Epithelial HLA-DR expression and lymphocyte subsets in gastric mucosa in type B chronic gastritis

Helicobacter pylori-induced interleukin-12 p40 expression

Interleukin-12 (IL-12) is a heterodimeric cytokine produced by antigen-presenting cells that promotes the development of T-helper lymphocyte 1 (Th1). Chronic gastritis induced by Helicobacter pylori is considered a Th1-mediated process. IL-12 levels in gastric biopsy samples of H. pylori-infected patients are higher than in those of uninfected individuals, but the cellular source of IL-12 remains elusive. IL-12 staining was detected in mucosal epithelial cells, lymphocytes, and macrophages in specimens of patients with H. pylori-positive gastritis. Therefore, we investigated IL-12 p40 mRNA induction by H. pylori in gastric epithelial cells and T cells. Although cag pathogenicity island (PAI)-positive H. pylori induced IL-12 p40 mRNA expression, an isogenic mutant of the cag PAI failed to induce it in both cell types. Supernatants from H. pylori cultures and H. pylori VacA induced IL-12 p40 mRNA expression in T cells but not in epithelial cells. The activation of the IL-12 p40 promoter by H. pylori was mediated through NF-kappaB. The transfection of IkappaB kinase and NF-kappaB-inducing kinase dominant-negative mutants inhibited H. pylori-induced IL-12 p40 activation. Inhibitors of NF-kappaB, phosphatidylinositol 3-kinase, p38 mitogen-activated protein kinase, and Hsp90 suppressed H. pylori- and VacA-induced IL-12 p40 mRNA expression. The results indicate that H. pylori induces IL-12 p40 expression by the activation of NF-kappaB, phosphatidylinositol 3-kinase, and p38 mitogen-activated protein kinase. Hsp90 is also a crucial regulator of H. pylori-induced IL-12 p40 expression. In addition to the cag PAI, VacA might be relevant in the induction of IL-12 expression and a Th1-polarized response only in T cells.

Conventional, regulatory, and unconventional T cells in the immunologic response to Helicobacter pylori

Infection by the gastroduodenal pathogen Helicobacter pylori elicits a complex immunologic response in the mucosa involving neutrophils, plasma cells, eosinophils, and lymphocytes, of which T cells are the principal orchestrators of immunity. While so-called classical T cells (e.g. T-helper cells) that are activated by peptide fragments presented on antigen-presenting cells have received much attention in H. pylori infection, there exists a diverse array of other T cell populations that are potentially important for the outcome of the ensuing immune response, some of which have not been extensively studied in H. pylori infection. Pathogen-specific regulatory T cells that control and prevent the development of immunopathology associated with H. pylori infection have been investigated, but these cells can also benefit the bacterium in helping to prolong the chronicity of the infection by suppressing protective immune responses. An overlooked T cell population, the more recently described Th17 cells, may play a role in H. pylori-induced inflammation, due to triggering responses that ultimately lead to the recruitment of polymorphs, including neutrophils. The so-called innate or unconventional T cells, that include two conserved T cell subsets expressing invariant antigen-specific receptors, the CD1d-restricted natural killer T cells which are activated by glycolipids, and the mucosal-associated invariant T cells which play a role in defense against orally acquired pathogens in the intestinal mucosa, have only begun to receive attention. A greater knowledge of the range of T cell responses induced by H. pylori is required for a deeper understanding of the pathogenesis of this bacterium and its ability to perpetuate chronic infection, and could reveal new strategies for therapeutic exploitation.

Mucosal lymphocyte subsets and HLA-DR antigen expression in paediatric Helicobacter pylori-associated gastritis

Paediatric studies may provide important insights into the immunopathology of Helicobacter pylori-associated gastritis, as mucosal changes reflect different stages of the immunoinflammatory response. We characterized, by quantitative immunohistochemistry, gastric mucosal lymphocyte phenotype and HLA-DR antigen expression and evaluated correlation with histopathology, in H. pylori-infected (Hp+ve) and uninfected children (Hp-ve). In the infected group, lamina propria CD3+ and IgA plasmocyte cell numbers were significantly higher and a trend for predominance of CD8+ over CD4+ was observed both in epithelium and lamina propria. A correlation of inflammation score with lamina propria CD3+ and CD4+ cell numbers and of CD45RO+ T lymphocytes with density of colonization was observed. The proportion of epithelial cells expressing HLA-DR antigen was significantly higher in the Hp+ve group and furthermore, glandular HLA-DR expression correlated with lamina propria CD3+ cell numbers, emphasizing the potential role of epithelial cells as antigen-presenting cells at this stage of infection.

