ELAM-1 mediates cell adhesion by recognition of a carbohydrate ligand, sialyl-Lex

Inhibition of selectin-dependent tumor cell adhesion to endothelial cells and platelets by blocking O-glycosylation of these cells

Expression of sialosyl-Le(x) (SLe(x)) and sialosyl-Le(a) (SLe(a)) on tumor cell lines HL60, Colo205, and U937 was greatly suppressed by application of benzyl-alpha-GalNAc for inhibition of O-linked carbohydrate chain extension, which resulted in reduced adhesion of tumor cells to activated endothelial cells or platelets mediated by ELAM-1 (E-selectin) or GMP-140 (P-selectin). Inhibitors or modifiers of N-glycosylation had no effect on expression of SLe(x) or SLe(a) in these tumor cells. These findings suggest the possibility that targeting of O-glycosylation inhibitors or modifiers to tumor cells may effectively suppress metastatic potential.

Recombinant E-selectin-protein mediates tumor cell adhesion via sialyl-Le(a) and sialyl-Le(x)

E-selectin (previously known as ELAM-1) is one of the adhesion molecules expressed on activated endothelium. Here we show that HL-60 cells express sialyl-Le(x), but not Sialyl-Le(a) on their surface, a colon carcinoma cell line COLO 205 express both these epitopes and another colon carcinoma COLO 320 does not express either one of them. HL-60 and COLO 205 cell adhere strongly to E-selectin coated microwells, whereas COLO 320 does not adhere at all to E-selectin. Finally we provide evidence that monoclonal anti-sialyl-Le(x) can abolish part of the adherence of HL-60 cells to recombinant E-selectin. The adherence of COLO 205 cells can be decreased by either monoclonal anti-sialyl-Le(a) or anti-sialyl-Le(x) antibodies. These results indicate that cell-associated sialylated carbohydrate moieties can act as ligands for recombinant E-selectin.

Cell adhesion molecules in neoplastic disease

In a variety of human malignancies, tumorigenesis and the development of metastatic disease are accompanied by changes in the expression of cell adhesion molecules. In carcinomas, normally expressed cell adhesion molecules are lost, or expressed in a functionally altered form, events which may help tumor cells to escape from contact-mediated controls and leave the primary tumor. The development of metastatic potential is, in a number of solid tumors, associated with the expression of new cell adhesion molecules by the tumor cells. These newly expressed cell adhesion molecules appear to mediate tumor cell interaction with leukocytes and endothelium, and may direct dissemination of the tumor cells throughout the body.

Synthesis of a position isomer of ganglioside GD3 having an alpha-Neu5Ac-(2----9)-alpha-Neu5Ac linkage

A position isomer of ganglioside GD3 has been synthesized in which N-acetylneuraminic acid (Neu5Ac) is linked alpha-glycosidically at C-9 of the Neu5Ac residue of the ganglioside GM3, structure. The coupling of 2-(trimethylsilyl)ethyl O-(6-O-benzoyl-beta-D-galactopyranosyl)-(1----4)-2,6-di-O-benzoyl-beta-D -glucopyranoside with methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto -2-nonulopyranosylonate)-(2----9)-(methyl 5-acetamido-4,7,8-tri-O-acetyl-3,5-dideoxy-2-thio-D-glycero-D-galacto-2 -nonulopyranosid)onate, prepared from the corresponding 2-(trimethylsilyl)ethyl glycoside by selective removal of the 2-(trimethylsilyl)ethyl group, 1-O-acetylation, and introduction of the methylthio group with trimethyl(methylthio)silane, using N-iodosuccinimide-trifluoromethanesulfonic acid as a glycosylation catalyst, gave a tetrasaccharide (5). Compound 5 was converted, via O-acetylation, selective removal of the 2-(trimethylsilyl)ethyl group, and subsequent imidate formation, into a protected alpha-Neu5Ac-(2----9)-alpha-Neu5Ac-(2----3')-alpha-lactosyl trichloroacetimidate (8). Glycosylation of (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol with 8 afforded a ceramide precursor which was transformed, via selective reduction of the azido group, coupling with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester groups, into to the little ganglioside.

Vascular adhesion molecules in acute and chronic liver inflammation

Adhesion to and penetration through the sinusoidal vascular endothelium is a mandatory step for leukocyte migration and accumulation at sites of liver inflammation. This leukocyte trafficking is controlled by interactions between adhesion molecules on leukocytes and corresponding ligands on endothelial cells. We have analyzed the in situ distribution of two recently described vascular adhesion molecules (i.e., endothelial leukocyte adhesion molecule-1 and vascular cell adhesion molecule-1) and of the lymphocyte "homing" receptor cluster of differentiation antigen-44 in normal and inflamed liver biopsy specimens. Endothelial leukocyte adhesion molecule-1 and vascular cell adhesion molecule-1 were absent from normal liver tissue, but they were strongly expressed on sinusoidal lining cells in inflammatory liver disease. Endothelial leukocyte adhesion molecule-1 expression predominated diffusely throughout the liver parenchyma in acute hepatitis; in contrast, vascular cell adhesion molecule-1 was mainly expressed in areas of periportal and intralobular inflammation in chronic active and persistent hepatitis. The "homing" receptor cluster of differentiation antigen-44 was weakly expressed on scattered mononuclear cells and on sinusoidal lining cells in normal liver tissue, but it was strongly up-regulated on mononuclear inflammatory cells and sinusoidal lining cells in acute and chronic hepatitis. In addition, reactivity for the cluster of differentiation antigen-44 was found on the membranes of variously sized clusters of hepatocytes in biopsy specimens with acute hepatitis. De novo or up-regulated expression of these adhesion molecules on sinusoidal lining cells in inflamed liver biopsy specimens indicates that these cells actively modulate their phenotype in response to environmental factors, thus playing a key role in the recruitment of leukocytes in acute and chronic liver inflammation.

