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.     

Properties of the human erythrocyte membrane receptors for peanut and Dolichos biflorus lectins.

Neuraminidase treatment of blood type A and B human erythrocytes, which is required for the agglutination of these cells by peanut (Arachis hypogaea) lectin, increased the number of receptor sites for the lectin from about 5 × 10⁴ to 1.8 × 10⁶ sites/ cell for both blood types. The same treatment also increased the agglutinability of type A cells by the blood group A-specific Dolichos biflorus lectin, but the number of receptor sites for this lectin (~6 × 10⁵ sites/cell) did not change. D. biflorus lectin binding and agglutination of blood type B cells were negligible both before and after neuraminidase treatment. To isolate the peanut agglutinin receptor from the membrane of these cells, washed type A erythrocytes were incubated with neuraminidase and galactose oxidase and then treated with NaB³H₄, thus labeling the galactose residues on the membrane. For measuring peanut agglutinin receptor activity, a radioaffinity assay was developed based on the displacement of [¹⁴C]asialofetuin from peanut agglutinin by receptor and precipitation of the complex in the presence of polyethyleneglycol. Membranes were isolated by hypotonic lysis and were solubilized in 0.5% Empigen BB, a zwitterionic detergent, which was found to be superior to Triton X-100 for this purpose. The cell extract, after centrifugation, was subjected to affinity chromatography on peanut agglutinin-polyacrylhydrazido-Sepharose. Elution with lactose afforded a peak of radioactivity (32% yield) containing 70% of the applied receptor activity. The eluting sugar and the receptor were separated by chromatography on Bio-Gel P-2 with subsequent dialysis against 80% acetone to remove the detergent. The bulk of the isolated receptor radioactivity (91%) precipitated with peanut agglutinin. The amino acid composition, the glucosamine and galactosamine content and the electrophoretic mobility, on polyacrylamide gel electrophoresis in sodium dodecyl sulfate of the peanut receptor were similar to those of asialoglycophorin. In addition, the peanut receptor coprecipitated with asialoglycophorin and with isolated erythrocyte T antigen on Ouchterlony double-diffusion plates against peanut agglutinin and the Ricinus communis lectin, but not with D. biflorus lectin, suggesting that the receptor for the latter lectin is distinct from the peanut agglutinin receptor.     

A study of metabolic cooperation with established myoblast cell lines.

The present study was undertaken to test the action of ConA on the distribution of intramembranous particles (IMPs) and on the reassembly of junctional contacts in isolated and reaggregated embryonic neuronal and glial cells. The lectin ConA causes all embryonic cells to aggregate in unorganized cell patterns. ConA does not alter the distribution of IMPs but it inhibits the formation of the zonula occludens (ZO) by preventing the alignment and fusion of IMPs or by inducing them to become arranged in bizarre arrays. The possible relationship between ConA receptor sites and the IMPs is discussed. From a morphological viewpoint the aggregation of embryonic cells influenced by lectin is distinctly different from the normal processes of cell adhesion, cell sorting and establishment of intercellular contacts.     

Characterization of the galactose-specific binding activity of a purified soluble Entamoeba histolytica adherence lectin.

We studied galactose (Gal)-specific binding of the soluble purified 260-kDa Entamoeba histolytica adherence protein to glycosylation deficient Chinese hamster ovary (CHO) cell mutants. Our goal was to further define the lectin's functional activity and carbohydrate receptor specificity. The adherence protein was purified by acid elution from an immunoaffinity column; however, exposure of the surface membrane lectin on viable trophozoites to identical acid pH conditions had no effect on carbohydrate binding activity. Saturable Gal-specific binding of soluble lectin to parental CHO cells was demonstrated at 4 degrees C by radioimmunoassay; the dissociation coefficient (Kd) was 2.39 x 10(-8) M-1 with 5.97 x 10(4) lectin receptors present per CHO cell. Gal-specific binding of lectin to Lec2 CHO cell mutants, which have increased N- and O-linked terminal Gal residues on cell surface carbohydrates, was increased due to an enhanced number of receptors (2.41 x 10(5)/cell) rather than a significantly reduced dissociation constant (4.93 x 10(-8) M-1). At 4 degrees C, there was no measurable Gal-specific binding of the adherence protein to the Lec1 and 1dlD.Lec1 CHO mutants, which contain surface carbohydrates deficient in terminal Gal residues. Binding of lectin (20 micrograms/ml) to CHO cells was equivalent at 4 degrees C and 37 degrees C and unaltered by adding the microfilament inhibitor, Cytochalasin D (10 micrograms/ml). Gal-specific binding of the lectin at 4 degrees C was calcium independent and reduced by 81% following adsorption of only 0.2% of the lectin to CHO cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