Increase of antigen-presenting cells in the gastric mucosa of Helicobacter pylori-infected children

BACKGROUND

Infection with Helicobacter pylori leads to an increase of T cells in the gastric mucosa of children. In contrast to peripheral blood, where monocytes are the most abundant antigen-presenting cells, CD14+ macrophages are very rare in infected gastric mucosa. We postulated that other types of antigen-presenting cells must be present in infected gastric mucosa.

MATERIAL AND METHODS

Antral biopsies were obtained from 56 children. The cellular expression of major histocompatibility complex (MHC) class II molecules, CD1a/b, and CD23, which are involved in antigen presentation were analyzed by immunohistochemistry. In addition, T cells (CD4, CD8, CD25, and gamma/delta-TCR), B cells (anti-IgM), macrophages (CD14) and granulocytes (CD15) were quantified.

RESULTS

Twenty-eight children were H. pylori-infected. Thirteen children were healthy, 15 had other gastric pathologies. T cells (p<.0001), B cells (p<.0001), CD23+ (p<.0001), and CD1a/b+ (p<.005) cells were significantly increased in the lamina propria of H. pylori-infected children, whereas macrophages were rare without significant differences among the groups. Within the epithelium, CD8+ T lymphocytes predominated clearly over CD4+ cells. H. pylori-negative children had only few MHC class II-positive cells within the gastric epithelium, whereas MHC class II antigens were strongly expressed on epithelial cells (p<.0001) of all H. pylori-infected children.

CONCLUSION

Helicobacter pylori infection leads to an enhanced expression of antigen-presenting molecules together with a parallel rise of T cells in the lamina propria. This may represent an effort of the immune system to optimize local immune responses against H. pylori. We speculate that the epithelium participates in the initiation of a local immune response against H. pylori.

Th response to Helicobacter pylori differs between patients with gastric ulcer and duodenal ulcer

OBJECTIVE

Helicobacter pylori (H. pylori) infection induces both gastric (GU) and duodenal ulcers (DU). We examined whether host immunological response to H. pylori determines different disease outcomes.

MATERIAL AND METHODS

Thirty-two GU and 28 DU patients infected with H. pylori, and 24 dyspeptic patients without infection were enrolled. The constituents of cellular infiltrates in biopsies from each patient were determined and lymphokines secreted by stimulated T cells were measured. Serum concentrations of IgG subclasses specific to H. pylori were measured.

RESULTS

Low pepsinogen I and high pepsinogen II levels were observed in GU patients, while a high pepsinogen I level was found in DU patients. T cells predominate over other cell types in both GU and DU patients. GU patients had a higher number of T cells (p < 0.01) and lower plasma cells (p < 0.05) than those in DU patients. T cells from GU patients produced greater amounts of IFN-gamma and less IL-4 than those in DU patients (p < 0.01). GU patients had a higher serum level of IgG2 specific to H. pylori than that in DU patients (p < 0.01).

CONCLUSIONS

Th response by gastric T cells in GU patient was more polarized to Th1 as compared with that in DU patients, suggesting that a distinct immune response to H. pylori induces different disease outcomes.