Sialosylated lewis x expression in CD30-positive anaplastic large-cell lymphomas

The expression of sialosylated Lewis chi (SLEX), a ligand for endothelial leukocyte adhesion molecule 1 in malignant lymphomas, was immunohistochemically examined, using the monoclonal antibody, CSLEX1, which specifically reacts with SLEX. It was expressed in 6 out of 64 non-Hodgkin's lymphomas, which consisted of 1 nasal large-cell lymphoma and 5 of 8 (62%) Ki-1-positive anaplastic large-cell lymphomas (ALCL). One nasal lymphoma positive for SLEX co-expressed a T cell marker, cluster of differentiation (CD) 5, and natural killer (NK) cell markers such as CD56 and CD16, indicating that SLEX+ nasal lymphoma cells are possibly malignant counterparts of SLEX+ NK cells. SLEX did not react with 30 B cell lymphomas or most Hodgkin's disease lymphomas, though it did with one lymphocyte predominance type. Although SLEX+ ALCL exhibit T cell markers in some cases, some ALCL expressing SLEX may represent histiocytic differentiation of the neoplastic cells. The lymphoma cells of ALCL were preferentially positive for SLEX, in contrast to Hodgkin's disease cells, and thus CSLEX1 in conjunction with CD30 and CD15 should be of use for analyzing and making differential diagnoses of routine paraffin-embedded sections of ALCL.

Alteration in keratinocyte ganglioside content in basal cell carcinomas

We examined the ganglioside content of normal human keratinocytes and basal cell carcinomas (BCC). The total ganglioside content of the epidermis was 0.098 +/- 0.01 microgram lipid-bound sialic acid/mg dry weight. GM3 was the predominant ganglioside of epidermis. GM2 and GD3 were also found in significant amounts. Polysialylated gangliosides were identified in only small amounts. In contrast to all other body locations, breast epidermis showed large amounts of GM1. The total ganglioside content of nodular and sclerosing facial BCC was approximately 3.5 times that of normal facial epidermis. This marked elevation of total ganglioside was not affected by dermal ganglioside contamination, because the total ganglioside content of the dermis was similar to that of the epidermis. The relative percentage of GM2 was significantly decreased, whereas the relative percentage of GM3 was slightly decreased in BCC. 9-O-acetyl-GD3 was present in the BCC, but not in normal epidermis or dermis. 9-O-acetyl-GD3 may be a surface marker for BCC. Furthermore, the alterations in amount and composition of individual gangliosides on neoplastic membranes may lead to novel therapeutic interventions.

Cell-cell contact mechanisms

Exciting new findings link characteristic properties of the inflammatory process previously not linked functionally. For example, it is now clear that oxygen radicals and leukocyte adhesion are intimately related in a carefully transduced and orchestrated series of events that culminates in release of granule contents, but not before the leukocyte has safely transversed the vessel wall. In addition to defining separate heterocellular contacts and homocellular aggregation we must now consider equilibrium events that allow associations among cell-cell partnerships involving different cell types.

Isolation of two novel sialyl-Lewis X-active oligosaccharides by high-performance liquid affinity chromatography using monoclonal antibody Onc-M26

A monoclonal antibody, Onc-M26, that recognizes a cancer-associated antigen expressed by most human adenocarcinomas of the breast was shown previously to recognize a carbohydrate epitope carried on a hexaglycosyl ganglioside carrying the sialyl-Lewis X (SLex) antigen (P.S. Linsley et al., 1988, Cancer Res. 48, 2138-2148). Evidence that the antibody binds even more avidly to minor gangliosides containing more complex carbohydrate chains prompted us to search for a higher affinity epitope among sialylated oligosaccharides from pooled human milk. Affinity chromatography of a partially purified fraction of monosialylated milk oligosaccharides on a column containing monoclonal antibody Onc-M26 bound to a macroporous silica matrix gave a peak with a retention volume significantly greater than that of a standard SLex-active hexasaccharide. The retained material consisted of two nonasaccharides, each containing the SLex tetrasaccharide sequence, Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3) GlcNAc, linked beta 1-6 to a 3,6-disubstituted galactosyl residue.

