The antigen of bile canaliculi of the mouse hepatocyte: identification and ultrastructural localization

Carcinoembryonic antigen-related cell adhesion molecule 1 modulates experimental autoimmune encephalomyelitis via an iNKT cell-dependent mechanism

Carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1) is a CEA family member that has been reported to have an important role in the regulation of Th1-mediated colitis. In this study, we examined the role of CEACAM1 in an animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Treatment of C57BL/6J mice with CEACAM1-Fc fusion protein, a homophilic ligand of CEACAM1, inhibited the severity of EAE and reduced myelin oligodendrocyte glycoprotein-derived peptide (MOG(35-55))-reactive interferon-gamma and interleukin-17 production. In contrast, treatment of these animals with AgB10, an anti-mouse CEACAM1 blocking monoclonal antibody, generated increased severity of EAE in association with increased MOG(35-55)-specific induction of both interferon-gamma and interleukin-17. These results indicated that the signal elicited through CEACAM1 ameliorated EAE disease severity. Furthermore, we found that there was both a rapid and enhanced expression of CEACAM1 on invariant natural killer T cells after activation. The effect of CEACAM1-Fc fusion protein and anti-CEACAM1 mAb on both EAE and MOG(35-55)-reactive cytokine responses were abolished in invariant natural killer T cell-deficient Jalpha18(-/-) mice. Taken together, the ligation of CEACAM1 negatively regulates the severity of EAE by reducing MOG(35-55)-specific induction of both interferon-gamma and interleukin-17 via invariant natural killer T cell-dependent mechanisms.

The CD53 and CEACAM-1 genes are genetic targets for early B cell factor

Early B cell factor (EBF)-1 is a transcription factor known to be of critical importance for early B lymphocyte development. EBF-1 has been shown to directly interact with and regulate expression of a set of genes involved in the functional formation of the pre-B cell receptor, but the dramatic phenotype observed in the EBF-1-deficient mice suggests that several additional genes are activated by this protein. In order to identify additional target genes for EBF-1, we transduced a hematopoietic progenitor cell line, BaF/3, with an EBF-1-encoding retrovirus and investigated the induced gene expression pattern by micro-arrays. This analysis suggested that among others, the CD53 and the carcinoembryonic antigen-related cell adhesion molecule (CEACAM)-1 genes both were induced by ectopic expression of EBF-1. Identification of the 5' end of the cDNA enabled the identification of promoter elements with functional binding sites for EBF-1 and ability to respond to EBF-1 expression in transient transfection assays. These data suggest that CD53 and CEACAM-1 are direct genetic targets for EBF-1, providing additional information concerning the activity of this crucial transcription factor in hematopoiesis.

Mouse pregnancy-specific glycoproteins: tissue-specific expression and evidence of association with maternal vasculature

The pregnancy-specific glycoproteins (Psg) are secreted hormones encoded by multiple genes in rodents and primates, and are thought to act as immune modulators. The only Psg receptor identified is CD9, through which Psg17 induces cytokine production from macrophages cultured in vitro. We examined temporal and spatial aspects of Psg and CD9 expression during mouse pregnancy to determine whether their expression patterns support a role in immune modulation. Using in situ hybridisation, immunohistochemistry and RT-PCR we found Psg expression in trophoblast giant cells and in the spongiotrophoblast. Psg22 is the predominant Psg family member expressed in giant cells. Detectable Psg is associated predominantly with endothelial cells lining vascular channels in the decidua, rather than with maternal immune cell markers. CD9 expression exhibited partial overlap with Psg, but without exclusive co-localisation. CD9 was observed in decidual cells surrounding early implantation sites, and in the endometrium. However, embryo transfer of wild-type embryos to CD9-deficient females indicates that maternal CD9 is not essential for successful pregnancy.

Characterization of gastric adenocarcinoma cell lines established from CEA424/SV40 T antigen-transgenic mice with or without a human CEA transgene

Background

Gastric carcinoma is one of the most frequent cancers worldwide. Patients with gastric cancer at an advanced disease stage have a poor prognosis, due to the limited efficacy of available therapies. Therefore, the development of new therapies, like immunotherapy for the treatment of gastric cancer is of utmost importance. Since the usability of existing preclinical models for the evaluation of immunotherapies for gastric adenocarcinomas is limited, the goal of the present study was to establish murine in vivo models which allow the stepwise improvement of immunotherapies for gastric cancer.