Expression of HLA-DR, costimulatory molecules B7-1, B7-2, intercellular adhesion molecule-1 (ICAM-1) and Fas ligand (FasL) on gastric epithelial cells in Helicobacter pylori gastritis; influence of H. pylori eradication

There is evidence that Helicobacter pylori infection up-regulates the expression of HLA class II molecules by gastric epithelial cells (GEC). In this study we evaluated whether GEC are capable of expression of costimulatory molecules in H. pylori gastritis. The expression of FasL by GEC, before and after eradication of H. pylori, was also studied. Thirty patients (23 men) aged 27-81 years (53.67 +/- 13.99 years (mean +/- s.d.)) with dyspepsia were studied. Upper gastrointestinal endoscopy was performed and six biopsies were obtained (antrum, n = 3; corpus, n = 3) for Campylobacter-Like Organisms (CLO) test and histology; 23 (16 men) were H. pylori+ and seven (all men) were H. pylori- by both methods and served as controls. Helicobacter pylori eradication therapy was given to H. pylori+ patients and all patients were re-endoscoped after 116 +/- 9 days. Formalin-fixed paraffin-embedded tissue sections were stained by the ABC immunoalkaline phosphatase method. In H. pylori gastritis HLA-DR was expressed and correlated with disease activity (P < 0.01). No HLA-DR was observed in controls. In H. pylori-eradicated patients significant decrease of HLA-DR was found (antrum, P < 0. 001). ICAM-1 was expressed by GEC in 80% of H. pylori+ patients; ICAM-1 expression did not correlate with gastritis parameters and decreased significantly after eradication (antrum, P < 0.01). B7-1 and B7-2 were expressed on H. pylori+ samples and their expression decreased after eradication, albeit not significantly. Weak epithelial expression of both B7 molecules was observed in all the controls. FasL was steadily expressed by GEC in both H. pylori+ and H. pylori- patients and remained almost unchanged after eradication. These findings suggest that GEC may acquire antigen-presenting cell properties in H. pylori infection through de novo expression of HLA-DR and costimulatory molecules. This seems to be attenuated after eradication and resolution of mucosal inflammation. The same cells exhibit the capacity to control the inflammatory process, probably by inducing apoptotic cell death to Fas-bearing infiltrating lymphocytes.

The inflammatory response in CD1 mice shortly after infection with a CagA+/VacA+ Helicobacter pylori strain

To investigate the early events of Helicobacter pylori infection in a mouse model, CD1 mice were infected with a type I (CagA+/VacA+) H. pylori strain. Up to 4 weeks after infection the majority of gastric tissue biopsies were positive in culture. Immunohistochemical analysis showed that inflammatory changes started to occur after 3 weeks. Four weeks after infection a significant increase in T cells was observed in the cardia/corpus region of the stomachs of infected mice. These T cells were CD4+ and CD8+, and they were located in an area with increased expression of MHC class II antigens. In 50% of the infected mice also an increased number of mast cells was seen. Furthermore, aggregates of B and T cells were present in the submucosa. Characterization of cytokines by immunohistochemistry showed an increase in IL-5-secreting cells in the inflamed area of the infected stomach. No difference was observed between interferon-gamma (IFN-gamma)-, IL-4- and IL-10-secreting cells in control and infected mice. These results suggest that no polarized T-helper cell response was present at this early phase of infection. Infection with H. pylori also induced a serum response and especially IgG was increased after 4 weeks of infection. However, no particular increase in IgG1, IgG2a or IgG3 isotype was observed. Part of the serum antibodies was directed against lipopolysaccharide (LPS), but no evidence for anti-Lewis antibodies or antibodies against epitopes on the gastric mucosa was found.

Antrum- and corpus mucosa-infiltrating CD4(+) lymphocytes in Helicobacter pylori gastritis display a Th1 phenotype

In this study, cytokine patterns produced by CD4(+) T cells isolated from antrum or corpus gastral biopsy specimens of 10 patients with Helicobacter pylori-positive gastritis were compared. To this end, expression of intracellular cytokines (interleukin-4 [IL-4] and gamma interferon) and of CD4 was assessed by flow cytometry. Ten to 60% of the isolated CD4(+) T cells produced gamma interferon upon stimulation. With the exception of one patient, IL-4-positive CD4(+) cells were not detected. Therefore, CD4(+) cells infiltrating antrum and corpus stomach mucosa during H. pylori infection show a Th1 phenotype. This polarized Th1-type response may contribute to the inability of the immune system to eradicate H. pylori infection.

