Quantitative agglutination of specific populations of sea urchin embryo cells with concanavalin A

It has been demonstrated that specific changes in carbohydrate-containing cell surface lectin receptor sites occur with differentiation and maturation of sea urchin embryo cells. In this study, evidence is presented, using a quantitative electronic particle counter assay to measure agglutination, which indicates that concanavalin A (Con A) mediated agglutination of dissociated 32/64 cell sea urchin embryos differs dramatically with respect to specific cell populations. The migratory cell type, the micromere, is significantly more agglutinable with Con A than the other cell types and colchicine treatment markedly increases sea urchin embryo cell agglutinability. The results indicate that like many malignant cells which display extensive migratory behavior, specific migratory populations of embryonic cells are agglutinable with Con A. The results are discussed with respect to the possible nature of lectin receptor sites on specific populations of embryonic cells and the possible role of colchicine-sensitive structures in controlling the display patterns of these sites.     

Platelet endothelial cell adhesion molecule, PECAM-1, modulates cell migration.

Cell migration is an important process in such phenomena as growth, development, and wound healing. The control of cell migration is orchestrated in part by cell surface adhesion molecules. These molecules fall into two major categories: those that bind to extracellular matrix and those that bind to adjacent cells. Here, we report on the role of a cell-cell adhesion molecule, platelet-endothelial cell adhesion molecule-1, (PECAM-1), a member of the lg superfamily, in the modulation of cell migration and cell-cell adhesion. PECAM-1 is a 120-130 kDa integral membrane protein that resides on endothelial cells and localizes at sites of cell-cell contact. Since endothelial cells express PECAM-1 constitutively, we studied the effects of PECAM-1 on cell-cell adhesion and migration in a null-cell population. Specifically, we transfected NIH/3T3 cells with the full length PECAM-1 molecule (two independent clones). Transfected cells containing only the neomycin resistance gene, cells expressing a construct coding for the extracellular domain of the molecule, and cells expressing the neu oncogene were used as controls. The PECAM-1 transfectants appeared smaller and more polygonal and tended to grow in clusters. Indirect immunofluorescence of PECAM-1 transfectants showed peripheral staining at sites of cell-cell contact, while the extracellular domain transfectants and the control cells did not. In two quantitative migration assays, the full-length PECAM-1 transfectants migrated more slowly than control cells. Thus, PECAM-1 transfected into a null cell appears to localize to sites of cell-cell contact, promote cell-cell adhesion, and diminish the rate of migration. These findings suggest a role for this cell-cell adhesion molecule in the process of endothelial cell migration.     

Polyadenylation of nascent RNA during the embryogenesis of Ilyanassa obsoleta.

It has been demonstrated that specific changes in carbohydrate-containing cell surface lectin receptor sites occur with differentiation and maturation of sea urchin embryo cells. In this study, evidence is presented, using a quantitative electronic particle counter assay to measure agglutination, which indicates that concanavalin A (Con A) mediated agglutination of dissociated $\text{32}\text{64}$ cell sea urchin embryos differs dramatically with respect to specific cell populations. The migratory cell type, the micromere, is significantly more agglutinable with Con A than the other cell types and colchicine treatment markedly increases sea urchin embryo cell agglutinability. The results indicate that like many malignant cells which display extensive migratory behavior, specific migratory populations of embryonic cells are agglutinable with Con A. The results are discussed with respect to the possible nature of lectin receptor sites on specific populations of embryonic cells and the possible role of colchicine-sensitive structures in controlling the display patterns of these sites.     

Expression and function of cell adhesion molecules during neural crest migration

Neural crest cells are highly migratory cells that give rise to many derivatives including peripheral ganglia, craniofacial structures and melanocytes. Neural crest cells migrate along defined pathways to their target sites, interacting with each other and their environment as they migrate. Cell adhesion molecules are critical during this process. In this review we discuss the expression and function of cell adhesion molecules during the process of neural crest migration, in particular cadherins, integrins, members of the immunoglobulin superfamily of cell adhesion molecules, and the proteolytic enzymes that cleave these cell adhesion molecules. The expression and function of these cell adhesion molecules and proteases are compared across neural crest emigrating from different axial levels, and across different species of vertebrates.     

