Faculty Bibliography

We have used microchip format glycan array to characterize the individual carbohydrate recognition patterns by antibodies (Ab) in sera of 106 healthy donors. The glycan library included blood group antigens and other most frequent terminal oligosaccharides and their cores of mammalian N- and O-linked glycoproteins and glycolipids, tumor-associated carbohydrate antigens, and common components of bacterial/pathogenic polysaccharides and lipopolysaccharides, totally 205 glycans. The serum Ab interacted with at least 50 normal human glyco-motifs. Apart from expected blood group-, xeno- (heterophil) and infection-related binding activities, we observed a number of new and unexpected features. The surprising, relatively high antibody binding was found to the blood group P(1) and P(k) trisaccharides and H(type 2) trisaccharide. Novel and very high binding activities have been observed towards Galbeta1-3GlcNAc (Le(C)) related glycans, especially 3'-O-Su-Le(C), and towards 4'-O-sulfated lactosamine. Relatively high and uniform Ab binding to GalNAcalpha1-3Gal disaccharide demonstrated absence of correlation with fucosylated blood group A GalNAcalpha1-3(Fucalpha1-2)Gal antigen-similarly to well known relationship between Galalpha1-3Gal and true, fucosylated blood group B Galalpha1-3(Fucalpha1-2)Gal antigen. The binding intensity to Galalpha1-3Galbeta1-4GlcNAc xenoantigen was shown to be rather modest. Absence or very low Ab binding was found against oligosialic acid, sialooligosaccharides except SiaT(n), type 2 backbone glycans such as Le(y), and biantennary N-chain as well as its truncated forms, i.e. without terminal Sia, SiaGal, and SiaGalGlcNAc motifs. We have also found that Ab are capable of recognizing the short inner core typical for glycolipids (-Galbeta1-4Glc) and glycoproteins (-GalNAcalpha) as a fragment of bigger glycans

During thymocyte development, the T-cell receptor (TCR) can discriminate major histocompatibility complex (MHC)/peptide ligands over a narrow range of affinities and translate subtle differences into functional fate decisions. How small differences in TCR input are translated into absolute differences in functional output is unclear. We examined the effects of galectin-1 ablation in the context of class-I-restricted thymocyte development. Galectin-1 expression opposed TCR partial agonist-driven positive selection, but promoted TCR agonist-driven negative selection of conventional CD8(+) T cells. Galectin-1 expression also promoted TCR agonist-driven CD8alphaalpha intestinal intraepithelial lymphocytes (IEL) development. Recombinant galectin-1 enhanced TCR binding to agonist/MHC complexes and promoted a negative-selection-signaling signature, reflected in intensified rapid and transient extracellular signal-regulated kinase (ERK) activation. In contrast, galectin-1 expression antagonized ERK activity in thymocytes undergoing positive selection. We propose that galectin-1 aids in discriminating TCR-directed fate decisions by promoting TCR binding to agonist/MHC complexes and enforcing agonist-driven signals, while opposing partial-agonist signals. In this way, galectin-1 widens the distinction between TCR-directed functional fate cues

Here we describe a glycan microarray constructed by using standard robotic microarray printing technology to couple amine functionalized glycans to an amino-reactive glass slide. The array comprises 200 synthetic and natural glycan sequences representing major glycan structures of glycoproteins and glycolipids. The array has remarkable utility for profiling the specificity of a diverse range of glycan binding proteins, including C-type lectins, siglecs, galectins, anticarbohydrate antibodies, lectins from plants and microbes, and intact viruses

Galectins are a family of beta-galactose binding lectins associated with functions such as immunological and malignant events. To study the binding affinity of galectins for natural and artificial saccharides and glycoconjugates we have developed an assay using fluorescence polarization. A collection of fluorescein-conjugated saccharides was synthesized and used as probes with galectins-1 and -3 and the two carbohydrate recognition domains of galectin-4. Direct binding of a fixed probe amount with different amounts of each galectin defined specificity and selectivity and permitted selection of the optimal probe for inhibition studies. Then fixed amounts of galectin and selected probe were used to screen the inhibitory potency of a library of nonfluorescent compounds. As the assay is in solution and does not require separation of free and bound probe, it is simple and rapid and can easily be applied to different unlabeled galectins. As all interaction components are known, K(d) values for galectin-inhibitor interaction can be directly calculated without approximation other than the assumption of a simple one-site competition