Characterization of lymphocytic subsets and cytokine production in gastric biopsy samples from Helicobacter pylori patients

BACKGROUND

This study characterized the phenotypic subsets of isolated gastric lymphocytes and the cellular immune response in cultured gastric biopsy specimens.

METHODS

Endoscopy specimens from 40 Helicobacter pylori-positive and 40 H. pylori-negative patients were studied. a) Isolated gastric lymphocytes were analysed for CD4+, CD8+ T-lymphocyte subsets, activated T cells, and natural killer cells on a fluorescence-activated cell sorter, using monoclonal antibodies. b) The supernatant of cultured gastric biopsy specimens were assayed for interleukin (IL)-2, IL-4, and IL-6 levels.

RESULTS

In H. pylori-positive patients there was (a) a decrease in CD4+/CD8+ T cells, no change in activated T cells, and an increase in natural killer cells, and (b) no change in IL-2 levels and a significant increase in IL-4 and IL-6 levels.

CONCLUSIONS

There is an increase in CD8+ lymphocytes and natural killer cells, and the observed increase in IL-4 and IL-6 might be important in H. pylori-associated gastritis.

Hypotheses on the role of cytokines in peptic ulcer disease

Helicobacter pylori is the cause of chronic type B gastritis and occurs in almost all patients with duodenal ulcers. Infection with H. pylori is characterized by an increased production of several inflammatory cytokines. Increasing evidence suggests a central role of these cytokines in the pathogenesis of H. pylori-associated gastritis and peptic ulcer disease. Cytokines may be crucial in the recruitment and activation of inflammatory cells and in stimulation of gastrin release. In addition to their proinflammatory properties, cytokines may also inhibit the ulcer occurrence by stimulation of prostaglandins and somatostatin release and by direct impairment of acid secretion. The balance of these factors may determine the clinical outcome of H. pylori infection.

A study of accessory cells in the acquired lymphoid tissue of helicobacter gastritis

This paper presents a description of the patterns of distribution of accessory cells in helicobacter gastritis and low-grade gastric MALT lymphomas. The use of gastric resection specimens afforded abundant, well-orientated lymphoid tissue. Fifteen cases were selected from patients with MALT lymphomas, three with gastritis alone, and six histologically normal controls. A panel of antibodies working in paraffin-embedded tissue, identifying differing accessory cells, was used. These comprised antibodies to HLA class II (WR18), acid cysteine proteinase inhibitor (ACPI), CD68 (PGM1), Factor XIIIa, S100 protein, CD23 (BU38), CD106 (V-CAM1), CD55 (BRIC 128), and CD21 (1F8). CD68-positive macrophages in the gastritis cases were abundant in the superficial mucosa. Factor XIIIa also identified dendritic cells at deeper sites but these were absent from both the acquired and the neoplastic lymphoid tissue. Antibodies to both S100 protein and ACPI stained dendritic cells localized to areas within and adjacent to the lymphoid tissue only. S100 protein-positive cells were concentrated in close contact with glandular epithelium immediately above the germinal centres, while ACPI-positive dendritic cells were identified, especially around the more blastic reactive follicles, in the intervening space between the germinal centres and the overlying epithelium. Similar patterns of organization were also seen in the areas of mucosal lymphoma. The follicular dendritic markers revealed overlapping but distinct sub-populations within the germinal centres which appeared to alter depending on the activity of the germinal centres. While both ACPI and CD55 stained the germinal centre dendritic reticulum cell networks only, CD21 and CD106 also stained the mantle dendritic cells. The proportion staining with CD23, which stains dendritic reticulum cells within the centrocyte-rich areas of the germinal centres only, was greatest in the more quiescent germinal centres. Similar patterns of staining were also seen in germinal centres within the gastric MALT lymphomas. It is proposed that the sub-populations of dendritic cells staining with S100 protein and ACPI may facilitate helicobacter antigen delivery to the germinal centres. The follicular dendritic cells then promote a sustained B-cell response to the luminal pathogen.