Receptor mobility and the binding of cells to lectin-coated fibers

The ability of cells to bind to nylon fibers coated with lectin molecules interspaced with varying numbers of albumin molecules has been analyzed. The cells used were lymphoma cells, normal lymphocytes, myeloid leukemia cells, and normal and transformed fibroblasts, and the fibers were coated with different densities of concanavalin A or the lectins from soybean or wheat germ. Cells fixed with glutaraldehyde did not bind to lectin-coated fibers. The number of cells bound to fibers could be increased by increasing the density of lectin molecules on the fiber, the density of specific receptors on the cell, or the mobility of the receptors. It is suggested that binding of cells to fibers involves alignment and binding of specific cell surface receptors with lectin molecules immobilized on the fibers, and that this alignment requires short-range rapid lateral mobility (RLM) of the receptors. The titration of cell binding to fibers coated with different densities of lectin and albumin has been used to measure the relative RLM of unoccupied cell surface receptors for the lectin. The results indicate a relationship of RLM to lectin-induced cell-to-cell binding. The RLM or receptors for concanavalin A (Con A) was generally found to be higher than that of receptors for the lectins from wheat germ or soybean. Receptor RLM could be decreased by use of metabolic inhibitors or by lowering the temperature. Receptors for Con A had a lower RLM on normal fibroblasts than on SV40-transformed fibroblasts, and trypsinization of normal fibroblasts increased Con A receptor RLM. Normal lymphocytes, lymphoma cells, and lines of myeloid leukemia cells that can be induced to differentiate had a high receptor RLM, whereas lines of myeloid leukemia cells that could not be induced to differentiate had a low receptor RLM. These results suggest that the RLM of Con A receptors is related to the transformation of fibroblasts and the ability of myeloid leukemia cells to undergo differentiation     

Binding of purified lectins to guinea pig lymphocytes. Studies of the number, binding constant, and distribution of lens culinaris lectin A and Agaricus bisporus lectin molecules on lymphocyte surfaces

The surface membrane of guinea pig lymphocytes contains discrete receptors for several different homogeneous lectins. Two very similar lectins from the lentil, LcL-A and LcL-B, bind to the same receptor. Three other lectins, AbL, WGA, and Con A, do not bind detectably to the LcL receptor. AbL binds to another discrete receptor to which none of the other lectin molecules bind. The LcL and AbL receptors are contained on different units, each of which is capable of independent movement on the cell surface. The normal distribution of LcL molecules on the surface is different than the distribution of AbL molecules. However, when lymphocytes are simultaneously incubated with LcL and AbL, the distribution of bound LcL molecules on the cell surface parallels the normal distribution of AbL molecules, which indicates that the movement of AbL molecules and AbL receptors on the surface can strongly influence the movement of LcL and LcL receptors. When lymphocytes are held in close contact by LcL or AbL, the lectin molecules and receptors appear to concentrate at the area of contact between two cells. A model is presented which suggests that the migration of lectins and lectin receptors can occur by a multicellular process.     

Carbohydrate-protein interactions between HNK-1-reactive sulfoglucuronyl glycolipids and the proteoglycan lectin domain mediate neuronal cell adhesion and neurite outgrowth

Lecticans, a family of chondroitin sulfate proteoglycans, represent the largest group of proteoglycans expressed in the nervous system. We previously showed that the C-type lectin domains of lecticans bind two classes of sulfated cell surface glycolipids, sulfatides and HNK-1-reactive sulfoglucuronylglycolipids (SGGLs). In this paper, we demonstrate that the interaction between the lectin domain of brevican, a nervous system-specific lectican, and cell surface SGGLs acts as a novel cell recognition system that promotes neuronal adhesion and neurite outgrowth. The Ig chimera of the brevican lectin domain bind to the surface of SGGL-expressing rat hippocampal neurons. The substrate of the brevican chimera promotes adhesion and neurite outgrowth of hippocampal neurons. The authentic, full-length brevican also promotes neuronal cell adhesion and neurite outgrowth. These activities of brevican substrates are neutralized by preincubation of cells with HNK-1 monoclonal antibodies and by pretreatment of the brevican substrates with purified SGGLs. Brevican and HNK-1 carbohydrates are coexpressed in specific layers of the developing hippocampus where axons from entorhinal neurons elongate. Our observations suggest that cell surface SGGLs and extracellular lecticans comprise a novel cell-substrate recognition system operating in the developing nervous system.     

