Control of regulatory T cell development by the transcription factor Foxp3

Regulatory T cells engage in the maintenance of immunological self-tolerance by actively suppressing self-reactive lymphocytes. Little is known, however, about the molecular mechanism of their development. Here we show that Foxp3, which encodes a transcription factor that is genetically defective in an autoimmune and inflammatory syndrome in humans and mice, is specifically expressed in naturally arising CD4+ regulatory T cells. Furthermore, retroviral gene transfer of Foxp3 converts naïve T cells toward a regulatory T cell phenotype similar to that of naturally occurring CD4+ regulatory T cells. Thus, Foxp3 is a key regulatory gene for the development of regulatory T cells.

Interleukin-1 polymorphisms associated with increased risk of gastric cancer

Helicobacter pylori infection is associated with a variety of clinical outcomes including gastric cancer and duodenal ulcer disease. The reasons for this variation are not clear, but the gastric physiological response is influenced by the severity and anatomical distribution of gastritis induced by H. pylori. Thus, individuals with gastritis predominantly localized to the antrum retain normal (or even high) acid secretion, whereas individuals with extensive corpus gastritis develop hypochlorhydria and gastric atrophy, which are presumptive precursors of gastric cancer. Here we report that interleukin-1 gene cluster polymorphisms suspected of enhancing production of interleukin-1-beta are associated with an increased risk of both hypochlorhydria induced by H. pylori and gastric cancer. Two of these polymorphism are in near-complete linkage disequilibrium and one is a TATA-box polymorphism that markedly affects DNA-protein interactions in vitro. The association with disease may be explained by the biological properties of interleukin-1-beta, which is an important pro-inflammatory cytokine and a powerful inhibitor of gastric acid secretion. Host genetic factors that affect interleukin-1-beta may determine why some individuals infected with H. pylori develop gastric cancer while others do not.

Pathogenesis of Helicobacter pylori infection

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori.

Homeostatic maintenance of natural Foxp3(+) CD25(+) CD4(+) regulatory T cells by interleukin (IL)-2 and induction of autoimmune disease by IL-2 neutralization

Interleukin (IL)-2 plays a crucial role in the maintenance of natural immunologic self-tolerance. Neutralization of circulating IL-2 by anti–IL-2 monoclonal antibody for a limited period elicits autoimmune gastritis in BALB/c mice. Similar treatment of diabetes-prone nonobese diabetic mice triggers early onset of diabetes and produces a wide spectrum of T cell–mediated autoimmune diseases, including gastritis, thyroiditis, sialadenitis, and notably, severe neuropathy. Such treatment selectively reduces the number of Foxp3-expressing CD25⁺ CD4⁺ T cells, but not CD25⁻ CD4⁺ T cells, in the thymus and periphery of normal and thymectomized mice. IL-2 neutralization inhibits physiological proliferation of peripheral CD25⁺ CD4⁺ T cells that are presumably responding to normal self-antigens, whereas it is unable to inhibit their lymphopenia-induced homeostatic expansion in a T cell–deficient environment. In normal naive mice, CD25^low CD4⁺ nonregulatory T cells actively transcribe the IL-2 gene and secrete IL-2 protein in the physiological state. IL-2 is thus indispensable for the peripheral maintenance of natural CD25⁺ CD4⁺ regulatory T cells (T reg cells). The principal physiological source of IL-2 for the maintenance of T reg cells appears to be other T cells, especially CD25^low CD4⁺ activated T cells, which include self-reactive T cells. Furthermore, impairment of this negative feedback loop via IL-2 can be a cause and a predisposing factor for autoimmune disease.