Complex carbohydrates in drug development

Recent advances in carbohydrate chemistry and biochemistry afford the opportunity to develop bioactive complex carbohydrates, per se , as drugs or as lead compounds in drug development. Complex carbohydrates are unique among biopolymers in their inherent potential to generate diverse molecular structures. While proteins vary only in the linear sequence of their monomer constituents, individual monosaccharides can combine at any of several sites on each carbohydrate ring, in linear or branched arrays, and with varied stereochemistry at each linkage bond. This chapter addresses some salient features of mammalian glycoconjugate structure and biosynthesis, and presents examples of the biological activities of complex carbohydrates. The chapter presents selected examples that will provide an accurate introduction to their pharmacological potential. In addition to their independent functions, oligosaccharides can modify the activities of proteins to which they are covalently attached. Many glycoprotein enzymes and hormones require glycosylation for expression and function. The chapter discusses the ancillary role of carbohydrates that is of great importance to the use of engineered glycoproteins as pharmaceuticals.

Leukocyte traffic to sites of inflammation

The adhesion of circulating leukocytes to the vascular endothelium is essential for effective host inflammatory and immune responses. Adhesion proteins expressed by both the leukocyte and endothelial cell have been well characterized, and studies of these molecules have shown that both cell types are actively involved in regulating these binding events. Most leukocyte (leukocyte integrins) and endothelial cell (vascular selectins, ICAM-1, and VCAM) adhesion proteins increase in expression and function in response to mediators released by inflamed tissues. In contrast, the expression and function of one type of leukocyte molecule, L-selectin (previously called LECAM-1, LAM-1, gp90MEL-14), is "down-regulated" by inflammatory signals. The purpose of this review is to summarize in vitro and in vivo regulatory and functional studies of some of the molecular mechanisms which regulate leukocyte-endothelial cell adhesion, with particular emphasis on L-selectin, and to present a hypothetical model of how these molecules may be orchestrated in vivo resulting in the control of host inflammatory responses.

Adhesive interactions in angiogenesis and metastasis

A variety of adhesive interactions must take place between the tumor cell and the host vasculature in order to potentiate both tumor expansion and metastatic tumor spread. The study of tumor cell and blood vessel adhesive interactions becomes essential for our understanding of the malignant process, especially with regard to organ-specific tumor metastasis. In this article we will review recent progress made in our understanding of the nature of (i) receptor mediated adhesion of endothelial cells to extracellular matrix components and (ii) adhesion of tumor cells to endothelial adhesion molecules and to components of the subendothelial basement membrane.

Association of glycosphingolipids with intermediate filaments of mesenchymal, epithelial, glial, and muscle cells

We reported recently that two glycosphingolipids (GSLs), globoside (Gb4) and ganglioside GM3, colocalized with vimentin intermediate filaments of human umbilical vein endothelial cells. To determine whether this association is unique to endothelial cells or to vimentin, we analyzed a variety of cell types. Double-label immunofluorescent staining of fixed, permeabilized cells, with and without colcemid treatment, was performed with antibodies against glycolipids and intermediate filaments. Globoside colocalized with vimentin in human and mouse fibroblasts, with desmin in smooth muscle cells, with keratin in keratinocytes and hepatoma cells, and with glial fibrillary acidic protein (GFAP) in glial cells. Globoside colocalization was detected only with vimentin in MDCK and HeLa cells, which contain separate vimentin and keratin networks. GM3 ganglioside also colocalized with vimentin in human fibroblasts. Association of other GSLs with intermediate filaments was not detected by immunofluorescence, but all cell GSLs were detected in cytoskeletal fractions of metabolically labelled endothelial cells. These observations indicate that globoside colocalizes with vimentin, desmin, kertain and GFAP, with a preference for vimentin in cells that contain both vimentin and keratin networks. The nature of the association is not yet known. Globoside and GM3 may be present in vesicles associated with intermediate filaments (IF), or bound directly to IF or IF associated proteins. The prevalence of this association suggests that colocalization of globoside with the intermediate filament network has functional significance. We are investigating the possibility that intermediate filaments participate in the intracellular transport and sorting of glycosphingolipids.

Selectin GMP-140 (CD62; PADGEM) binds to sialosyl-Le(a) and sialosyl-Le(x), and sulfated glycans modulate this binding

GMP-140 (CD62; PADGEM) is a member of the selectin family expressed highly at the surface of platelets and endothelial cells by agonists such as thrombin or phorbol esters. Previous studies indicate that the lectin domain of GMP-140 recognizes sialosyl-Le(x) (SLex) and to a lesser extent Le(x) (Polley MJ, et al., Proc Natl Acad Sci USA 88:6224, 1991). We now report that GMP-140 binds to sialosyl Lea (SLea) and to SLex, and that degree of binding to SLea is greater than that to SLex under our experimental conditions. Binding of activated platelets to SLea or SLex was inhibited to various degrees in the presence of sulfated glycans, suggesting that sulfated glycans induce conformational change in the lectin domain of GMP-140 and modulates its binding affinity to SLea and SLex.