Distribution and mobility of lectin receptors on synaptic membranes of identified neurons in the central nervous system

The distribution and mobility of concanavalin A (Con A) and Ricinus communis agglutinin (RCA) receptors (binding sites) on the external surfaces of Purkinje, hippocampal pyramidal, and granule cells and their attached boutons were studied using ferritin-lectin conjugates. Dendritic fields of these cells were isolated by microdissection and gently homogenized. Cell fragments and pre- and postsynaptic membranes were labeled with the ferritin-lectin conjugates at a variety of temperatures, and the distribution of lectin receptors was determined by electron microscopy. Both classes of these lectin receptors were concentrated at nearly all open and partially open postsynaptic junctional membranes of asymmetric-type synapses on all three neuron types. Con A receptors were most concentrated at the junctional membrane region, indicating that the mature neuron has a specialized nonrandom organization of carbohydrates on its outer surface. Lectin receptors located on postsynaptic junctional membranes appeared to be restricted in their mobility compared to similar classes of receptors on extrajunctional membrane regions. Labeling with ferritin-RCA and - Con A at 37 degrees C produced clustering of lectin receptors on nonjunctional surfaces; however, Con A and RCA receptors retained their nonrandom topographic distribution on the postsynaptic junctional surface. The restricted mobility of lectin receptors was an inherent property of the postsynaptic membrane since the presynaptic membrane was absent. It is proposed that structures in the postsynaptic density may be transmembrane-linked to postsynaptic receptors and thereby determine topographic distribution and limit diffusion of specialized synaptic molecules. Speicalized receptor displays may play an important role in the formation and maintenance of specific synaptic contacts.     

Modulation of endothelial cell surface glycoconjugate expression by organ-derived biomatrices

Cell surface molecules play an important role in cellular communication, migration, and adherence. Here, we show the effect of organ-derived biomatrices on endothelial cell surface glycosylation. Five different lectins (with and without neuraminidase treatment) have been used as probes in an enzyme-linked lectin assay to quantitatively detect glycoconjugates on endothelial cells (BAEC) grown on tissue culture plastic or biomatrices isolated from bovine lung, liver, and kidney. BAEC generally exhibit strong binding of concanavalin A (Con A), Ricinus communis agglutinin I (RCA-I), wheat germ agglutinin (WGA), and soybean agglutinin, and peanut agglutinin after neuraminidase pretreatment of cells (Neu-SBA and Neu-PNA), while SBA and PNA consistently bind weakly to BAEC. BAEC grown on organ-derived biomatrices exhibit significantly altered binding intensities of Con A, RCA-I, WGA, and Neu-PNA: BAEC cultured on lung- or kidney-derived biomatrices express significantly stronger binding affinities for Con A and RCA-I than BAEC grown on liver-derived biomatrix or tissue culture plastic. In contrast, BAEC binding of WGA and PNA (after treatment of cells with neuraminidase) is significantly reduced when BAEC are grown on liver- or kidney-derived biomatrix. Quantitative lectin immunogold electron microscopy reveals consistently stronger lectin binding over nuclear regions compared to junctional regions between neighboring cells. These results indicate that extracellular matrix components regulate endothelial cell surface glycoconjugate expression, which determines cellular functions, e.g., preferential adhesion of lymphocytes or metastatic tumor cells.     

Lectin cell adhesion molecules (LEC-CAMs): a new family of cell adhesion proteins involved with inflammation.