The murine IL 2 receptor. III. Cellular requirements for the induction of IL 2 receptor expression on T cell subpopulations

The accessory cell requirements for the induction of the IL 2 receptor by the lectin Con A on murine T cell subsets were directly assayed with anti-IL 2 receptor monoclonal antibodies. Substantial levels of IL 2 receptor expression were induced on T lymphocytes of the MHC class I-restricted, suppressor/cytotoxic phenotype (L3T4-, Ly-2+) in the presence and absence of accessory cells. In contrast, high levels of IL 2 receptor expression could only be induced on T cells of the MHC class II-restricted, helper/inducer phenotype (L3T4+, LY-2-) in the presence, but not in the absence, of accessory cells. Ia- cells such as the P388D1 macrophage line or cultured fibroblasts (DAP X 3) were as efficient as the Ia+ B cell hybridoma LB in providing accessory cell function for the L3T4+, Ly-2- subset. PMA, but not purified human IL 1, could substitute for accessory cells for both IL 2 receptor expression and IL 2 secretion by the L3T4+, Ly-2- subset. These data suggest that IL 2 receptor induction on the L3T4+, Ly-2- subset is complex, possibly requiring a T cell-accessory cell interaction, whereas the lectin may directly trigger IL 2 receptor expression on L3T4-, Ly-2+ T cells.     

Binding of Erythroagglutinating Phytohemagglutinin Lectin from Phaseolus vulgaris to the Epidermal Growth Factor Receptor Inhibits Receptor Function in the Human Glioma Cell Line, U373 MG

Abstract: Little is known about the role of the N -linked oligosaccharides in the function of the epidermal growth factor (EGF) receptor (EGF-R). In a human glioma cell line, U373 MG, EGF-Rs contain the bisecting N -linked oligosaccharide sequence recognized by erythroagglutinating phytohemagglutinin lectin from Phaseolus vulgaris (E-PHA). Incubation of E-PHA with cultured U373 MG cells results in inhibition of EGF binding to its receptor and consequently inhibition of EGF-induced autophosphorylation of the receptor. Consistent with the inhibitory effects on the EGF-R, phenotypic events that depend on EGF-R signaling, such as cell spreading and proliferation, were also found to be modified. The effect of this lectin seems to be specific because leukoagglutinating phytohemagglutinin lectin from P. vulgaris (L-PHA), an isolectin of E-PHA, had no effect on EGF-R activity or the biological functions of these cells even though L-PHA was able to bind to the EGF-R. These findings suggest the presence of an important bisecting N -linked oligosaccharide structure in close proximity to the EGF binding site on the receptor. Furthermore, these results suggest the possibility that E-PHA lectin binding may provide an additional approach to blocking EGF-dependent glioma cell growth.     

A new lectin in red kidney beans called PvFRIL stimulates proliferation of NIH 3T3 cells expressing the Flt3 receptor

A new legume lectin has been identified by its ability to specifically stimulate proliferation of NIH 3T3 fibroblasts expressing the Flt3 tyrosine kinase receptor. The lectin was isolated from conditioned medium harvested from human peripheral blood mononuclear cells activated to secrete cytokines by a crude red kidney bean extract containing phytohemagglutinin (PHA). Untransfected 3T3 cells and 3T3 cells transfected with the related Fms tyrosine kinase receptor do not respond to this lectin, which we called PvFRIL (Phaseolus vulgaris Flt3 receptor-interacting lectin). When tested on cord blood mononuclear cells enriched for Flt3-expressing progenitors, purified PvFRIL fractions maintained a small population of cells that continued to express CD34 after 2 weeks in suspension cultures containing IL3. These cultures did not show the effects of IL3's strong induction of proliferation and differentiation (high cell number and exhausted medium); instead, low cell number at the end of the culture period resulted in persistence of cells in the context of cell death. These observations led to the hypothesis that PvFRIL acts in a dominant manner to preserve progenitor viability and prevent proliferation and differentiation.     

Combination of immunological and lectin reactions in affinity histochemistry: proposition of the term affinitin.

