title: Human thymic epithelial cells express an endogenous lectin, galectin-1, which binds to core 2 O-glycans on thymocytes and T lymphoblastoid cells.
abstract: Thymic epithelial cells play a crucial role in the selection of developing thymocytes. Thymocyte-epithelial cell interactions involve a number of adhesion molecules, including members of the integrin and immunoglobulin superfamilies. We found that human thymic epithelial cells synthesize an endogenous lectin, galectin-1, which binds to oligosaccharide ligands on the surface of thymocytes and T lymphoblastoid cells. Binding of T lymphoblastoid cells to thymic epithelial cells was inhibited by antibody to galectin-1 on the epithelial cells, and by two antibodies, T305 and 2B11, that recognize carbohydrate epitopes on the T cell surface glycoproteins CD43 and CD45, respectively. T lymphoblastoid cells and thymocytes bound recombinant galectin-1, as demonstrated by flow cytometric analysis, and lectin binding was completely inhibited in the presence of lactose. The degree of galectin-1 binding to thymocytes correlated with the maturation stage of the cells, as immature thymocytes bound more galectin-1 than did mature thymocytes. Preferential binding of galectin-1 to immature thymocytes may result from regulated expression of preferred oligosaccharide ligands on those cells, since we found that the epitope recognized by the T305 antibody, the core 2 O-glycan structure on CD43, was expressed on cortical, but not medullary cells. The level of expression of the UDP-GlcNAc:Gal beta 1,3GalNAc-R beta 1, 6GlcNAc transferase (core 2 beta 1, 6 GlcNAc transferase, or C2GnT), which creates the core 2 O-glycan structure, correlated with the glycosylation change between cortical and medullary cells. Expression of mRNA encoding the C2GnT was high in subcapsular and cortical thymocytes and low in medullary thymocytes, as demonstrated by in situ hybridization. These results suggest that galectin-1 participates in thymocyte-thymic epithelial cell interactions, and that this interaction may be regulated by expression of relevant oligosaccharide ligands on the thymocyte cell surface.
authors.affiliation: Department of Pathology and Laboratory Medicine, UCLA School of Medicine 90024.
authors.forename: L G
authors.initials: LG
authors.lastname: Baum
authors.forename: M
authors.initials: M
authors.lastname: Pang
authors.forename: N L
authors.initials: NL
authors.lastname: Perillo
authors.forename: T
authors.initials: T
authors.lastname: Wu
authors.forename: A
authors.initials: A
authors.lastname: Delegeane
authors.forename: C H
authors.initials: CH
authors.lastname: Uittenbogaart
authors.forename: M
authors.initials: M
authors.lastname: Fukuda
authors.forename: J J
authors.initials: JJ
authors.lastname: Seilhamer
mesh_terms: D000818:Animals; D015703:Antigens, CD; D017252:CD3 Complex / Q000032:analysis; D002450:Cell Communication; D002648:Child; D004848:Epithelium / Q000737:chemistry; D037483:Galectin 1; D006388:Hemagglutinins / Q000032:analysis* / Q000502:physiology; D006801:Humans; D007223:Infant; D037102:Lectins / Q000032:analysis*; D017493:Leukocyte Common Antigens / Q000378:metabolism*; D051917:Leukosialin; D051379:Mice; D011134:Polysaccharides / Q000378:metabolism*; D011817:Rabbits; D012795:Sialoglycoproteins / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism*; D013950:Thymus Gland / Q000737:chemistry*
chemical_list: D015703:Antigens, CD; D017252:CD3 Complex; D037483:Galectin 1; D006388:Hemagglutinins; D037102:Lectins; D051917:Leukosialin; D011134:Polysaccharides; C465014:SPN protein, human; D012795:Sialoglycoproteins; C497863:Spn protein, mouse; D017493:Leukocyte Common Antigens