Methods

Since no murine gastric adenocarcinoma cell lines are available we established four cell lines (424GC, mGC3, mGC5, mGC8) from spontaneously developing tumors of CEA424/SV40 T antigen (CEA424/Tag) mice and three cell lines derived from double-transgenic offsprings of CEA424/Tag mice mated with human carcinoembryonic antigen (CEA)-transgenic (CEA424/Tag-CEA) mice (mGC2^CEA, mGC4^CEA, mGC11^CEA). CEA424/Tag is a transgenic C57BL/6 mouse strain harboring the Tag under the control of a -424/-8 bp CEA gene promoter which leads to the development of invasive adenocarcinoma in the glandular stomach. Tumor cell lines established from CEA424/Tag-CEA mice express the well defined tumor antigen CEA under the control of its natural regulatory elements.

Results

The epithelial origin of the tumor cells was proven by morphological criteria including the presence of mucin within the cells and the expression of the cell adhesion molecules EpCAM and CEACAM1. All cell lines consistently express the transgenes CEA and/or Tag and MHC class I molecules leading to their susceptibility to lysis by Tag-specific CTL in vitro. Despite the presentation of CTL-epitopes derived from the transgene products the tumor cell lines were tumorigenic when grafted into C57BL/6, CEA424/Tag or CEA424/Tag-CEA-transgenic hosts and no significant differences in tumor take and tumor growth were observed in the different hosts. Although no spontaneous tumor rejection was observed, vaccination of C57BL/6 mice with lysates from gastric carcinoma cell lines protected C57BL/6 mice from tumor challenge, demonstrating the tumorigenicity of the tumor cell lines in nontransgenic mice of the H-2^b haplotype.

Conclusion

These tumor cell lines grafted in different syngeneic hosts should prove to be very useful to optimize immunotherapy regimens to be finally tested in transgenic animals developing primary gastric carcinomas.

Expression of nestin-green fluorescent protein transgene marks oval cells in the adult liver

Oval cells, which become apparent in the liver after chronic injury, serve as bipotent progenitors for differentiated hepatocytes and cholangiocytes. We found that, in the liver of adult transgenic mice in which expression of green fluorescent protein (GFP) is driven by regulatory elements of the nestin gene, the GFP signal marks a subpopulation of small epithelial cells that meet the criteria for oval cells, including morphology, localization, antigenic profile, and reactivity in response to injury. In the regenerating and developing liver, we also found nestin-GFP-positive cells that express hepatocyte markers; such cells may correspond to transiently appearing differentiating progeny of oval cells. During development, GFP-expressing cells in the liver emerge relatively late, after the appearance of differentiated hepatocytes and cholangiocytes. Our results suggest that nestin-GFP cells in the liver correspond to a specialized cell type whose primary function may be to serve as a reserve for adult liver epithelial cell types.

CEACAM1 is a potent regulator of B cell receptor complex-induced activation

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1, CD66a) is a member of the immunoglobulin (Ig) superfamily, previously characterized as an adhesion and signaling molecule in epithelial, endothelial, and hematopoietic cells. Here, we show that the CEACAM1 isoform expression pattern is different in nonactivated and activated primary mouse B lymphocytes and that CEACAM1 influences B cell receptor complex-mediated activation. A CEACAM1-specific monoclonal antibody strongly triggered proliferation of mouse B cells when combined with surface IgM cross-linking. However, anti-CEACAM1 was not mitogenic when added alone. The proliferation was more pronounced and lasted longer as compared with other activators of B cells, such as anti-IgM in the presence of interleukin-4 or lipopolysaccharide. A similar, costimulatory effect was exerted by CEACAM1-expressing fibroblasts, indicating that homophilic CEACAM1-CEACAM1 cell-mediated binding is the physiological stimulus for CEACAM1-triggered B cell signaling. The anti-CEACAM1/anti-IgM-activated cells aggregated in a lymphocyte function-associated antigen-1-dependent manner. Furthermore, cells that were activated by anti-CEACAM1/anti-IgM secreted Ig but did not go through Ig class-switching. Anti-CEACAM1 induced phosphorylation of c-Jun N-terminal kinase (stress-activated protein kinase) but did not activate the extracellular signal-regulated kinase or p38 mitogen-activated protein kinases.