Expression of a carbohydrate signal, sialyl dimeric Le(x) antigen, is associated with metastatic potential of transitional cell carcinoma of the human urinary bladder

Sialyl dimeric Le(x) antigen was expressed in significant portion of transitional cell carcinoma of the human urinary bladder, but not in the normal uroepithelial tissue. Primary tumors with weak or no expression of the antigen scarcely metastasized to lymph nodes, whereas tumors with high levels of antigen expression metastasized frequently. Metastatic lymph nodes expressed the antigen in most cases. Sialyl dimeric Le(x) antigen was mainly located on 60 and 42 KDa glycoproteins. Since a group of cell adhesion molecules, called LECCAMs, recognize a portion of the antigen, the above results strongly suggest that a LECCAM on the surface of host cells recognizes the carbohydrate structure on the glycoprotein, leading to promotion of metastasis.

Analysis of sialic acid-containing mucin oligosaccharides from porcine small intestine by high-temperature gas chromatography-mass spectrometry of their dimethylamides

Acetylation of sialic acid-containing oligosaccharides lactonises the sialic acid residue quantitatively for all oligosaccharides studied except for 6'-sialyl-lactose. The modified, unsulphated, sialylated and sulphated oligosaccharides can then be fractionated by anion-exchange chromatography. Ammonolysis of the lactones followed by methylation yielded the dimethylamides, which are amenable to g.l.c.-m.s. and give intense and informative mass spectra. This approach has been used to characterise the sialic acid-containing O-linked oligosaccharides obtained from the mucin glycopeptides of the small intestine of the pig. At least 28 structures were found, having NeuAc or NeuGc 6-linked to the HexNAc attached to the peptide core or to a Hex 3-linked to HexNAc. Four different disialylated oligosaccharides were found having NeuAc or NeuGc on the Hex residue 3-linked to HexNAc and 6-linked to HexNAc.

Neutral glycosphingolipid expression in B-cell neoplasms

The expression of neutral glycosphingolipids (GSL) in 37 B-cell neoplasms [7 acute lymphocytic leukemia (ALL), 5 Burkitt's lymphoma (BL), 7 chronic lymphocytic leukemia (CLL), 5 diffuse, poorly differentiated lymphoma (DPDL), 6 diffuse histiocytic lymphoma (DHL), 3 hairy-cell leukemia (HCL), and 4 multiple myeloma (MM)] was examined. Patterns of expression of simple (GlcCer, LacCer) and globo-series GSL (Gb3, Gb4) were found for each tumor type. In addition, pre-B ALL expressed the neo-lacto series GSL, paragloboside, which was not significantly seen at later stages of maturation. As a group, leukemias expressed about 10 times higher ratios of simple GSL to Globo-series GSL as compared to lymphomas, regardless of stage of differentiation. Significant amounts of GSL of other series were not found except in one CLL which contained asialo-GM2. GSL phenotype in these cells was not grossly affected by cell genotype since pre-B ALL containing Philadelphia chromosome t(9q;22q) translocations were similar to other ALL; and DHL with t(8q;14q) translocations had GSL patterns similar to other DHL samples and dissimilar to GSL patterns found in Burkitt's lymphomas with t(8q;14q). Differences in GSL expression among the different types of B-cell neoplasm suggested that GSL patterns form a phenotypic map that may complement the traditional glycoprotein immunophenotypic map and contribute to our understanding of the biology of these diseases and B-cell differentiation.

Activation of two new alpha(1,3)fucosyltransferase activities in Chinese hamster ovary cells by 5-azacytidine

Several mammalian alpha(1,3)fucosyltransferases (alpha[1,3]Fuc-T) that synthesize carbohydrates containing alpha(1,3)fucosylated lactosamine units have been identified. Although Chinese hamster ovary (CHO) cells do not express alpha(1,3)Fuc-T activity, the rare mutants LEC11 and LEC12, isolated after mutagenesis or DNA transfection, each express an alpha(1,3)Fuc-T that may be distinguished by several criteria. Two new CHO mutants possessing alpha(1,3)Fuc-T activity (LEC29 and LEC30) have now been isolated after treatment of a CHO cell population with 5-azacytidine (5-AzaC), ethylnitrosourea (ENU), or 5-AzaC followed by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Like LEC12, both mutants possess an N-ethylmaleimide-resistant alpha(1,3)Fuc-T activity that can utilize a variety of acceptors and both express the Lewis X (Lex) determinant (Gal beta[1,4](Fuc alpha[1,3])GlcNAc beta 1)) but not the sialyl alpha(2,3)Lex determinant on cell-surface carbohydrates. However, LEC29 and LEC30 may be distinguished from LEC11 and LEC12, as well as from each other, on the basis of their unique patterns of lectin resistance and their abilities to bind the VIM-2 monoclonal antibody that recognizes carbohydrates terminating in NeuNAc alpha(2,3)Gal beta(1,4)GlcNAc beta(1,3)Gal beta(1,4)(Fuc alpha[1,3])GlcNAc beta and also by the different in vitro substrate specificities and kinetic properties of their respective alpha(1,3)Fuc-T activities. The combined data provide good evidence that the LEC29 and LEC30 alpha(1,3)Fuc-Ts are novel transferases encoded by distinct gene products.

