To evaluate the potential role of human placental endothelial cells in the transport of IgG from maternal to fetal circulation, we studied Fcγ receptor (FcγR) expression by immunohistology and immunoblotting. Several pan-FcγRII Abs that label the placental endothelium displayed a distribution pattern that correlated well with transport functions, being intense in the terminal villus and nil in the cord. In contrast, the MHC class 1-like IgG transporter, FcRn, and the classical FcγRIIa were not expressed in transport-related endothelium of the placenta. Our inference, that FcγRIIb was the likely receptor, we confirmed by analyzing purified placental villi, enriched in endothelium, by immunoblotting with a new Ab specific for the cytoplasmic tail of FcγRIIb. These experiments showed that the FcγRII expressed in villus endothelium was the b2 isoform whose cytoplasmic tail is known to include a phosphotyrosyl-based motif that inhibits a variety of immune responses. We suggest that this receptor is perfectly positioned to transport IgG although as well it may scavenge immune complexes.

Epithelial cells lining the urinary tract are rich in globo series glycolipids, structurally defined by a Gal␣1,4Gal motif in the oligosaccharide moiety of this glycolipid family. This Gal␣1,4Gal motif is the attachment target for the P-fimbrial adhesin of uropathogenic Escherichia coli. We investigated the ability of a trisaccharide analog of this core motif, globotriose (Gal␣1,4Gal␤1,4Glc), to interfere with uropathogen attachment and colonization in vitro and in vivo. We assessed the ability of globotriose to inhibit and reverse the binding and agglutination of a P-fimbriated strain of E. coli (JR1) using human erythrocytes and immortalized human colonic epithelial cells as targets. Globotriose (5 mg/ml) completely inhibited and reversed cell agglutination and caused a 10-to 100-fold reduction in JR1 binding to target cells, as determined by flow cytometry. In preparation for an in vivo efficacy study, we investigated the distribution and pharmacokinetics of globotriose in the BALB/c mouse. Globotriose was administered via the tail vein, targeting an instantaneous plasma concentration of 5 mg/ml, and in a different experiment, animals were gavaged at 10 times the intravenous (i.v.) dose. Globotriose was rapidly cleared from plasma (half-life [t 1/2 ], 6 min) and slowly excreted via the kidney (t 1/2 , 4 h). Urine levels of >5 mg/ml were maintained from 4 to 12 h after the i.v. bolus dose, which resulted in a 1-log reduction in established bladder colonization by JR1. These results suggest that free, soluble globotriose is a feasible alternative therapy for urinary tract infections.Glycolipids and other cell surface glycoconjugates play important roles in tissue development, cell trafficking and sorting, and cell-cell recognition. Independently of their inherent biological functions, cell surface glycolipids are used as targets by bacteria, viruses, and toxins to recognize and adhere to cells. Several groups have described and proposed the use of oligosaccharides to prevent or reverse pathological events occurring at the cell surface (7,14,15). This oligosaccharide receptor decoy concept is based on a rich body of experimental evidence demonstrating the importance of cell surface oligosaccharides in health and disease. Microbial lectins have been shown to have low affinities for their monovalent carbohydrate binding targets (4, 5), and carbohydrate targets of microbial lectins are normally present in a multivalent fashion on mammalian cell surfaces. The microbial lectins themselves are often displayed as multivalent complexes, or, as is the case with many microbial toxins, each contains a multimeric carbohydrate binding subunit. This multivalent presentation of binding targets and microbial lectins drives the equilibrium strongly in favor of the formation of target-ligand pairs. For these reasons, multivalent glycoconjugates have been favored for development as antiadhesive therapeutic candidates, despite the difficulties associated with the synthesis and the poor bioavailability of multivalent preparations.Re...

Gap junctional intercellular communication (GJIC) is reduced in many neoplastic cells, but few data exist for esophageal neoplasms. GJIC was examined by fluorescent dye microinjection in two nontumorigenic and two highly tumorigenic rat esophageal epithelial cell lines. All lines expressed high levels of dye coupling in homologous cell culture. In cocultures of nontumorigenic and tumorigenic cells, however, only one of six cell combinations displayed significant heterologous GJIC. Northern, Western, and immunohistochemical analyses indicated that all four cell lines expressed comparable levels of connexin43 (Cx43), but not connexin32 or connexin26, and formed Cx43-containing gap junction plaques at cell-cell interfaces. Immunostaining of rat esophageal frozen sections demonstrated that esophageal epithelial cells expressed Cx43 in vivo. In normal epithelium, the highest expression was seen in the basal cells and little suprabasal staining was evident. In preneoplastic and neoplastic lesions of the esophageal epithelium which were induced by treating rats with N-nitrosomethylbenzylamine, Cx43 staining of the basal layer was also seen but appeared to be more diffuse compared to normal epithelium. In addition, suprabasal Cx43 staining was apparent in dysplastic and papillomatous lesions. These results indicate that Cx43 is expressed in normal and neoplastic rat esophageal cells and that the cells exhibit extensive homologous GJIC, but little heterologous GJIC. This lack of heterologous GJIC may be due to differences in cell adhesion proteins or other factors.