The means by which leukocytes, including lymphocytes, monocytes, and neutrophils, migrate from the circulation to sites of acute and chronic inflammation is an area of intense research interest. Although a number of soluble mediators of these important cellular interactions have been identified, a major site of great importance to the inflammatory response is the physical interface between the white cell and the endothelium. This critical association is mediated by an array of cell surface adhesion molecules. Previous data have demonstrated that the integrin subfamily of heterotypic adhesion molecules was a major component of these adhesive interactions, although it was clear that other, non-integrin-like molecules of unknown identity also seemed to be involved during the inflammatory process. A number of these other cell-surface glycoproteins which may be involved with inflammation have recently been characterized by molecular cloning. These glycoproteins, including the peripheral lymph node homing receptor (pln HR), the endothelial cell adhesion molecule (ELAM), and PADGEM/gmp140, are all members of a family of proteins which are unified by the inclusion of three characteristic protein motifs: a lectin or carbohydrate recognition domain, an epidermal growth factor (egf) domain, and a variable number of short consensus repeats (scr) which are also found in members of the complement regulatory proteins. The appearance of lectin domains in all of these adhesion molecules is consistent with the possibility that these glycoproteins function by binding to carbohydrates which are expressed in a cell and/or region specific manner, and the members of this adhesion family have been given the generic name LEC-CAM (lectin cell adhesion molecules).(ABSTRACT TRUNCATED AT 250 WORDS)     

The fourth immunoglobulin-like domain of NCAM contains a carbohydrate recognition domain for oligomannosidic glycans implicated in association with L1 and neurite outgrowth

We have previously shown that the neural adhesion molecules L1 and NCAM interact with each other to form a complex which binds more avidly to L1 than L1 to L1 alone (Kadmon, G., A. Kowitz, P. Altevogt, and M. Schachner. 1990a. J. Cell Biol. 110:193-208). This cis-association between L1 and NCAM is carbohydrate-dependent (Kadmon, G., A. Kowitz, P. Altevogt, and M. Schachner. 1990b. J. Cell Biol. 110:209-218). In the present study, we report that L1 and NCAM bind to each other via oligomannosidic carbohydrates expressed by L1, but not by NCAM, as shown in several experiments: (a) complex formation between L1 and NCAM is inhibited by a mAb to oligomannosidic carbohydrates and by the oligosaccharides themselves; (b) NCAM binds to oligomannosidic carbohydrates; (c) within the L1/NCAM complex, the oligomannosidic carbohydrates are hidden from accessibility to a mAb against oligomannosidic carbohydrates; (d) the recombinant protein fragment of NCAM containing the immunoglobulin-like domains and not the fragment containing the fibronectin type III homologous repeats binds to oligomannosidic glycans. Furthermore, the fourth immunoglobulin-like domain of NCAM shows sequence homology with carbohydrate recognition domains of animal C-type lectins and, surprisingly, also with plant lectins. A peptide comprising part of the C-type lectin consensus sequence in the fourth immunoglobulin-like domain of NCAM interferes with the association between L1 and NCAM. The functional importance of oligomannosidic glycans at the cell surface was shown for neurite outgrowth in vitro. When neurons from early postnatal mouse cerebellum were maintained on laminin or poly-L-lysine, neurite outgrowth was inhibited by oligomannosidic glycans, by glycopeptides, glycoproteins, or neoglycolipids containing oligomannosidic glycans, but not by nonrelated oligosaccharides or oligosaccharide derivates. Neurite outgrowth was also inhibited by the peptide comprising part of the C- type lectin consensus sequence in the fourth immunoglobulin-like domain of NCAM. The combined results suggest that carbohydrate-mediated cis- associations between adhesion molecules at the cell surface modulate their functional properties.     