Direct interaction with primed CD4+ CD45R0+ memory T lymphocytes induces expression of endothelial leukocyte adhesion molecule-1 and vascular cell adhesion molecule-1 on the surface of vascular endothelial cells

The process of recruitment of leukocytes at sites of inflammation involves direct cell-to-cell interactions between leukocytes and vascular endothelial cells (EC) mediated by various adhesion receptors on leukocytes and their inducible endothelial ligands. In this study we have examined the induction on EC of endothelial leukocyte adhesion molecule-1 (ELAM-1), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) upon their interaction with subpopulations of human T cells. When co-cultured with EC both resting CD4+ T and CD8+ T cells caused a modest increase in the expression of endothelial ICAM-1. Moreover, resting CD4+ but not CD8+ T cells induced expression of ELAM-1 and VCAM-1 on a small fraction of unstimulated EC. Prior activation with phorbol 12-myristate 13-acetate (PMA) significantly increased the ability of T cells to up-regulate endothelial ICAM-1 and also induced the expression of both ELAM-1 and VCAM-1. PMA-primed CD4+ T cells induced both VCAM-1 and ELAM-1 on EC more efficiently than CD8+ T cells. Furthermore, the ability to induce the expression of ELAM-1 and VCAM-1 was confined to the CD4+ CD45R0+ memory/primed subpopulation of T cells. This induction of various endothelial adhesion ligands could also be mediated by antigen-primed CD4+ T cell lines. The CD4+ T cell-mediated induction of adhesion ligands required direct intercellular contact with EC because neither cultures of EC and PMA-primed CD4+ T cells separated by a microporous membrane insert nor the conditioned medium of PMA-primed T cells induced expression of ELAM-1 and VCAM-1 on EC. Cyclosporin A significantly inhibited the activation of T cells with PMA but had no effect on the ability of PMA-primed T cells to up-regulate endothelial CAM. Thus, CD4+CD45R0+ T cells via as yet unknown mechanism can significantly enhance the expression of each of the three endothelial adhesion ligands and, thereby, may facilitate the process of recruitment of additional leukocytes to exacerbate inflammation.

Multiple roles of Leu-8/MEL-14 in leukocyte adhesion and function

Leu-8 and its murine homologue MEL-14 are members of a new family of adhesion molecules encoded on chromosome-1 that share common structural features, including lectin-like domains and tandem repeats homologous to complement binding proteins. The expression of Leu-8 is rapidly down-regulated during cell activation, both at the transcriptional level, and by a rapid post-translational event at the cell membrane, probably involving direct cleavage of the molecule from the cell surface. Lymphocytes that express Leu-8/MEL-14 bind selectively to HEVs in peripheral lymph nodes, and MEL-14 on neutrophils is thought to be important in the initial localization of neutrophils to sites of inflammation. In addition to its role in leukocyte adhesion, there is evidence that the Leu-8 molecule plays a role in cell function. Anti-Leu-8 monoclonal antibody increases suppressor activity of CD4+, Leu-8+ T cells for immunoglobulin synthesis, and anti-Leu-8 directly inhibits differentiation of Leu-8+ B cells. Together these findings indicate that the Leu-8 molecule in common with other cellular adhesion molecules is important not only in cellular adhesion, but also in modification of cell function.

Mobilization of sialidase from intracellular stores to the surface of human neutrophils and its role in stimulated adhesion responses of these cells

Desialation of cell surfaces has been associated with the initiation or modification of diverse cellular functions. In these studies we have examined the subcellular distribution of sialidase (SE) in human neutrophils as well as the mobilization of this enzyme following neutrophil activation. Separation of subcellular fractions by density gradient centrifugation showed that SE is present not only in neutrophil primary and secondary granule populations, like lysozyme, but also in plasma membrane fractions. Neutrophil activation was associated with a redistribution of SE from secondary granule-enriched fractions to the plasma membrane. Furthermore, SE activity detected on the surface of intact neutrophils with a fluorescent SE substrate increased rapidly after activation with kinetics that matched both the loss of total cell-associated sialic acid and release of free sialic acid from the cells. These activation-dependent events were in each case blocked by incubation of neutrophils with the SE inhibitor, 2-deoxy-N-acetyl-neuraminic acid. Aggregation responses of neutrophils as well as adhesion responses to nylon and plastic surfaces were also inhibited by 2-deoxyNANA. Our findings indicate that the activation-dependent desialation of the neutrophil surface is associated with mobilization of an endogenous SE to the plasma membrane and has a role in stimulated adhesion responses of these cells.