Using the series system cell receptor leads to mistletoe lectin leads to antiferritin-antibody leads to ferritin, the possibilities for combination of lectin and immunological reactions for histochemistry are discussed. The system cell antigen leads to antibody leads to labelled mistletoe (or other) lectin is recommended for visualization of cell antigens (mistletoe lectin as common immunoglobulin reagent). It is pointed out that lectin reactions do not belong to immunhistochemistry but to affinity histochemistry. For all receptor specific proteins (antibodies, lectins, enzymes, haptoglobin and other) the term affinitin is proposed. In consideration of this new definition a common scheme is formulated: Affinitin reacts with affinitin receptor forming affinity product.     

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.     

Properties of enucleated cells. III. Changes in cytoplasmic architecture of enucleated BHK21 cells following trypsinization and replating.

At low concentrations of concanavalin A (conA), binding of the lectin to the erythrocytes appears to be the rate-limiting step in the agglutination of these cells. At higher concentrations of lectin the rate of agglutination is concentration-independent, indicating that the aggregation reaction is rate-determining. Only 5 to 7% of the 1.2 × 10⁵ receptor sites need be occupied by con A in order for agglutination to take place. Although trypsin-treated cells bind 30% less ¹²⁵I-conA, they agglutinate better than untreated cells. At high lectin concentrations, erythrocyte agglutination by wheat germ agglutinin (WGA) is more than 8 times faster than the conA-mediated reaction. Lowering of the temperature to 0 °C reduces the rate but not the extent of the agglutination by both lectins. Mechanical shear reduced the conA-mediated agglutination of native cells by more than 160-fold and that of trypsinized and neuraminidase-treated cells 6-fold and 4-fold, respectively.It is concluded that metabolic activity, receptor mobility (i.e. cluster or patch formation) and cytochalasin B-sensitive processes, all of which have been reported to be involved in the lectin-mediated agglutination of fibroblasts and other cells, do not play a role in erythrocyte agglutination. Lectin-mediated erythrocyte agglutination appears to be governed primarily by the rate and extent of binding of lectin to the cell surface, the cell surface charge (modifiable by enzyme treatments or polycations) and the shear forces in the suspension. Morphological studies confirm and amplify these conclusions.     

Homologous liver parenchymal cell-cell adhesion mediated by an endogenous lectin and its receptor

Many studies have implicated cell-surface lectins in heterologous cell-cell adhesion, but little is known about the participation of lectins in cellular adhesion in homologous cells. Here, we show the development of a cell model for investigating the direct role of a cell-surface lectin in homologous cell-cell adhesion. Parenchymal cells were isolated from caprine liver using a perfusion buffer, and dispersed in a chemically defined modified Ringer’s solution. These cells undergo autoagglutination in the presence of Ca²⁺. The autoagglutinated cells can be dissociated specifically with D-galactose (50 mM), which also inhibits the liver cell autoagglutination event. The blood serum protein fetuin has no effect on liver cell autoagglutination, whereas desialylated fetuin (100 μM), with its terminal D-galactose residue, showed a high affinity for blocking the autoagglutination event. The data demonstrates the occurrence of a Ca²⁺-dependent D-galactose-specific lectin and a lectin receptor on the parenchymal cells. Furthermore, it shows that the observed autoagglutination event is caused by the interaction of the cell-surface lectin with its receptor on the neighbouring homologous cells. The data supports the view that homologous cell-cell contact in mammalian tissues is triggered by such lectin-receptor interaction and that the previously reported cell-surface adhesive proteins serve as a secondary force to strengthen cell adhesion. This cell model could be extremely useful for investigating the direct role of cell-surface lectin and its receptor in homologous cell adhesion in a variety of tissues under normal and pathological conditions.     

Mode of cell surface marker changes during retinoic acid-induced differentiation in pluripotent embryonal carcinoma cells

Pluripotent teratocarcinoma cell line, 311, was cultured in the presence of retinoic acid (RA) and studied for the processes of early marker changes associated with cell differentiation. The cell populations that have lost peanut agglutinin (PNA), Lotus tetragonolobus agglutinin (LTA) or wheat germ agglutinin (WGA) receptor increased in proportion to the period since the start of RA treatment. The kinetics of the appearance of these receptor-negative cell populations suggests that the differentiating cells lose lectin receptors in the order of PNA, LTA and WGA. However, the changes in F9 antigen(s) and LTA receptor occurred at an equal frequency in PNA+ and PNA- cells, indicating that, although the loss of lectin receptors takes place in a distinct order, the change in each receptor itself proceeds independently of the state of other lectin receptors.     