Manifestations of the local gastric immune response in gnotobiotic piglets infected with Helicobacter pylori

Helicobacter pylori, a human gastric bacterial pathogen, was inoculated into gnotobiotic piglets and manifestations of the resultant gastric inflammation was analyzed by in situ immunochemistry and flow cytometric analysis of isolated lamina propria leukocytes (LPL) and peripheral blood leukocytes (PBL) recovered from infected and control piglets. Gastric mucosa tissue sections from uninfected control piglets were essentially negative for cluster differentiation- (CD-) positive leukocytes. Failure to isolate significant numbers of LPL from the gastric lamina propria confirmed this observation. A local and systemic immune response occurs in piglets after infection with H. pylori. This is manifest by the appearance of cells associated with a local immune response in gastric mucosa. In gastric tissue sections from H. pylori-infected piglets, CD4-positive leukocytes were sparse and closely associated with developing lymphoid follicles whereas the CD8-positive cellular phenotype was abundant. The latter formed a continuous band in the lamina propria just above the muscularis mucosa. Perivascular accumulations of lymphocytes in the outer muscular tunic(s) were strongly positive for expression of CD8 antigen. Class II-positive cells were prominent in CD8 lymphocytic infiltrates, developing follicles and vascular endothelia but were uniformly absent from gastric epithelia even in sites overlying areas of immunocyte proliferation and infiltration. Leukocytes possessing the monocyte and granulocyte markers were rare. Plasma cells containing IgA were common in the periphery of developing lymphoid follicles or distributed as discrete foci around individual gastric pits. Fewer numbers of IgG- and IgM-positive plasma cells were identified. When the LPL flow cytometry data were compared with the flow cytometry data obtained from PBL in these same H. pylori-infected piglets, leukocytes bearing the CD8 marker predominated in LPL whereas leukocytes bearing the CD4-reactive and MHC class II markers predominated in PBL. Finally, local ELISA antibody responses were measured in mucosal explant culture supernatants and compared with in vivo antibody levels in sera, bile, and gastric juice. Antibody activity, specific for H. pylori, was detected in supermatants and serum in all three isotypes in actively infected piglets whereas gastric juice lacked antibodies. Gastric explants prepared from piglets in which infection had been successfully eradicated failed to produce local antibody into supermatant fluids. These data support the concept that the gastric inflammation observed is mediated by local immunological events.

Characterization of lymphocytic infiltrates in Helicobacter pylori-associated gastritis

BACKGROUND

This study evaluated the specific subset composition of lymphocytes present in Helicobacter pylori-associated gastritis (HAG), since reports so far have led to inconclusive and conflicting results.

METHODS

Endoscopic biopsy specimens from 56 patients were studied by quantitative immunohistochemistry using monoclonal antibodies against the lymphocyte markers CD3, CD22, CD4, CD8, CD45RO, CD1O3, TCR alpha/beta, and TCR gamma/delta. Lamina propria and intraepithelial compartments were evaluated separately. Grade, activity, and density of bacterial colonisation were assessed histologically and with Warthin-Starry stain.

RESULTS

Evaluation showed a significant increase in CD4+, CD45RO+, TCR alpha/beta+ activated lamina propria lymphocytes in HAG which correlated with grade and activity of gastritis and degree of bacterial colonisation, whereas subsets of intraepithelial lymphocytes did not change significantly. TCR gamma/delta+ T cells were not found to be increased in HAG.

CONCLUSIONS

Selective expansion of CD4+, CD45RO+ memory-type T cells could reflect an antigen-specific and/or chemokine-mediated effect in HAG. Locally produced CC chemokines such as RANTES have been detected in HAG.

Expression of cytokine mRNA in gastric mucosa with Helicobacter pylori infection

BACKGROUND

We have studied the cytokine production patterns in gastric mucosal biopsy specimens with and without the Helicobacter pylori infection, using a reverse transcription-polymerase chain reaction (RT-PCR) method capable of detecting low levels of specific mRNA.

METHODS

Total RNA was prepared from biopsy specimens with the acid guanidinium thiocyanate-phenol-chloroform method. cDNA was synthesized by M-MLV RTase and amplified using the oligonucleotide primers specific for interleukin-1 beta (IL-1beta), IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, tumor necrosis factor-alpha (TNF-alpha), interferon-alpha (IFN-alpha), IFN-beta, and IFN-gamma by PCR methods.