The cutaneous lymphocyte antigen is a skin lymphocyte homing receptor for the vascular lectin endothelial cell-leukocyte adhesion molecule 1

A skin-associated population of memory T lymphocytes, defined by expression of the cutaneous lymphocyte antigen (CLA), binds selectively and avidly to the vascular lectin endothelial cell-leukocyte adhesion molecule 1 (ELAM-1), an interaction that may be involved in targeting of CLA+ T cells to cutaneous sites of chronic inflammation. Here we present evidence that CLA itself is the (or a) lymphocyte homing receptor for ELAM-1. Antigen isolated with anti-CLA monoclonal antibody HECA-452 from human tonsillar lysates avidly binds ELAM-1 transfected mouse cells. Anti-CLA antibody blocks T lymphocyte binding to ELAM-1 transfectants. HECA-452 and ELAM-1 binding to lymphocytes or to isolated tonsillar HECA-452 antigen is abrogated by neuraminidase treatment implying a prominent role for sialic acid in CLA structure and function. The dominant form of CLA on T cells is immunologically distinct from the major neutrophil ELAM-1 ligand, the sialyl Lewis x (sLex) antigen (NeuAc alpha 2-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc), which is absent, weakly expressed, or masked on T cells. However, neuraminidase treatment of CLA+ T cells, but not of CLA- T cells, reveals Lewis x (CD15) structures. In combination with the known requirement for terminal NeuAc alpha 2-3Gal and fucose residues attached to N-acetylglucosamine for ELAM-1 and HECA-452 binding, this finding suggests that CLA may comprise an additionally sialylated or otherwise modified form of sLex. The identification of a lymphocyte homing receptor for skin may permit novel approaches to the diagnosis and therapy of cutaneous and inflammatory disorders.

Structural requirements for the carbohydrate ligand of E-selectin

The acute inflammatory response requires that circulating leukocytes adhere to, and then migrate through, the vascular wall at the site of injury or infection. Several receptors have been implicated in this adhesion and migration process, including the selectins, a family of carbohydrate-binding proteins. The ligand for one of these proteins, E-selectin (LECAM-2, ELAM-1) has been described by several groups to contain a polylactosamine structure bearing a terminal sialic acid residue and at least one fucose residue. We report here a more detailed investigation into the minimum structural requirements for carbohydrate recognition by E-selectin. Using both direct binding and inhibition studies we demonstrate that the sialyl Lewisx tetrasaccharides Sia(alpha 2-3)Gal(beta 1-4)[Fuc(alpha 1-3)]GlcNAc, and Sia(alpha 2-3)Gal(beta 1-4)[Fuc(alpha 1-3)]Glc are the smallest oligosaccharides recognized by the lectin. In addition, an oligosaccharide containing the sialyl Lewisa epitope is also recognized, but less avidly. We propose a structural model of functional groups necessary for recognition by E-selectin, based on these data and additional experiments on modifications of sialic acid and the reducing terminal saccharide.

Vascular cell adhesion molecule-1 and eosinophil adhesion to cultured human umbilical vein endothelial cells in vitro

Cultured human umbilical vein endothelial cell (EC) monolayers stimulated with 10 ng/ml tumor necrosis factor demonstrate a time-dependent increase in the expression of the vascular cell adhesion molecule-1 (VCAM-1) with maintained maximal expression at 24 h following EC activation. A monoclonal antibody (mAb) directed against VCAM-1 (1G11) significantly inhibited the adhesion of eosinophils, but not neutrophils, to EC, which had been activated by tumor necrosis factor-alpha for 24 h, but only when eosinophils had been pretreated with an mAb directed against the common beta chain of the CD11/CD18 complex. In the absence of pretreatment with anti-CD18, mAb 1G11 had no significant effect on eosinophil adhesion. These results suggest that eosinophils bind to VCAM-1. However, the functional capacity in this model of the eosinophil receptor for VCAM-1 is likely to be minor compared with the activity of the CD11/CD18 leukocyte adhesion molecules.

CD62/P-selectin recognition of myeloid and tumor cell sulfatides

CD62, also called PADGEM protein, GMP-140, or P-selectin, is a granule membrane protein of endothelial cells and platelets that is mobilized to the plasma membrane following exposure to mediators such as thrombin, histamine, complement components, or peroxides. Data presented to date suggest that one ligand of CD62 includes CD15 (Lewis x determinant) and sialic acid. We show here that sulfatides, heterogeneous 3-sulfated galactosyl ceramides, are an apparently unrelated ligand of CD62. Sulfatides are expressed on the plasma membrane of, and are excreted by, granulocytes, and constitute the principal ligand for CD62 on the plasma membrane of some tumor cells. CD62 binds to sulfatides adsorbed to plastic as avidly as it binds to myeloid or tumor cells. We find that granulocytes excrete sulfatides at a rate predicted to allow them to be rapidly released from CD62 once they have exited the bloodstream.

The selectin GMP-140 binds to sialylated, fucosylated lactosaminoglycans on both myeloid and nonmyeloid cells

Granule membrane protein-140 (GMP-140) is an inducible receptor for myeloid leukocytes on activated platelets and endothelium. Like other selectins, GMP-140 recognizes specific oligosaccharide ligands. However, prior data on the nature of these ligands are contradictory. We investigated the structural features required for ligand interaction with GMP-140 using purified GMP-140, cells naturally expressing specific oligosaccharides, and cells expressing cloned glycosyltransferases. Like the related selectin endothelial leukocyte adhesion molecule-1 (ELAM-1), GMP-140 recognizes alpha(2-3)sialylated, alpha(1-3)fucosylated lactosaminoglycans on both myeloid and nonmyeloid cells, including the sequence Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNac beta-R (sialyl Lewis x). Recognition requires sialic acid, because cells expressing large amounts of Lewis x, but not sialyl Lewis x, do not interact with GMP-140. Although sialyl Lewis x is expressed by both myeloid HL-60 cells and CHO cells transfected with an alpha 1-3/4 fucosyltransferase, GMP-140 binds with significantly higher affinity to HL-60 cells. Thus, the sialyl Lewis x tetrasaccharide may require additional structural modifications or specific presentations in order for leukocytes in flowing blood to interact rapidly and with high affinity to GMP-140 on activated platelets or endothelium.