Helicobacter pylori SabA adhesin in persistent infection and chronic inflammation

Helicobacter pylori adherence in the human gastric mucosa involves specific bacterial adhesins and cognate host receptors. Here, we identify sialyl-dimeric-Lewis x glycosphingolipid as a receptor for H. pylori and show that H. pylori infection induced formation of sialyl-Lewis x antigens in gastric epithelium in humans and in a Rhesus monkey. The corresponding sialic acid-binding adhesin (SabA) was isolated with the "retagging" method, and the underlying sabA gene (JHP662/HP0725) was identified. The ability of many H. pylori strains to adhere to sialylated glycoconjugates expressed during chronic inflammation might thus contribute to virulence and the extraordinary chronicity of H. pylori infection.

Helicobacter pylori-induced gastric inflammation and gastric cancer

Helicobacter pylori (H. pylori) infect over half of the world's population. The prevalence of H. pylori infection and the predominant genotype of H. pylori virulence factors vary considerably across different geographical regions. H. pylori could uniquely persist for decades in the harsh stomach environment, where it damages the gastric mucosa and changes the pattern of gastric hormone release, thereby affects gastric physiology. By utilizing various virulence factors, H. pylori targets different cellular proteins to modulate the host inflammatory response and initiate multiple "hits" on the gastric mucosa, resulting in chronic gastritis and peptic ulceration. Among the long-term consequences of H. pylori infection is gastric malignancies, particularly gastric cancer (GC) and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. As such, H. pylori has been recognized as a class I carcinogen by the International Agency for Research on Cancer. Despite a close causal link between H. pylori infection and the development of gastric malignancies, the precise mechanisms involved in this process are still obscure. Studies over the past two decades have revealed that H. pylori exert oncogenic effects on gastric mucosa through a complex interaction between bacterial factors, host factors, and environmental factors. Numerous signaling pathways can be activated by H. pylori. In this review, we aim to elaborate on the recent developments in the pathophysiological mechanisms of H. pylori-induced gastric inflammation and gastric cancer.

Organ-specific autoimmune diseases induced in mice by elimination of T cell subset. I. Evidence for the active participation of T cells in natural self-tolerance; deficit of a T cell subset as a possible cause of autoimmune disease

Organ-specific autoimmune diseases such as oophoritis, gastritis, thyroiditis, and orchitis were induced in female or male nude (nu/nu) mice by the transfer of nu/+spleen cells from which particular Lyt T cell subset(s) had been removed: nu/+spleen cells treated with anti-Lyt-1 plus complement (C) caused disease in recipient nude mice; anti-Lyt-2 plus C-treated spleen cells, in contrast, did not. The cells responsible for disease induction are believed to be Thy-1+, Lyt-1-, 2,3- (Thy-1, Lyt-1, 2,3), since spleen cells treated with mixed antisera, including anti-Lyt-1 and anti-Lyt-2, plus C, could induce the disease with almost the same incidence as anti-Lyt-1 plus C-treated cells (oophoritis 50%, gastritis 25%, thyroiditis 10-20%, and orchitis 40%). Cells treated with mixed antisera of anti-Thy-1, anti-Lyt-1, and anti-Lyt-2, plus C, could not induce autoimmune disease. Each induced autoimmune disease could be adoptively transferred to other nude mice via spleen cells, with resulting histological lesion of corresponding organs and development of specific circulating autoantibodies. Since anti-Thy-1 plus C treatment of donor spleen cells abrogated the capacity to transfer the disease, we conclude that T cells are required as effector cells, and that these may develop from Lyt-1-, 2,3- cells. Lyt-1+, 2,3- cells were demonstrated to have suppressive activity upon the development of the diseases; induction of autoimmunity was completely inhibited by the cotransfer of Lyt-1+, 2,3- cells with Lyt-1-, 2,3- cells. When anti-Lyt-2 plus C-treated cells (i.e., Lyt-1+, 2,3- and Lyt-1-, 2,3- cells) were mixed with anti-Lyt-1 and anti-Lyt-2 plus C-treated cells (i.e., Lyt-1-, 2,3- cells) in various ratios, then transferred to nude mice, the development of each autoimmune disease was clearly inhibited, even by small doses of Lyt-1+, 2,3- cells. The autoimmune disease we were able to induce was quite similar to human organ-specific autoimmune disease in terms of the spectrum of organs involved, histopathological features, and the development of autoantibodies to corresponding organ components (oocytes, parietal cells, thyroid colloid, including thyroglobulin, and sperm).(ABSTRACT TRUNCATED AT 400 WORDS)