N-linked oligosaccharides of the murine transferrin receptor from a plasmacytoma cell line. Comparison with total cellular N-glycans

The N-linked oligosaccharides synthesised by the murine plasmacytoma cell line NS-1 have been analysed by lectin affinity chromatography on columns of immobilised concanavalin A (Con A), Lens culinaris (lentil), Ricinus communis agglutinin (RCA) and leuko-phytohemagglutinin (L-PHA). The majority of complex N-glycans in this transformed cell line were branched structures with only a low level of biantennary complex chains detected. The analysis showed the major complex N-glycan fraction consisted of a minimum sialylated triantennary structure. [3H]Mannose-labelled transferrin receptor was isolated from NS-1 cells by immunoprecipitation followed by electroelution from SDS polyacrylamide gels. The isolated receptor was digested with Pronase and the 3H-labelled glycopeptides analysed by lectin affinity chromatography. Analysis by Con A-Sepharose indicated that approx. 50% of the labelled glycopeptides were branched complex N-glycans (unbound fraction) while the remainder were oligomannose structures (strongly bound). The presence of tri and/or tetraantennary structures in the Con A unbound fraction was further suggested by the interaction of 61% of the fraction with L-PHA. The lectin profiles obtained for the complex N-glycans of the transferrin receptor glycopeptides were similar to those for the total cellular glycopeptides of NS-1 cells. Reverse-phase HPLC analysis of tryptic glycopeptides of the isolated [3H]mannose-labelled transferrin receptor gave three 3H-labelled peaks, indicating that all three potential N-glycosylation sites on the receptor are utilised. The Con A-Sepharose profiles of the three fractions indicated the presence of branched complex N-glycans and high mannose chains at each site. The profiles of two of the tryptic glycopeptide fractions were very similar, while the third had a higher content of oligomannose oligosaccharides.     

Hepatocyte adhesion to carbohydrate-derivatized surfaces. I. Surface topography of the rat hepatic lectin

The rat hepatic lectins, galactose- and N-acetylgalactosamine-binding proteins found on the hepatocyte cell surface, mediate adhesion of isolated primary rat hepatocytes to artificial galactose-derivatized polyacrylamide gels. Biochemical and immunohistochemical techniques were used to examine the topographical redistribution of the rat hepatic lectins in response to galactose-mediated cell adhesion. Hepatocytes isolated from rat liver by collagenase perfusion had an average of 7 x 10(5) cell surface lectin molecules per cell, representing 30-50% of the total lectin molecules per cell, the remainder residing in intracellular pools. Hepatocytes incubated on galactose-derivatized surfaces, whether at 0-4 degrees C or 37 degrees C, rapidly lost greater than 80% of their accessible cell surface lectin binding sites into an adhesive patch of characteristic morphology. The kinetics of rat hepatic lectin disappearance were used to estimate a lateral diffusion coefficient greater than 9 x 10(-9) cm2/s at 37 degrees C, suggesting rapid and unimpeded lectin diffusion in the plane of the membrane. Indirect immunofluorescence labeling of adherent cells using antihepatic lectin antibody revealed a structured ring of receptors surrounding an area of exclusion (patch) of reproducible size and shape which represented approximately 8% of the hepatocyte cell surface. Notably, adherent cells, which had lost greater than 80% of their accessible surface binding sites, still endocytosed soluble galactose-terminated radioligand at greater than 50% of the rate of nonadherent control cells. No net movement of rat hepatic lectin from intracellular pools to the cell surface was found on cells recovered after adhesion to galactose-derivatized surfaces at 37 degrees C, suggesting that the physical size and/or lectin density of the patch was restricted by kinetic or topological constraints.     

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     

Serologically defined subpopulations of human T lymphocytes.

Several rabbit antisera to T cells obtained from various sources (thymus, peripheral blood, brain, T-derived leukemias) were studied with the aim to obtain reagents specific for a subset of T cells. Sera were first absorbed on human tissues and B cells; thereafter these T cell-specific sera were additionally absorbed with T cells of different origin and especially with leukemic T cells, which are likely to represent a clonal expnasion of a subset of T cells with potentially unique antigenic markers. Three antigenically distinct subpopulations of T cells were delineated. The relationship of these subsets with previously defined human T cell subpopulations (T subsets with a receptor for the Fc or IgG or IgM or with a receptor for a lectin from wheat germ agglutinin) was investigated.     

