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Helicobacter pylori NCTC 11637 produces a water‐insoluble biofilm when grown under defined conditions with a high carbon:nitrogen ratio in continuous culture and in 10% strength Brucella broth supplemented with 3 g l−1 glucose. Biofilm accumulated at the air/liquid interface of the culture. Light microscopy of frozen sections of the biofilm material showed few bacterial cells in the mass of the biofilm. The material stained with periodic acid Schiff’s reagent. Fucose, glucose, galactose, and glycero‐manno‐heptose, N‐acetylglucosamine and N‐acetylmuramic acid were identified in partially purified and in crude material, using gas chromatography and mass spectrometry. The sugar composition strongly indicates the presence of a polysaccharide as a component of the biofilm material. Antibodies (IgG) to partially purified material were found in both sero‐positive and sero‐negative individuals. Treatment of the biofilm material with periodic acid reduced or abolished immunoreactivity. Treatment with 5 mol l−1 urea at 100 °C and with phenol did not remove antigenic recognition by patient sera. The production of a water‐insoluble biofilm by H. pylori may be important in enhancing resistance to host defence factors and antibiotics, and in microenvironmental pH homeostasis facilitating the growth and survival of H. pylori in vivo.

of the monolayer. Intestinal epithelial cells can be defined as playing an important role in both innate and adaptive immune responses. This review attempts to outline some of the mechanisms by which IECs participate in both these forms of defense. Role of IECs in innate mucosal immunityThe intestinal lumen, particularly that of the colon, contains a large variety of bacteria and bacterially derived products. 1,2 A number of "broadly-specific" defense mechanisms have evolved to guard against the risk of attack from invasive microorganisms. These mechanisms can be classified as intrinsic or extrinsic in nature. Intrinsic mechanisms of immunity are derived from the physical presence of an epithelial barrier and are dependent upon the unique structural properties exhibited by the IEC. Extrinsic defenses are defined as those processes which act outside the monolayer to resist microbial interaction with the mucosa. Intrinsic immunity: barrier functionThe formation of a selectively permeable epithelial barrier is essential in preventing the uncontrolled passage of pathogenic antigens from the external environment to the internal tissue. Establishment of the epithelial monolayer by contributing IECs is dependent upon a considerably high degree of intracellular and intercellular organization (for a review, see 3 ). Within each epithelial cell, structural integrity is maintained by the presence of a complex cytoskeletal network of microfilaments. These filaments vary in their composition and location. Actin-based filaments, for example, form rings at both the apical and basolateral poles of the cell, while intermediate filaments course through the cytoplasm and anchor at points of the plasma membrane. 4,5 Together, these structures are crucial in maintaining cellular polarity and in supporting points of cell-cell contact.

The B subunit of Escherichia coli heat‐labile enterotoxin (EtxB) is a potent immunomodulatory molecule capable of treating and preventing autoimmune disease. These properties result from its ability to bind to glycolipid receptors, principally GM1 ganglioside, and modulate immune cell function. EtxB receptor binding causes B cell activation, modulates monocyte cytokine secretion and triggers apoptosis of CD8+ T cells. These wide‐ranging effects suggest that B subunit receptor interaction triggers signaling events affecting cellular differentiation. We have investigated the processes by which EtxB induces CD8+ T cell apoptosis. We show that receptor interaction by EtxB activates caspase‐3 in CD8+ but not in CD4+ T cells. Inhibition of caspase‐3 blocks the apoptotic process. EtxB induces the activation of NF‐κB in both CD8+ and CD4+ T cells. The findings that (i) SN50, a peptide inhibitor of NF‐κB nuclear translocation, prevents caspase‐3 activation and subsequent apoptosis, and (ii) CD8+CD4– thymocytes from transgenic mice expressing a dominant‐negative form of the IκBα protein were markedly less susceptible to EtxB‐induced apoptosis than cells from wild‐type mice, indicate that NF‐κB is important in the induction of the apoptotic pathway. Further investigations revealed that while caspase‐8 activity is detected concomitant to caspase‐3, caspase‐9 activation, following mitochondrial cytochrome c release, is detectable later on. These observations are consistent with death receptor‐mediated signaling, however, experiments using lpr/lpr and p55 TNFR –/– mice rule out the involvement of Fas and the p55 TNF receptor, respectively. The data therefore indicate that EtxB‐mediated apoptosis occurs via a novel pathway involving NF‐κB.

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CD1d is expressed on the surface of professional and nonprofessional APCs, including intestinal epithelial cells (IECs), for a role in the presentation of glycolipid-based antigens to subsets of T cells. The mechanisms that regulate CD1d expression in any cell type are unknown. To investigate the possibility that expression of CD1d is influenced by exogenous factors present within the intestinal lumen, CD1d expression was analyzed in several IEC lines after culturing in the presence of lumenal contents (LC) of the normal human intestine. Exposure of the colon-derived cell lines T84, HT-29, and Caco-2 to soluble LC resulted in a marked induction of CD1d expression as determined by RT-PCR, confocal microscopy, cell surface ELISA, and Western blot analysis. Similarly, exposure of human IECs to LC isolated from mice bred in both specific pathogen–free and germfree conditions also resulted in the induction of CD1d expression, with the maximum CD1d-inducing activity observed in the small intestine. Biochemical and biophysical characterization of the human CD1d-inducing activity identified heat shock protein 110 (Hsp110) as a major functional component of the LC that contributes to CD1d surface regulation, and immunolocalization studies revealed Hsp110 expression in subsets of human IECs in vivo. These data support the presence of a novel autocrine pathway of CD1d regulation by Hsp110

The human major histocompatibility complex (MHC) on chromosome 6 encodes three classical class-I genes: human leukocyte antigens (HLA) A, B, and C. These polymorphic genes encode a 43-to 45-kDa cell surface glycoprotein that, in association with the 12-kDa β 2 -microglobulin molecule, functions in the presentation of nine amino acid peptides to the T-cell receptor of CD8-bearing T lymphocytes and killer inhibitory receptors on natural killer cells. In addition to these ubiquitously expressed, polymorphic proteins, the human genome also encodes several nonclassical MHC class-I-like, or class Ib, genes that, in general, encode nonpolymorphic molecules involved in various specific immunological functions. Many of these genes, including CD1, the neonatal Fc receptor for IgG, HLA-G, HLA-E, the MHC class-I chain-related gene A, and Hfe, are prominently displayed on epithelial cells, suggesting an important role in epithelial cell biology. KeywordsEpithelium; intestine; major histocompatibility complex It is increasingly recognized that epithelial cells, especially intestinal epithelial cells (IEC), play an important role in innate and adaptive immune functions in addition to their important barrier, absorption, and transport functions (1). A structural form that is particularly useful to the epithelial cells in fulfilling these immunological functions is that provided by the major histocompatibility complex (MHC) class-I-related molecules. By understanding the composition of these molecules, insight can be provided into possible functions of these molecules in epithelial cells. Classical MHC class I moleculesThe basic structure of the MHC class-I-related molecules reflects that encoded by the classical MHC class-I or class Ia genes (2,3). These genes are encoded within the MHC class-I locus on human chromosome 6 and consist of the human leukocyte antigens (HLA) A, B, and C.Publisher's Disclaimer: Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. The open reading frame of these genes consists of structural domains encoded by discrete exons that translate into an approximately 43-to 45-kDa glycoprotein containing three membrane distal domains (α1, α2, and α3), a transmembrane domain, and a cytoplasmic tail. The most membrane-proximal ec...

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