Long-term sequelae of Helicobacter pylori gastritis

Chronic Helicobacter pylori gastritis has been put forward as a risk factor for development of gastric mucosal atrophy and gastric cancer. The purpose of our study was to investigate the long-term effects of H pylori gastritis on the gastric mucosa. We prospectively studied 49 subjects negative for H pylori and 58 positive subjects for a mean follow-up of 11.5 years (range 10-13 years). Serum samples were obtained at the initial and follow-up visits for determination of H pylori IgG antibodies. Gastroscopies with biopsy sampling were done in all patients at both visits. Biopsy specimens were used for assessment of H pylori infection and histology. Development of atrophic gastritis and intestinal metaplasia occurred in 2 (4%) uninfected and 16 (28%) infected subjects. Regression of atrophy was noted in 4 (7%) infected subjects. Development of atrophic gastritis and intestinal metaplasia was significantly associated with H pylori infection (p = 0.0014; odds ratio 9.0, 95% CI 1.9-41.3). The proportion of atrophic gastritis in the study population showed an annual increase of 1.15% (0.5-1.8%). We conclude that H pylori infection is a significant risk factor for development of atrophic gastritis and intestinal metaplasia. Our findings support strongly the causative role of this infection in gastric carcinogenesis.

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.

Mucosal IgA recognition of Helicobacter pylori 120 kDa protein, peptic ulceration, and gastric pathology

The gastric IgA response to Helicobacter pylori was examined in 100 dyspeptic patients by means of immunoblotting of supernatants from antral biopsy and gastric mononuclear cell cultures. 76 of 78 patients with chronic gastritis, 2 of 8 with reactive gastritis, and 1 of 14 subjects with normal mucosa showed positive responses. Of patients with chronic gastritis, 75%, 83%, 97% and 76%, respectively, showed responses to the 120 kDa, 90 kDa, 61 kDa, and 31 kDa proteins. None of the 19 patients with chronic gastritis who did not recognise the 120 kDa protein had peptic ulcers, whereas 25 of 57 with positive recognition had peptic ulcers (p less than 0.001). Mucosal recognition of the H pylori 120 kDa protein was also positively associated with the activity of gastritis (polymorph infiltration) (p less than 0.002) and with the extent of surface degeneration (p less than 0.01). These findings suggest that 120-kDa-positive strains of H pylori have pathogenic features associated with active gastritis and peptic ulceration. Infection with 120-kDa-negative strains may explain why peptic ulceration develops in only a proportion of subjects infected with H pylori.

Development of a mouse model of Helicobacter pylori infection that mimics human disease

The human pathogen Helicobacter pylori is associated with gastritis, peptic ulcer disease, and gastric cancer. The pathogenesis of H. pylori infection in vivo was studied by adapting fresh clinical isolates of bacteria to colonize the stomachs of mice. A gastric pathology resembling human disease was observed in infections with cytotoxin-producing strains but not with noncytotoxic strains. Oral immunization with purified H. pylori antigens protected mice from bacterial infection. This mouse model will allow the development of therapeutic agents and vaccines against H. pylori infection in humans.

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.