Ricin toxicity to microglial and monocytic cells.

Microglial cells, like macrophages, are very sensitive to ricin, a galactose-specific toxic lectin belonging to the family of ribosome-inactivating proteins. This toxin can be taken up by most cells through the binding of its B chain to galactose-containing molecules on the cell membrane. In macrophagic cell types it can be internalised also by mannose receptors which are present on the surface of these cells. Endocytosis of the toxin by either pathway was evaluated by ricin toxicity to primary cultures of rat microglial cells and to a microglial N11 cell line in the presence or absence of lactose and mannan, which compete for the endocytosis via the ricin lectin chain or cellular mannose receptors, respectively. Results were compared with those obtained in cultures of mouse macrophages, human monocytes, and a monocytic JM cell line. All cultures were protected from ricin toxicity more by lactose than by mannan, indicating that ricin endocytosis via its lectin B chain is prevalent over that mediated by cellular mannose receptors. However, a partial protection by mannan was observed in all cases but not-stimulated N11 cells, either in the form of direct protection or of significant additional protection over that afforded by lactose. Mannose receptor expression by N11 cells was negative before, and positive after, treatment with endotoxin, as assessed by the specific binding of 125I-mannose-bovine serum albumin. Moreover, a partial protection from ricin toxicity by mannan was induced in the N11 microglial line after stimulation, consistently with an inducible expression of the mannose receptor by activated cells switched towards a microglial phenotype.     

The effect of amphotericin B on lectin-induced aggregation of cell surface receptors

The mobility of concanavalin A (ConA) and ricin receptors from NS20 neuroblastoma and C₆ glioma cells was studied using an electrophoretic technique. Cells attached to a solid support were exposed to an electrical field (12V cm⁻¹) at room temperature. The distribution of lectin receptors on the cell surface was revealed by fluorescent conjugates of lectins and microscopic observation of the fixed cells. This technique allowed the estimation of the mobilities of lectin receptors either in free or liganded form, depending on the time at which the cells are labeled with lectins (either after or before electrophoresis). In line with previous observations [1] it is shown that in their free form ConA and ricin receptors are mobile all over the cell surface. Ligand binding induced an apparent receptor immobilization. Immobilization of ricin receptors from C₆ glioma cells could be induced either by the multivalent or the monovalent form of the lectin indicating that cross-linking of receptors by the ligand did not play a predominant role in the process of receptor immobilization. Amphotericin B but not ionophores like valinomycin or gramicidin blocked ligand-induced receptor immobilization. It is concluded from this observation that the effect of amphotericin B is not related to its ionophoretic properties but more likely to its capacity to interact with membrane cholesterol. When cells were incubated at 37 °C extensive patching of lectin receptors could be observed. This process was also inhibited by amphotericin B. A model is proposed to account for a role of cholesterol in ligand-induced receptor immobilization and patching.     

Immature human dendritic cells express asialoglycoprotein receptor isoforms for efficient receptor-mediated endocytosis.

In a search for genes expressed by dendritic cells (DC), we have cloned cDNAs encoding different forms of an asialoglycoprotein receptor (ASGPR). The DC-ASGPR represents long and short isoforms of human macrophage lectin, a Ca(2+)-dependent type II transmembrane lectin displaying considerable homology with the H1 and H2 subunits of the hepatic ASGPR. Immunoprecipitation from DC using an anti-DC-ASGPR mAb yielded a major 40-kDa protein with an isoelectric point of 8.2. DC-ASGPR mRNA was observed predominantly in immune tissues. Both isoforms were detected in DC and granulocytes, but not in T, B, or NK cells, or monocytes. DC-ASGPR species were restricted to the CD14-derived DC obtained from CD34(+) progenitors, while absent from the CD1a-derived subset. Accordingly, both monocyte-derived DC and tonsillar interstitial-type DC expressed DC-ASGPR protein, while Langerhans-type cells did not. Furthermore, DC-ASGPR is a feature of immaturity, as expression was lost upon CD40 activation. In agreement with the presence of tyrosine-based and dileucine motifs in the intracytoplasmic domain, mAb against DC-ASGPR was rapidly internalized by DC at 37 degrees C. Finally, intracellular DC-ASGPR was localized to early endosomes, suggesting that the receptor recycles to the cell surface following internalization of ligand. Our findings identify DC-ASGPR/human macrophage lectin as a feature of immature DC, and as another lectin important for the specialized Ag-capture function of DC.