RESULTS

Although IL-1 beta and IFN-gamma mRNA were detected in most specimens, IL-2, IL-3, IL-4, IL-5, IL-9, TNF-alpha, and IFN-beta mRNA were not detected at all. The expressions of IL-7 and IL-8 mRNA were significantly higher in H. pylori-positive gastritis than in H. pylori-negative normal controls. There was a significant correlation between the expression of IL-8 mRNA and the severity of gastritis both in the antrum and in the corpus. On the other hand, there was a significant correlation between the expression of IL-7 mRNA and the severity of gastritis only in the corpus.

CONCLUSIONS

These findings suggest that some cytokines, especially IL-7 and IL-8, play some roles in H. pylori-associated gastritis.

Topographic study of Helicobacter pylori and HLA-DR antigen expression on gastric epithelium

Helicobacter pylori and HLA-DR antigen expression on gastric epithelium, identified by an indirect immunoperoxidase staining method using monoclonal antibodies against H. pylori and HLA-DR antigens, were studied topographically. Fifty-nine biopsy specimens from 41 patients who had neither gastric cancer nor peptic ulcers were examined. H. pylori was observed predominantly over or on the surface epithelium, while HLA-DR antigens were frequently expressed on the epithelium of the isthmus region. These observations led to the conclusion that there was no direct topographic association between H. pylori and epithelial HLA-DR expression. However, the frequency of HLA-DR expression in H. pylori-positive (28/29) specimens was significantly higher than that in H. pylori-negative (18/30) specimens (P < 0.01). Furthermore, a greater number of H. pylori was associated with a stronger expression of HLA-DR antigens (P < 0.001). We conclude that H. pylori is indirectly related to HLA-DR expression on gastric epithelium. H. pylori is the first microbial agent that has been suggested to be associated with epithelial HLA-DR expression in the human gastrointestinal tract.

Mucosal tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-8 production in patients with Helicobacter pylori infection

We investigated whether tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and interleukin-8 (IL-8) are involved in the inflammatory reaction of Helicobacter pylori infection. In 23 patients with H. pylori infection and 16 patients with negative cultures for H. pylori and normal antral mucosa, the mucosal production of TNF-alpha, IL-1 beta, and IL-8 was measured in antral biopsy specimens after 23 h of in vitro culture. The levels of TNF-alpha and IL-1 beta appeared to be significantly higher in H. pylori-positive patients (p = 0.0002 for both TNF-alpha and IL-1 beta). IL-8 production was also higher in H. pylori-infected subjects, but this difference did not reach statistical significance (p = 0.057). No significant differences were found between the level of the cytokines in H. pylori-infected patients with or without duodenal ulcer disease. A strong correlation was found between the production of IL-1 beta and IL-8. The biologic effects of these cytokines may explain the conspicuous recruitment, influx, and activation of neutrophils in the gastric mucosa during H. pylori infection.

Expression of HLA-class II antigen in gastric carcinomas. Its relationship to histopathological grade, lymphocyte infiltration and five-year survival rate

To investigate whether the expression of HLA-DR antigen in gastric carcinomas is associated with the survival rate, we studied 70 cases of gastric carcinoma using a monoclonal antibody. Forty-seven cases (67%) stained positively, including 31 differentiated carcinomas, and 16 undifferentiated carcinomas. A close correlation was found between expression of HLA-DR antigen and differentiation of the tumor cells. Marked lymphocyte infiltration was seen in the HLA-DR antigen positive cancers. In advanced gastric cancers, the 5-year survival rate of patients with HLA-DR antigen positive cancers was significantly higher (67.5%) than that of patients with HLA-DR antigen negative cancers (40%). The data suggest that the expression of HLA-DR antigen in gastric carcinomas may reflect the degree of tumor cell differentiation, and influence the host immune response and prognosis.