Growth-promoting alpha-globulin: a pleiotypic activator

Studies were made on the aggregation of trypsin-dissociated cells from chick embryos in the presence of Concanavalin A, a jackbean lectin, in its native tetrameric agglutinating form (n-ConA) and in a fragmented non-agglutinating form (t-ConA). The t-ConA was prepared by first trypsinizing native ConA and then subjecting the mixture to separation procedures to obtain and pool those fractions which failed completely to agglutinate cells. The presence of ConA in these fractions was demonstrated by equilibrium dialysis experiments using α-methyl-d-glycopyranoside which binds specifically to ConA. The agglutination of cells was conspicuously less in the presence of t-ConA + n-ConA than when n-ConA was added alone. The implication is that t-ConA competed with the untreated n-ConA for the same cell surface receptor sites and blocked them.The t-ConA at a final concentration of 200 μg/ml markedly inhibited the spontaneous aggregation of dissociated embryonic chick cells; the viability of these cells was unimpaired. This inhibitory effect was brought about by the t-ConA reacting with ConA sugar receptor sites. The results are correlated with current views on the possible way in which carbohydrates may be involved in cell-cell adhesion and a tentative explanation of how the t-ConA may be exerting its effect is put forward.     

Extracellular matrix and embryonal morphogenesis: role of fibronectin in cell migration

The neural crest provides a useful paradigm for cell migration and modulations in cell adhesion during morphogenesis. In the present review, we describe the major findings on the role of the extracellular matrix glycoprotein fibronectin and its corresponding integrin receptor in the locomotory behavior of neural crest cells. In vivo, fibronectin is associated with the migratory routes of neural crest cells and, in some cases, it disappears from the environment of the cells as they stop migrating. In vitro, neural crest cells show a great preference for fibronectin substrates as compared to other matrix molecules. Both in vivo and in vitro, neural crest cell migration can be specifically inhibited by antibodies or peptides that interfere with the binding of fibronectin to its integrin receptor. However, the migratory behavior of neural crest cells cannot result solely from the interaction with fibronectin. Thus, neural crest cells exhibit a particular organization of integrin receptors on their surface and develop a cytoskeletal network which differs from that of non-motile cells. These properties are supposed to permit rapid changes in the shape of cells and to favor a transient adhesion to the substratum. Recent findings have established that different forms of fibronectin may occur, which differ by short sequences along the molecule. The functions of most of these sequences are not known, except for 1 of them which carries a binding site for integrin receptors. We have demonstrated that this site is recognized by neural crest cells and plays a crucial role in their displacement. It is therefore possible that the forms of fibronectin carrying this sequence are not evenly distributed in the embryo, thus allowing migrating neural crest cells to orientate in the embryo. Fibronectin would then not only play a permissive role in embryonic cell motility, but have an instructive function in cell behavior.     

Lymphoblastoid cell adhesion mediated by a dimeric and polymeric endogenous beta-galactoside-binding lectin (galaptin).

Glutaraldehyde-polymerized human splenic galaptin, a beta-galactoside-binding lectin, was demonstrated to have enhanced hemagglutinating and asialofetuin binding activity relative to native dimeric galaptin when these lectins were present in solution. The polymerized lectin consisted primarily of 2-, 4- and 12-membered species after reductive alkylation. Both forms of galaptin bound, at 4 degrees C, to saturable B lymphoblastoid cell surface receptors. Estimates obtained by Scatchard analyses, with the binding data expressed in terms of 14.5 kDa subunit molarity, were 5 x 10(7) binding sites/cell with affinity constant Ka = 2.2 x 10(5) M for dimeric galaptin and 17 x 10(7) binding sites/cell with Ka = 3.4 x 10(5) M-1 for polymeric galaptin. Both forms of galaptin adsorbed to polystyrene with high efficiency; however, only plastic-adsorbed polymeric galaptin mediated adhesion of lymphoblastoid cells. Cell adhesion was inhibited by lactose. Plastic-adsorbed polymeric galaptin bound asialofetuin more efficiently than dimeric galaptin. Asialofetuin binding was inhibited 65% and 30-50% by lactose for plastic-adsorbed polymeric and dimeric galaptin, respectively. Native fetuin bound to the adsorbed dimeric galaptin in a lactose-insensitive manner. These data indicate that cell surface receptor-galaptin interaction is carbohydrate specific whereas polystyrene-adsorbed galaptin may demonstrate protein-protein interactions with soluble ligands.     