Galectin-4 belongs to a subfamily of galectins composed of two carbohydrate recognition domains within the same peptide chain. The two domains have all the conserved galectin signature amino acids, but their overall sequences are only approximately 40% identical. Both domains bind lactose with a similar affinity as other galectins, but their respective preferences for other disaccharides, and larger saccharides, are distinctly different. Thus galectin-4 has a property of a natural cross-linker, but in a modified sense since each domain prefers a different subset of ligands. Similarly to other galectins, galectin-4 is synthesized as a cytosolic protein, but can be externalized. During development and in adult normal tissues, galectin-4 is expressed only in the alimentary tract, from the tongue to the large intestine. It is often found in relatively insoluble complexes, as a component of either adherens junctions or lipid rafts in the microvillus membrane, and it has been proposed to stabilize these structures. Strong expression of galectin-4 can be induced, however, in cancers from other tissues including breast and liver. Within a collection of human epithelial cancer cell lines, galectin-4 is overexpressed and soluble in those forming highly differentiated polarized monolayers, but absent in less differentiated ones. In cultured cells, intracellular galectin-4 may promote resistance to nutrient starvation, whereas--as an extracellular protein--it can mediate cell adhesion. Because of its distinct induction in breast and other cancers, it may be a valuable diagnostic marker and target for the development of inhibitory carbohydrate-based drugs

Galectins are a family of beta-galactoside binding proteins that have been proposed as host receptors for bacteria because beta-galactoside carbohydrates are common in bacterial membrane glycolipid lipooligosaccharides (LOS) and lipopolysaccharides. We investigated the interaction of galectin-3 with gonococcal LOS that make lactosyl (Lc2 or Lac), paraglobosyl (nLc4; LNnT; lacto-N-neotetraose), gangliosyl (IV3GalNAcnLc4), and neolactohexaosyl (nLc6, lactonorhexaosyl) oligosaccharides. All but gangliosyl LOS terminate in beta-galactoside. Galectin-3 had the highest affinity for the nLc6 LOS, which is made by a strain that is highly infectious for the male urethra, but also bound nLc4 LOS and to a Lac LOS. The lacto-N-neotetraose tetrasaccharide was a more potent inhibitor of galectin-3 binding to LOS than either lactose or N-acetyllactosamine. The relative affinity of galectin-3 for gonococci mirrored its affinity for purified LOS. Western blot analysis revealed expression of galectin-3 by human endometrial adenocarcinoma and prostatic epithelial cells that can be invaded by gonococci. Immunohistochemistry of human fallopian tube epithelium showed localized expression of galectin-3 by non-ciliated cells, the specific cell gonococci invade in this tissue. We conclude that because of its location and affinity for gonococcal LOS galectin-3 could play a role in gonococcal infection

BACKGROUND & AIMS: Interleukin (IL)-10 is a cytokine with anti-inflammatory properties. The aim of this study was to explore the effect of a site-specific delivery of IL-10 on intestinal immune responses. METHODS: Transgenic mice were created in which IL-10 is expressed by the intestinal epithelial cells. RESULTS: Transgenic mice showed a marked increase in the number of intraepithelial lymphocytes in the small intestine. Mucosal lymphocytes of transgenic animals produced fewer T helper type 1 cytokines than wild-type lymphocytes. By contrast, the production of transforming growth factor beta was increased. Moreover, the epithelial layer in transgenic mice was significantly enriched for CD4(+)CD25(+) T cells. Furthermore, transgenic mice had increased numbers of immunoglobulin A-producing B cells in the small intestine. These effects were local because splenic lymphocytes were not affected. Studies in models of inflammatory bowel disease showed that transgenic IL-10 was able to attenuate the acute colitis induced by dextran sodium sulfate administration or by adoptive transfer of CD4(+)CD45RB(high) splenocytes, with a modest effect on the chronic intestinal inflammation arising spontaneously in IL-10(-/-) mice. CONCLUSIONS: These observations provide evidence for an in vivo lymphoepithelial cross talk, by which cytokines locally produced by epithelial cells can regulate immune responses in the intestine without systemic modifications