CEACAM1 isoforms with different cytoplasmic domains show different localization, organization and adhesive properties in polarized epithelial cells

CEACAM1 is a signaling cell adhesion molecule expressed in epithelia,vessel endothelia and leukocytes. It is expressed as two major isoforms with different cytoplasmic domains. CEACAM1 occurs both in cell-cell contact areas and on apical surfaces of polarized epithelial cells, but it is not known how the different isoforms are distributed in polarized cells or what the functions of CEACAM1 are in the apical surfaces. We investigated the localization and organization of the two CEACAM1 isoforms in transfected,polarized MDCK cells by confocal microscopy and differential surface labelling. CEACAM1-L was found on both the apical and the lateral surfaces,whereas CEACAM1-S appeared exclusively on the apical surfaces. Maintenance of the lateral localization of CEACAM1-L required homophilic binding between CEACAM1-L molecules on adjacent cells. Double-labelling with anti-CEACAM1 antibodies directed against different epitopes indicated that apical CEACAM1-L occurred either in a homophilic adhesive state or in a free non-adhesive state. CEACAM1-S appeared almost exclusively in the homophilic adhesive state. These findings suggest that CEACAM1 mediates adhesive bonds between adjacent microvilli on the apical surfaces.

Helicobacter pylori-binding gangliosides of human gastric adenocarcinoma

Acidic and neutral glycosphingolipids were isolated from a human gastric adenocarcinoma, and binding of Helicobacter pylori to the isolated glycosphingolipids was assessed using the chromatogram binding assay. The isolated glycosphingolipids were characterized using fast atom bombardment mass spectrometry and by binding of antibodies and lectins. The predominating neutral glycosphingolipids were found to migrate in the di- to tetraglycosylceramide regions as revealed by anisaldehyde staining and detection with lectins. No binding of H. pylori to these compounds was obtained. The most abundant acidic glycosphingolipids, migrating as the GM3 ganglioside and sialyl-neolactotetraosylceramide, were not recognized by the bacteria. Instead, H. pylori selectively interacted with slow-migrating, low abundant gangliosides not detected by anisaldehyde staining. Binding-active gangliosides were isolated and characterized by mass spectrometry, proton nuclear magnetic resonance, and lectin binding as sialyl-neolactohexaosylceramide (NeuAcalpha3Galbeta4GlcNAcbeta3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer) and sialyl-neolactooctaosylceramide (NeuAcalpha3Galbeta4GlcNAcbeta3Galbeta4GlcNAcbeta3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer).

Carcinoembryonic Antigen-Related Cell Adhesion Molecule 1 on Murine Dendritic Cells Is a Potent Regulator of T Cell Stimulation

Dendritic cells (DC) are important APCs that play a key role in the induction of an immune response. The signaling molecules that govern early events in DC activation are not well understood. We therefore investigated whether DC express carcinoembryonic Ag-related cell adhesion molecule 1 (CEACAM1, also known as BGP or CD66a), a well-characterized signal-regulating cell-cell adhesion molecule that is expressed on granulocytes, monocytes, and activated T cells and B cells. We found that murine DC express in vitro as well as in vivo both major isoforms of CEACAM1, CEACAM1-L (having a long cytoplasmic domain with immunoreceptor tyrosine-based inhibitory motifs) and CEACAM1-S (having a short cytoplasmic domain lacking phosphorylatable tyrosine residues). Ligation of surface-expressed CEACAM1 on DC with the specific mAb AgB10 triggered release of the chemokines macrophage inflammatory protein 1alpha, macrophage inflammatory protein 2, and monocyte chemoattractant protein 1 and induced migration of granulocytes, monocytes, T cells, and immature DC. Furthermore, the surface expression of the costimulatory molecules CD40, CD54, CD80, and CD86 was increased, indicating that CEACAM1-induced signaling regulates early maturation and activation of dendritic cells. In addition, signaling via CEACAM1 induced release of the cytokines IL-6, IL-12 p40, and IL-12 p70 and facilitated priming of naive MHC II-restricted CD4(+) T cells with a Th1-like effector phenotype. Hence, our results show that CEACAM1 is a signal-transducing receptor that can regulate early maturation and activation of DC, thereby facilitating priming and polarization of T cell responses.

Inhibition of nonopsonic Helicobacter pylori-induced activation of human neutrophils by sialylated oligosaccharides

Certain strains of Helicobacter pylori have nonopsonic neutrophil-activating capacity. Some H. pylori strains and the neutrophil-activating protein of H.pylori (HPNAP) bind selectively to gangliosides of human neutrophils. To determine if there is a relationship between the neutrophil-activating capacity and the ganglioside-binding ability, a number of H. pylori strains, and HPNAP, were incubated with oligosaccharides, and the effects on the oxidative burst of subsequently challenged neutrophils was measured by chemiluminescence and flow cytometry. Both by chemiluminescence and flow cytometry a reduced response was obtained by incubation of H.pylori with sialic acid-terminated oligosaccharides, whereas lactose had no effect. The reductions obtained with different sialylated oligosaccharides varied to some extent between the H. pylori strains, but in general 3'-sialyllactosamine was the most efficient inhibitor. Challenge of neutrophils with HPNAP gave no response in the chemiluminescence assay, and a delayed moderate response with flow cytometry. Preincubation of the protein with 3'-sialyllactosamine gave a slight reduction of the response, while 3'-sialyllactose had no effect. The current results suggest that the nonopsonic H. pylori-induced activation of neutrophils occurs by lectinophagocytosis, the recognition of sialylated glycoconjugates on the neutrophil cell surface by a bacterial adhesin leads to phagocytosis and an oxidative burst with the production of reactive oxygen metabolites.