The role of Helicobacter pylori in acid-peptic disease

Acid peptic disease is common, and its management is costly. Less than a decade ago, the traditional theories regarding the etiology and pathogenesis of acid peptic disease were upset by the discovery of Helicobacter pylori infection in association with chronic active gastritis. A substantial body of investigation after that discovery has established this infection as the major cause of human chronic active gastritis and has defined a critical role for H. pylori in the etiology, pathophysiology, and treatment of duodenal ulcer disease. Furthermore, evidence is accumulating to link H. pylori to gastric ulcers, non-ulcer dyspepsia, and even gastric carcinoma. Research has clarified some unique features of the organism that have been put to advantage in the development of diagnostic tests, and it has also clarified some features of the infection that make it difficult to treat. Although treatment is decidedly beneficial for certain patient subsets, simpler and more effective therapy is needed.

Langerhans cells and lymphocyte subsets in human gastrointestinal carcinomas. An immunohistological study on frozen sections

In an immunohistochemical study of 38 human gastric and 40 human colonic carcinomas Langerhans cells, suppressor and helper lymphocytes were identified on frozen sections by using anti-CD1, anti-CD8 and anti-CD4 monoclonal antibodies. Tumours were divided into those with few (< 3 per high power field) and those with many (> 3 per high power field) Langerhans cells as well as into those with high number of CD4 and CD8 cells (> 30 per high power field). No significant difference in the number of Langerhans cells regarding histologic types, degree of differentiation and metastatic/non-metastatic groups of either gastric or colonic carcinomas was found. On the contrary the numbers of Langerhans cells related significantly (p < 0.05) to density of T-cell and especially CD4 cell infiltrations of gastric and colonic carcinomas. This finding supports the role of Langerhans cells as antigen presenting cells and their involvement in T-cell activation against neoplastic cells of human gastrointestinal carcinomas.

Intestinal intraepithelial lymphocytes and lymphoepithelial interactions in the human gastrointestinal mucosa

Although representing a major immunological apparatus, it is not known how the immune system of the intestinal mucosa differentiates between dietary antigens (resulting in systemic tolerance) and potential pathogens. It is thought that intraepithelial T lymphocytes (IEL) may play a central role in local intestinal immunity and are likely to be important in immunity to gastrointestinal neoplasms and rejection responses to gut allografts. However, the biology of IEL and their unusual immunological microenvironments in the gastrointestinal mucosa are little understood. IEL are predominantly CD8+ TcR alpha beta+ CD3+ T cells which differ from lamina propria and peripheral T cells in many respects. IEL show low expression of CD5, CD6, LFA-1 (CD11a/CD18) and VLA-4, and high expression of HML-1. TcR gamma delta + IEL, although a minority population, are also phenotypically distinct, insofar as they are 50% CD8+, mainly V delta 1+ V gamma 9- and CD4- CD5-. IEL show poor proliferative responses to PHA, anti-CD3 and phorbol ester/calcium ionophore in vitro and have no clear functional role: they neither provide helper nor suppressor functions for Ig synthesis by B cells and do not mediate spontaneous cytotoxicity. However, there is evidence that IEL show preferential activation in response to sheep erythrocytes, presumably signalling via CD2. As normal and inflamed intestinal epithelia do not express ICAM-1, it seems unlikely that the LFA-1/ICAM-1 interaction is of importance to IEL activation. Rather, the CD2 (LFA-2) interaction with LFA-3 expressed by enterocytes may serve both to anchor IEL and to provide an accessory stimulus for activation. Nevertheless, the questions of antigenic specificity and immunological role remain unanswered.

Expression of MHC class II antigens (HLA-DR, -DP, and -DQ) on human gastric epithelium

Class II antigen expression on gastric epithelium was investigated using an immunoperoxidase method in relation to the degree of inflammatory cell infiltration in the lamina propria. Sixty-six biopsy specimens from 43 patients with chronic gastritis were examined. The frequency of HLA-DR expression in specimens with cell infiltration was 94%, while that in specimens without cell infiltration was 24%. There was significant difference in the frequency of HLA-DR expression between the two groups (P less than 0.01). HLA-DR was most intensely expressed in the glandular neck portion. The frequency and extent of class II antigen expression on gastric epithelium with cell infiltration were in the following order: DR greater than DP greater than DQ. The extent of DR and DP, but not DQ expression generally paralleled the degree of cell infiltration. Intestinal metaplasia was found in 13 specimens. In the area of intestinal metaplasia, epithelial class II staining was absent except for one specimen. These results suggest that the respective genes of three class II antigens are regulated by different mechanisms and that an immunological mechanism plays a role in the pathogenesis of gastritis.