Possible functions of tumor-associated carbohydrate antigens

Expression of some tumor-associated carbohydrate antigens may define the stage, rate and phenotype of tumor progression and may have prognostic value. Some of these antigens are now recognized as adhesion molecules that define the site of metastasis. Monoclonal antibodies to tumor-associated carbohydrate antigens, or the antigens themselves, may serve not only as classic immunological reagents but also as anti-adhesion reagents for the prevention of tumor progression.

The complement binding-like domains of the murine homing receptor facilitate lectin activity

The leukocyte homing receptor (HR), the endothelial leukocyte adhesion molecule, and gmp140/platelet activation-dependent granule membrane protein are members of a family of adhesion molecules, termed the lectin cell adhesion molecules (LEC-CAMS) which are unified by a multi-domain structure containing a lectin motif, an epidermal growth factor-like (egf) motif, and variable numbers of a complement binding-like (CB) motif. Previous data have indicated a predominant role for the lectin motif in cell adhesion directed by the LEC-CAMS, although the egf-like domain of the HR may also play a potential role in cell binding. While the role(s) of the CB domains in the LEC-CAMS is currently not understood, they have been hypothesized to act as rigid spacers or stalks for lectin and perhaps, egf domain presentation. In this paper, we analyze the functional characteristics of murine HR-IgG chimeras containing the lectin, lectin plus egf, and lectin plus egf plus CB domains. The Mel 14 mAb, an adhesion blocking antibody which recognizes a conformational determinant in the N-terminus of the HR lectin domain, shows a significantly decreased affinity for a HR construct which lacks the CB motifs, consistent with the possibility that the CB domains are involved with lectin domain structure. In agreement with this conjecture, HR mutants lacking the CB domains show a profound decrease in lectin-specific interaction with the carbohydrate polyphosphomannan ester, suggesting that the changes in Mel 14 affinity for the lectin domain are reflected in lectin functionality. Various assays investigating the interactions between the HR deletion mutants and the peripheral lymph node high endothelium, including cell blocking, immunohistochemical staining, and radioactively labeled ligand binding, all showed that removal of the CB domains results in a lack of HR adhesive function. These results imply that the CB domains of the HR, and, by analogy, the other members of the LEC-CAM family, may play important structural roles involving induction of lectin domain conformation and resultant functionality.

Role of endothelial-leukocyte adhesion molecule 1 (ELAM-1) in neutrophil-mediated lung injury in rats

Two murine monoclonal antibodies (CL-3 and CL-37, both F(ab')2) to human endothelial-leukocyte adhesion molecule-1 (ELAM-1) were found to react immunohistochemically with rat pulmonary artery endothelial cells that had been pretreated with tumor necrosis factor (TNF alpha). CL-3, but not CL-37, blocked in vitro adherence of neutrophils to TNF alpha-treated endothelial cells and the killing of TNF alpha-treated rat endothelial cells by phorbol ester activated neutrophils. In rats treated systemically with CL-3, there was a 70% reduction in accumulation of neutrophils in glycogen-induced peritoneal exudates. Treatment of animals with CL-37 anti-ELAM-1 did not reduce neutrophil accumulation under the same conditions. When IgG immune complex deposition was induced in dermis and in lungs of rats, treatment with CL-3 anti-ELAM-1 markedly reduced vascular injury as measured by changes in vascular permeability (leakage of 125I-albumin) and hemorrhage (extravasation of 51Cr-red blood cells). The protective effects of CL-3 anti-ELAM-1 were related to greatly diminished recruitment of neutrophils (as assessed morphologically, by tissue extraction of myeloperoxidase, and by retrieval, via bronchoalveolar lavage, of neutrophils from lung). CL-37 had no protective effects in vivo after deposition of immune complexes in lung. Using either CL-3 or CL-37 anti-ELAM-1, immunohistochemical analysis of lungs undergoing IgG immune complex-induced injury revealed a striking upregulation of ELAM-1 in the lung vasculature (venules and interstitial capillaries), with a peak intensity developing between 3 and 4 h after deposition of immune complexes in lung. Vascular beds of spleen, liver, and kidney failed to show upregulation of ELAM-1 under these same conditions. The immunohistochemical reactivity of rat lung was abolished if the anti-ELAM-1 preparation was first absorbed with monolayers of human umbilical vein endothelial cells that had been pretreated with TNF alpha. Untreated human endothelial cells failed to cause loss of lung reactivity of the anti-ELAM-1 preparation. These data indicate that ELAM-1 is upregulated in the pulmonary vasculature of rats during deposition of immune complexes and that ELAM-1 appears to play an obligate role in the recruitment of neutrophils.