The lifestyle of naturally occurring CD4+ CD25+ Foxp3+ regulatory T cells

Numerous studies over the past 10 years have demonstrated the importance of naturally occurring CD4+ CD25+ Foxp3+ regulatory T cells (nTregs) in immune regulation. We analyzed the mechanism of action of nTregs in a well-characterized model of autoimmune gastritis and demonstrated that nTregs act at an early stage of disease progression to inhibit the differentiation of naïve T cells to pathogenic T-helper 1 effectors. The effects of nTregs in this model are not antigen-specific but are mediated by activation of the nTregs by ubiquitous self-peptide major histocompatibility complex class II complexes together with cytokines released by activated effector cells. Studies in vitro confirmed that some nTregs exist in an activated state in vivo and can be activated to exert non-specific suppressor effector function by stimulation with interleukin-2 in the absence of engagement of their T-cell receptor. Natural Tregs can differentiate in vitro to exhibit potent granzyme B-dependent, partially perforin-independent cytotoxic cells that are capable of specifically killing antigen-presenting B cells. Natural Treg-mediated killing of antigen-presenting cells may represent one pathway by which they can induce long-lasting suppression of autoimmune disease.

Anisakis simplex: from obscure infectious worm to inducer of immune hypersensitivity

Infection of humans with the nematode worm parasite Anisakis simplex was first described in the 1960s in association with the consumption of raw or undercooked fish. During the 1990s it was realized that even the ingestion of dead worms in food fish can cause severe hypersensitivity reactions, that these may be more prevalent than infection itself, and that this outcome could be associated with food preparations previously considered safe. Not only may allergic symptoms arise from infection by the parasites ("gastroallergic anisakiasis"), but true anaphylactic reactions can also occur following exposure to allergens from dead worms by food-borne, airborne, or skin contact routes. This review discusses A. simplex pathogenesis in humans, covering immune hypersensitivity reactions both in the context of a living infection and in terms of exposure to its allergens by other routes. Over the last 20 years, several studies have concentrated on A. simplex antigen characterization and innate as well as adaptive immune response to this parasite. Molecular characterization of Anisakis allergens and isolation of their encoding cDNAs is now an active field of research that should provide improved diagnostic tools in addition to tools with which to enhance our understanding of pathogenesis and controversial aspects of A. simplex allergy. We also discuss the potential relevance of parasite products such as allergens, proteinases, and proteinase inhibitors and the activation of basophils, eosinophils, and mast cells in the induction of A. simplex-related immune hypersensitivity states induced by exposure to the parasite, dead or alive.

Concurrent enteric helminth infection modulates inflammation and gastric immune responses and reduces helicobacter-induced gastric atrophy

Helicobacter pylori is causally associated with gastritis and gastric cancer. Some developing countries with a high prevalence of infection have high gastric cancer rates, whereas in others, these rates are low. The progression of helicobacter-induced gastritis and gastric atrophy mediated by type 1 T-helper cells may be modulated by concurrent parasitic infection. Here, in mice with concurrent helminth infection, helicobacter-associated gastric atrophy was reduced considerably despite chronic inflammation and high helicobacter colonization. This correlated with a substantial reduction in mRNA for cytokines and chemokines associated with a gastric inflammatory response of type 1 T-helper cells. Thus, concurrent enteric helminth infection can attenuate gastric atrophy, a premalignant lesion.

Induction of various cytokines and development of severe mucosal inflammation by cagA gene positive Helicobacter pylori strains

BACKGROUND

Helicobacter pylori strains possessing the cagA gene are thought to induce interleukin 8 (IL-8) in gastric mucosa. However, it is still unclear whether a relation exists between the cagA gene and the expression patterns of cytokines other than IL-8.

AIMS

To investigate the relation between the cagA gene and the production of various cytokine proteins using an enzyme linked immunosorbent assay (ELISA).

PATIENTS AND METHODS

In 184 patients, the cagA gene was detected by polymerase chain reaction (PCR), and levels of production of IL-1 beta, IL-6, IL-7, IL-8, IL-10, and tumour necrosis factor alpha (TNF-alpha) in antral biopsy specimens were measured by ELISA.

