol.wt. of 70 000 and yields a single band under reducing conditions on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The glycoprotein contains 13.5% carbohydrate by weight, with fucose, mannose, galactose, N-acetylglucosamine and sialic acid 17.2, 17.0, 21.1, 7.9 and 36.6% respectively of the carbohydrate moiety. Aspartic and glutamic acid and serine are the major amino acid residues.

Morphological changes in paracortical high endothelial venules to single and repeated application of oxazolone to mouse skin

Morphological changes in paracortical high endothelial venules (HEV) have been studied after single and repeated applications of oxazolone to mouse skin. The primary response was characterized by a rapid and marked vascular dilatation, by marked increase in the cross sectional area of the vessel wall and in the size of the individual endothelial cells, as well as increased accumulation of lymphocytes in HEV walls. These changes regressed (in the more long lasting response). The transitory structural alterations may be related to increase of blood flow, increased flow of cells from the thymus to the stimulated lymph nodes as well as increased transport capacity of endothelial cells based on augmentation of their surface area. These features are closely related to other cellular events such as a prominent blastoid reaction in the paracortex as well as an associated cellular depletion of the thymus.

Gangliosides of calf thymus and of normal and leukemic bovine lymphocytes

The gangliosides of calf thymus and of lymphocytes from blood, lymph nodes, lymph and spleen of normal and leukemic cows were investigated in an attempt to determine whether there exists a relation between the ganglioside composition and the maturity of the lymphocytes. With all normal peripheral lymphocytes studied the largely prevailing (up to 97%) ganglioside component was found to be N-glycoloylneuraminosyllactosylceramide. The ganglioside spectrum of calf thymus was much more complex and included at least six different components. By thin-layer chromatography, methylation analysis and neuraminidase treatment they were identified as N-glycoloylneuraminosyl and N-acetylneuraminosyl lactosylceramides, N-glycoloylneuraminosylneolactotetraosylceramide, di-(N-glycoloylneuraminosyl), di-(N-acetylneuraminosyl) lactosylceramides and N-glycoloylneuraminosyl-N-acetylneuraminosyllactosylceramide. The ganglioside spectra of leukemic peripheral lymphocytes were different from those of normal peripheral lymphocytes and resembled the ganglioside profile of the thymus. The data obtained indicate that, in the normal animal, the development of thymocytes into mature peripheral lymphocytes is accompanied by loss of disialosyl-gangliosides and sialosylneolactotetraosylceramide. It is concluded that both the structure and the composition of the lymphocyte ganglioside become more simple during maturation and ageing of the lymphocyte.

Cell interactions between hematopoietic and stromal cells in the embryonic chick bone marrow

Light microscopic, scanning electron microscopic, and transmission electron microscopic studies of the early developmental stages of chick embryonic bone marrow disclose characteristic associations of the first hematopoietic cells with stromal cells. The first hematopoietic cells, large basophilic cells that we have termed presumptive stem cells, segregate into erythropoietic and granulopoietic regions. Intravascular erythropoietic cells associate with sinusoidal endothelial cells, while granulopoietic cells associate with extravascular reticular cells. Extensive, intimate contacts between erythroid and endothelial cells are maintained, in part, by marginal arrays of microtubules, which promote a flattening of the adherent erythroid cell surface. In addition, cell surface components of opposing cells, visualized by ruthenium red staining, appear to merge and possibly to interact. Granulopoietic cells establish intimate but less extensive associations with reticular cells through cell-surface interactions. Stationary granuloid cells appear to be held in place by small, thin processes emanating from the sheet-like reticular cells. Granuloid cells are capable of moving within the extravascular region, using reticular cell surfaces as a substrate. Intimate associations also occur among granulopoietic cells, the significance of which is unclear. Thus, sinusoidal endothelial cells and reticular cells comprise the critical non-hematopoietic or stromal elements of avian bone marrow, where they have a putative role in segregating presumptive stem cells into erythrocyteic and granulocytic compartments. They serve as an architectual, and possibly regulatory, framework on which hematopoiesis occurs.

Metabolic carbohydrate-labelling of glycolipids from mouse splenocytes. Mitogen-stimulated B and T cells show different labelling patterns

Splenic lymphocytes from CBA/J, AKR/A/J, BALB/c/A, C57/BL/6J, C3H/HeJ and C3H/Tif nu/nu mice and B lymphocyte or T lymphocyte preparations derived from CBA/J mouse spleen were cultivated in the presence of either concanavalin A, phytohemagglutinin, Salmonella minnesota R595 lipopolysaccharide or Proteus mirabilis soluble lipoprotein. The mitogens stimulated the incorporation of [14C]galactose into acid-insoluble cell material with the same specificity for B or T cells as that known for thymidine incorporation. The glycolipids extracted from mitogen-activated, carbohydrate-labelled B or T cells were compared by thin-layer chromatography and characteristic differences between B and T cells were noted in the ganglioside as well as in the neutral glycolipid fractions. In addition, subsets of B or T cells, namely lipopolysaccharide-responsive or lipoprotein-responsive B-cell populations or nylon-purified T cells may be recognized by characteristic neutral glycolipid bands.

Effect of viruses on luminol-dependent chemiluminescence of human neutrophils

The effects of Newcastle disease, herpes simplex, vaccinia, encephalomyocarditis, vesicular stomatitis and reoviruses on in vitro function of neutrophils were studied in Ficoll-Hypaque-separated polymorphonuclear leukocytes (PMN) employing the technique of luminol-dependent chemiluminescence. Newcastle disease, herpes simplex vaccinia, and reoviruses depressed chemiluminescence by 98, 65, 46, and 29%, respectively, while encephalomyocarditis and vesicular stomatitis viruses had no inhibitory effect. None of the viruses affected phagocytosis or PMN viability. These observations suggest significant alteration of neutrophil function by interaction with several viruses in in vitro settings. It is suggested that similar changes in PMN function may occur during in vivo viral infection.