The B lymphocyte adhesion molecule CD22 interacts with leukocyte common antigen CD45RO on T cells and alpha 2-6 sialyltransferase, CD75, on B cells

Functional maturation of B lymphocytes correlates with expression of the B lineage-specific cell surface glycoprotein CD22. Two CD22 polypeptides have been characterized and suggested to play a role in B cell-B cell interaction as well as in B cell adhesion to monocytes. In this work we provide evidence that CD22 is directly involved in the cognate interaction between B and T cells. One of the two CD22 polypeptides, CD22 beta, interacts with a specific ligand on a subpopulation of CD4+ T cells. Our results suggest that the T cell ligand of CD22 is CD45RO, an isoform of the leukocyte common antigen class of phosphotyrosine phosphatases associated with the helper T cell phenotype. We further demonstrate that CD22 recognizes a second ligand, CD75, expressed predominantly on activated B cells and shown to be a cell surface alpha 2-6 sialyltransferase.

Adhesion of human cancer cells to vascular endothelium mediated by a carbohydrate antigen, sialyl Lewis A

Recently the lectin-like domain on ELAM-1 (endothelial leukocyte adhesion molecule-1) was shown to recognize a carbohydrate antigen, sialyl Lewis x. In this paper we demonstrate, by a series of inhibition experiments utilizing specific monoclonal antibodies and pure glycolipid preparations, that the sialyl Lewis a antigen serves as a specific ligand for ELAM-1 as well as sialyl Lewis x and plays a significant role in the ELAM-1-mediated binding of human cancer cells to activated endothelial cells.

Lewis blood group antigens (a and b) in human breast tissues. Loss of Lewis-b in breast cancer cells and correlation with tumor grade

The Lewis blood group antigens (Lewis-a [Lea] and Lewis-b [Leb]) and their precursors are present on various normal human epithelial cell surfaces. The authors examined 35 benign and malignant human breast lesions using mouse monoclonal antibodies to synthetic Lea and Leb carbohydrate antigens. Normal breast lobular and ductal epithelium and benign breast lesions showed Leb staining but only occasional Lea staining. In invasive ductal carcinomas of breast, of all grades, a loss of Leb antigen staining was found in 80% of the breast cancer cases. This reduced Leb antigen expression increased with the grade of malignancy. Therefore, the loss of Leb blood group antigens on breast cancer cell surfaces may suggest altered fucosylation patterns in malignant cells and reflect the degree of malignancy and/or invasiveness.

The neutrophil selectin LECAM-1 presents carbohydrate ligands to the vascular selectins ELAM-1 and GMP-140

LECAM-1 (leukocyte-endothelial cell adhesion molecule 1), the lymphocyte lectin ("selectin") homing receptor for peripheral lymph nodes (PLNs), participates in the earliest interactions of polymorphonuclear neutrophilic leukocytes (PMNs) with inflamed venules. Here, we present evidence that LECAM-1 mediates this function through a novel mechanism--presentation of oligosaccharide ligands to the inducible vascular selectins endothelial-leukocyte adhesion molecule (ELAM-1) and granule membrane protein 140 (GMP-140). PMN, but not lymphocyte, LECAM-1 is modified with the vascular selectin ligand sialyl Lewis x (sLex) and specifically binds ELAM-1-transfected cells. Although only a small fraction of total cell surface sLex, LECAM-1-associated sLex appears to play a prominent role in PMN interactions with cell-associated ELAM-1 and GMP-140, as anti-LECAM-1 monoclonal antibodies or selective removal of cell surface LECAM-1 inhibits PMN binding to vascular selectin transfectants by up to 70%. The enhanced function of LECAM-1-associated sLex may reflect the striking concentration, shown here, of LECAM-1 on PMN surface microvilli, the site of initial cellular contact.

Leukocyte adhesion in host defense and tissue injury

During their life span, leukocytes adhere transiently to one another, to other cell types, such as vascular endothelial cells, and to extracellular matrix proteins. This adhesiveness is mediated by families of specific cell surface adhesion molecules, namely, integrins, immunoglobulin superfamily molecules, and selectins. Adhesion is required for leukocyte-mediated cytotoxicity, phagocytosis, chemotaxis, and induction of lymphocyte proliferation and maturation. It also participates in recirculation and homing of lymphocytes into lymphoid organs and in leukocyte migration from the vascular compartment to extravascular tissues. Adhesion underlies the beneficial or detrimental role of leukocytes in immune and inflammatory responses. In animals, blocking monoclonal antibodies to adhesion molecules dramatically reduce vascular and tissue injury in several organs following ischemia-reperfusion, and delay renal allograft rejection. Moreover, expression of particular adhesion molecules is induced or increased in cells which are targets for allergic or autoimmune reactions and in inflamed tissues. On the other hand, a congenital deficiency of the CD11/CD18 integrins (Leu-CAMs) leads to recurrent, and sometimes fatal, bacterial infections, and lack of particular cell-adhesion molecules on Burkitt's lymphoma cells may enable these cells to escape immunosurveillance.