Hypotheses on the pathogenesis and natural history of Helicobacter pylori-induced inflammation

Although Helicobacter pylori is now recognized as playing an etiologic role in chronic gastritis and peptic ulcer disease, information on the pathogenesis and natural history of infection is limited. A model is proposed in which luminal H. pylori secrete substances that mediate inflammation that is beneficial to the organism but ultimately deleterious for the host; in addition to tissue damage, inflammation also affects gastric secretory function. In this model, the host may attempt to suppress the inflammatory response, and the adequacy of this postulated down-regulation determines pathological and clinical outcome. The effects of the inflammatory process on gastrin-hydrochloric acid homeostasis may be of critical importance in the pathogenesis of peptic ulcer disease. Because the long-term consequences of H. pylori colonization reflect the continued presence of the organism in the host over years or decades, it may be useful to consider this as a "slow" bacterial infection.

Does the stomach adapt to Helicobacter pylori?

To shed some light on the question of gastric adaptation to Helicobacter pylori infection, an overview is given of the various histopathological and clinical consequences of H. pylori infection in man. H. pylori infection can be considered as a chronic bacterial infection. For many individuals there is a balance between a low degree of infection and a low degree of inflammation. The microbial or host factors in adaptation of this balance are largely unknown. If and how 'downregulation' of the inflammatory/immune response does occur need further study.

Mucosal tumour necrosis factor alpha and interleukin-6 in patients with Helicobacter pylori associated gastritis

The production of tumour necrosis factor alpha (TNF alpha) and interleukin-6 by human antral mucosa during short term culture in vitro has been measured by enzyme linked immunosorbent assay. TNF alpha and interleukin-6 concentrations in culture supernatants were significantly greater (p less than 0.001) in patients infected with Helicobacter pylori, all of whom had chronic gastritis, than in patients who were H pylori negative with histologically normal gastric mucosa. Among H pylori colonised patients, TNF alpha concentrations were significantly higher in those with active gastritis and neutrophil infiltration into the epithelium than in those with inactive gastritis. In contrast, interleukin-6 concentrations were raised in both active and inactive gastritis. This study shows that H pylori gastritis is associated with increased gastric mucosal production of TNF alpha and interleukin-6 and that the nature of the mucosal cytokine response varies with the immunohistology of the disease. Inflammatory cytokines generated locally within the gastric mucosa could be relevant to the gastric physiology of H pylori infection.

Helicobacter pylori infection induces antibodies cross-reacting with human gastric mucosa

The authors' previous observation that many of the monoclonal antibodies against Helicobacter pylori cross-react with the cells of the human gastric mucosa prompted them to investigate the possibility that gastric self-antigens cross-reacting with H. pylori could be involved in the immune response against this organism. It was found that three antibodies against H. pylori, CB-4, CB-10, and CB-14, that cross-react with the human gastric mucosa also intensely cross-reacted with murine gastric epithelial cells. A strong reaction against autologous mucosa was also evident in the sera of mice immunized with H. pylori but not with other bacteria. A serological study performed in a group of 82 patients undergoing gastroscopy showed that the presence of seropositivity against H. pylori was strongly correlated with the presence of autoantibodies against human antral gastric mucosa. This activity was neutralized after absorption of the sera with H. pylori but not with other gram-negative bacteria. The antibodies in the mouse and in the human did not react with other segments of the gastrointestinal tract or with most of the other organs. Mice bearing hybridomas secreting a cross-reacting antibody (CB-4) had histopathologic abnormalities in their stomachs. These lesions were absent in the stomachs of mice bearing hybridomas secreting a non-cross-reacting antibody (CB-26). It was concluded that H. pylori infection can stimulate antibodies cross-reacting with gastric autoantigens and that this immunologic mechanism may represent a pathogenic link between H. pylori and gastritis.