Biliary glycoprotein 1 expression during embryogenesis: correlation with events of epithelial differentiation, mesenchymal-epithelial interactions, absorption, and myogenesis

Biliary glycoprotein (Bgp1), a carcinoembryonic antigen-related family member of the immunoglobulin superfamily, is involved in normal and neoplastic events. Analysis of Bgp1 expression throughout post-implantation mouse embryogenesis using reverse transcription-polymerase chain reactions, immunostaining with anti-Bgp1 monoclonal antibodies, and in situ hybridization with specific Bgp1 cDNA fragments revealed that Bgp1 may be involved in a number of specific embryonic processes. Immunoblot analysis of Bgp1 deletion mutant proteins indicated that distinguishable epitopes of the molecule were preferentially identified by the three Bgp1 antibodies used in this study. This distinction is supported by our immunolocalization studies during mouse embryogenesis in which the three antibodies revealed specific patterns of Bgp1 expression. Bgp1 is not expressed in early post-implantation embryos (7.5 dpc), but is found in the placenta and extra-embryonic tissues (decidual endothelial cells, giant trophoblasts, yolk sac visceral endoderm, and endometrial glands) at this time. The primitive gut epithelium and surface ectoderm were the first embryonic tissues to express Bgp1. Significant Bgp1 expression was also observed later during epithelial-mesenchymal interactions (skin, meninges, lung, kidney, salivary glands, pancreas). A unique epitope of Bgp1, detectable by the monoclonal antibody CC1, was also associated with mesenchymal expression and was prominent during myogenesis (secondary myotube formation) at sites of terminal differentiation. These studies suggest multiple roles for isoforms and glycoforms of the Bgp1 proteins localized in specific sites during prenatal development.

D11, a novel monoclonal antibody specific for human mature macrophages and peripheral blood monocytes

A new monoclonal antibody designated Mab D11 is described, which shows a restricted reactivity to cells of the monocyte/macrophage system. When tested by light and electron microscopic immunoperoxidase methods, Mab D11 specifically reacts with blood monocytes and stains resident macrophages in a wide variety of human tissues; it does not mark the macrophages of other species, i.e., rat, swine and mouse. Antigen-presenting cells, e.g., Langerhans cells, are Mab D11 negative. Mab D11 reveals the antigen on cryostat and paraffin tissue sections. Ultrastructurally the antigen recognized by Mab D11 in all macrophage types studied is located on the plasma membrane and within cytoplasmic structures including lysosomes. On immunoblotting, Mab D11 detects the 125-kDa antigen in human liver and the 135-kDa protein in tumours of histiocytic origin. The similarity of Mab D11 to known "pan-macrophage" monoclonal antibodies is discussed.

Conformational effects of volatile anesthetics on the membrane-bound acetylcholine receptor protein: facilitation of the agonist-induced affinity conversion

The rate of the carbamylcholine-induced affinity conversion of the membrane-bound acetylcholine receptor protein from Torpedo californica is enhanced by pretreatment of the membranes under an atmosphere of 3% halothane or 1% chloroform. The enhancement is much more pronounced in the presence of low rather than high concentrations of carbamylcholine since the volatile anesthetics alter the apparent dissociation constant for carbamylcholine from 17 to 3 microM without affecting the first-order rate constant for the ligand-induced conversion (0.07 s-1). These results indicate that the acetylcholine receptor is assuming a conformational form with intermediate affinity for carbamylcholine in addition to the previously described low- and high-affinity forms. The dissociation constants for carbamylcholine obtained from kinetic studies of the carbamylcholine-induced transition are 3-15-fold lower than those obtained as inhibition constants from the rate of 125I-labeled alpha-bungarotoxin binding to the low-affinity conformer of the acetylcholine receptor protein. This pattern, observed in both the presence and absence of anesthetic, provides further evidence that the acetylcholine receptor has nonequivalent ligand binding sites for carbamylcholine.