Cell surface beta 1,4-galactosyltransferase functions during neural crest cell migration and neurulation in vivo

Mesenchymal cell migration and neurite outgrowth are mediated in part by binding of cell surface beta 1,4-galactosyltransferase (GalTase) to N-linked oligosaccharides within the E8 domain of laminin. In this study, we determined whether cell surface GalTase functions during neural crest cell migration and neural development in vivo using antibodies raised against affinity-purified chicken serum GalTase. The antibodies specifically recognized two embryonic proteins of 77 and 67 kD, both of which express GalTase activity. The antibodies also immunoprecipitated and inhibited chick embryo GalTase activity, and inhibited neural crest cell migration on laminin matrices in vitro. Anti-GalTase antibodies were microinjected into the head mesenchyme of stage 7-9 chick embryos or cranial to Henson's node of stage 6 embryos. Anti-avian GalTase IgG decreased cranial neural crest cell migration on the injected side but did not cross the embryonic midline and did not affect neural crest cell migration on the uninjected side. Anti-avian GalTase Fab crossed the embryonic midline and perturbed cranial neural crest cell migration throughout the head. Neural fold elevation and neural tube closure were also disrupted by Fab fragments. Cell surface GalTase was localized to migrating neural crest cells and to the basal surfaces of neural epithelia by indirect immunofluorescence, whereas GalTase was undetectable on neural crest cells prior to migration. These results suggest that, during early embryogenesis, cell surface GalTase participates during neural crest cell migration, perhaps by interacting with laminin, a major component of the basal lamina. Cell surface GalTase also appears to play a role in neural tube formation, possibly by mediating neural epithelial adhesion to the underlying basal lamina.     

Developmentally regulated expression of cell surface carbohydrates during mouse embryogenesis

Cell surface carbohydrates undergo marked alterations during mouse embryogenesis. In preimplantation embryos, many carbohydrate markers show stage-specific expression in diverse ways. In early postimplantation embryos, certain carbohydrate markers are localized in defined regions in the embryo. Important carriers of stage-specific carbohydrates are the lactoseries structure (Gal beta 1----4GlcNAc) and the globoseries structure (Gal alpha 1----4Gal). Notably, the glycoprotein-bound large carbohydrate of poly-N-acetyllactosamine-type ([Gal beta 1----4GlcNAc beta 1----3]n) carries a number of markers preferentially expressed in early embryonic cells. These markers are of practical value in analyzing embryogenesis and cell differentiation. For example, in order to monitor in vitro differentiation of multipotential embryonal carcinoma cells, stage-specific embryonic antigen-1 (SSEA-1) and the Lotus agglutinin receptor have been used as markers of the undifferentiated cells, and the Dolichos agglutinin receptor has been used as a marker of extraembryonic endoderm cells. Developmental control of cell surface carbohydrates is attained by controlled expression of activities of key glycosyltransferases; for example, the activity of N-acetylglucosaminide alpha 1----3 fucosyltransferase is lost during in vitro differentiation of embryonal carcinoma cells to parietal endoderm cells, in parallel to the disappearance of SSEA-1. Accumulating evidence suggests that poly-N-acetyllactosamine-type glycans that are abundant in early embryonic cells are involved in cell surface recognition of these cells.     

The focal adhesion kinase--a regulator of cell migration and invasion

Cell migration plays an important role in embryonic development, wound healing, immune responses, and in pathological phenomena such as tissue invasion and metastasis formation. In this review, we summarize recent reports that connect the focal adhesion kinase (FAK) to cell migration and invasion. FAK is a nonreceptor protein tyrosine kinase involved in signal transduction from integrin-enriched focal adhesion sites that mediate cell contact with the extracellular matrix. Multiple protein-protein interaction sites allow FAK to associate with adapter and structural proteins allowing for the modulation of mitogen-activated protein (MAP) kinases, stress-activated protein (SAP) kinases, and small GTPase activity. FAK-enhanced signals have been shown to mediate the survival of anchorage-dependent cells and are critical for efficient cell migration in response to growth factor receptor and integrin stimulation. Elevated expression of FAK in human tumors has been correlated with increased malignancy and invasiveness. Because recent findings show that FAK contributes to the secretion of matrix-metalloproteinases, FAK may represent an important checkpoint in coordinating the dynamic processes of cell motility and extracellular matrix remodeling during tumor cell invasion.     

A role for fasciclin II in the guidance of neuronal migration.

The insect cell adhesion receptor fasciclin II is expressed by specific subsets of neural and non-neural cells during embryogenesis and has been shown to control growth cone motility and axonal fasciculation. Here we demonstrate a role for fasciclin II in the guidance of migratory neurons. In the developing enteric nervous system of the moth Manduca sexta, an identified set of neurons (the EP cells) undergoes a stereotyped sequence of migration along the visceral muscle bands of the midgut prior to their differentiation. Probes specific for Manduca fasciclin II show that while the EP cells express fasciclin II throughout embryogenesis, their muscle band pathways express fasciclin II only during the migratory period. Manipulations of fasciclin II in embryonic culture using blocking antibodies, recombinant fasciclin II fragments, and enzymatic removal of glycosyl phosphatidylinositol-linked fasciclin II produced concentration-dependent reductions in the extent of EP cell migration. These results support a novel role for fasciclin II, indicating that this homophilic adhesion molecule is required for the promotion or guidance of neuronal migration.     

Role of CD11/CD18 in adhesion and transendothelial migration of T cells. Analysis utilizing CD18-deficient T cell clones.

The role of leukocyte function-associated Ag-1 (LFA-1) (CD11a/CD18) in T cell-endothelial cell (EC) interactions was assessed by utilizing CD11a/CD18-deficient T cell clones generated from a patient with leukocyte adhesion deficiency (LAD). The ability of these clones to bind to and migrate through monolayers of EC in vitro was compared with that of clones generated in a similar manner from normal controls. The LAD clones bound to EC to a similar extent as the controls. The contribution of other cell surface adhesion molecules was assessed with mAb blocking experiments. It was found that part of the EC binding by these CD11a/CD18-deficient clones was mediated by an interaction of very late Ag-4 (VLA-4) with vascular cell adhesion molecule-1 (VCAM-1) on the EC. In contrast to their normal ability to bind to EC, the capacity of the LAD clones to migrate through EC monolayers was significantly less than that of the control clones. This impairment in migration was not related to decreased intrinsic motility. Moreover, neither phorbol ester stimulation of the LAD clones nor IL-1 stimulation of the EC increased the capacity of the clones to migrate through EC monolayers, although binding to EC was augmented by both treatments. Only a minimal percentage of the migration of either control or LAD clones was inhibited by mAb to VLA-4 or VCAM-1. These data demonstrate that LFA-1 plays a central role in the transendothelial migration of T cells. In the absence of LFA-1, T cells retain the ability to bind to EC because of the activity of other receptor/ligand pairs, including VLA-4/VCAM-1. Finally, it is likely that, during both binding and transendothelial migration of T cells, additional cell surface molecules play a role.     

Directed migration of cells from the sponge Geodia cydonium

The migration behavior of cells from the sponge Geodia cydonium was studied in vitro, applying the 'Tissue Culture Slide Chamber' technique. The homologous lectin caused a directed cell migration with a maximal locomotory rate of 1.6 mum/min. Competition experiments using the solubilized lectin receptor (= antiaggregation receptor) revealed that the chemotactic ligand (= lectin) interacts directly with the lectin receptor which-in consequence-functions as the chemotactic receptor. The ability of the lectin to promote cell migration is abolished by coincubation with purified leucine aminopeptidase. Biochemical and immunochemical data revealed that this enzyme is present also on the surface of sponge cells. Furthermore, we present evidence that the chemotactic receptor (= anti-aggregation receptor) on the cell surface is, in an hitherto unknown manner, coupled with the intracellularly present actin filaments. From these data we conclude that the directed migration of Geodia cells is mediated by the interaction between the lectin (= chemotactic ligand) and the lectin receptor (= chemotactic receptor); it is very likely that also intracellular structural elements operate simultaneously and coordinately during cell migration.