RESULTS

Mucosal levels of IL-1 beta, IL-6, IL-8, and TNF-alpha were significantly higher in H pylori positive than in H pylori negative patients. Furthermore, the mucosal levels of IL-1 beta and IL-8 were significantly higher in specimens infected with cagA positive strains than in those infected with cagA negative strains. In H pylori positive patients, the mucosal level of IL-8 was closely correlated with that of IL-1 beta (p < 0.0001), and the mucosal level of IL-6 was closely correlated with that of TNF-alpha (p < 0.0001).

CONCLUSION

These findings suggest that the ability to induce cytokines differs among the strains; cagA+ strains induce various kinds of cytokines and may cause severe inflammation, whereas cagA- strains induce IL-8 and IL-1 beta only weakly and may cause only mild inflammation. However, as most patients infected with the cagA+ strains have gastritis, these strains may not be equivalent to ulcerogenic strains.

Helicobacter pylori-induced mucosal inflammation is Th1 mediated and exacerbated in IL-4, but not IFN-gamma, gene-deficient mice

To elucidate the pathogenesis of Helicobacter pylori-associated gastritis, we studied immune responses of C57BL/6J wild-type (WT), SCID, and gene deficient (IFN-gamma-/- and IL-4-/-) mice following infection with a pathogenic isolate of H. pylori (SPM326). During early infection in WT mice, mononuclear and polymorphonuclear cells accumulated in the gastric lamina propria, and the numbers of cells in the inflamed mucosa expressing IFN-gamma, but not IL-4, mRNA rose significantly (p < 0.005), consistent with a local Th1 response. Splenic T cells from the same infected WT mice produced high levels of IFN-gamma, no detectable IL-4, and low amounts of IL-10 following in vitro H. pylori urease stimulation, reflecting a systemic Th1 response. Infected C57BL/6J SCID mice did not develop gastric inflammation despite colonization by many bacteria. Infected C57BL/10J and BALB/c mice also did not develop gastric inflammation and displayed a mixed Th1/Th2 splenic cytokine profile. These data imply a major role for the Th1 cytokine IFN-gamma in H. pylori-associated gastric inflammation in C57BL/6J mice. Compared with WT animals, infected IL-4-/- animals had more severe gastritis and higher levels of IFN-gamma production by urease-stimulated splenocytes (p < 0.01), whereas IFN-gamma-/- mice exhibited no gastric inflammation and higher levels of IL-4 production by stimulated splenocytes. These findings establish C57BL/6J mice as an important model for H. pylori infection and demonstrate that up-regulated production of IFN-gamma, in the absence of the opposing effects of IL-4 (and possibly IL-10), plays a pivotal role in promoting H. pylori-induced mucosal inflammation.

Diagnosis of Helicobacter pylori infection with a new non-invasive antigen-based assay. HpSA European study group

BACKGROUND

Helicobacter pylori is a common human pathogen implicated in certain gastrointestinal diseases. In the search for new non-invasive techniques to diagnose H. pylori infection, we evaluated an EIA for H. pylori antigen in stool (HpSA).

METHODS

In a prospective multicentre study, stool specimens from 501 patients (276 men, 225 women; age range 17-88 years, mean 52) undergoing gastroscopy in 11 centres throughout Europe were tested with HpSA and the carbon-13-urea breath test. At endoscopy, four biopsy samples were taken for histology (haematoxylin and eosin) and H. pylori detection (giemsa in both antrum and corpus, culture and rapid urease test). Patients were defined as positive for H. pylori if histology (antrum, corpus, or both) and urease test were positive, or if culture was positive. Patients classified as having H. pylori infection received an eradication regimen; 107 were reassessed 4 weeks after therapy.

FINDINGS

Of 272 patients with H. pylori infection by the predefined criteria, 256 were positive by HpSA (sensitivity 94.1% [95% CI 90.6-96.6]). Of 219 patients without infection, 201 were negative by HpSA (specificity 91.8% [87.3-95.1]).

INTERPRETATION

The stool assay was a reliable and easy-to-use tool for diagnosis of H. pylori infection. The test was accurate even shortly after treatment.

Interleukin-8 expression in Helicobacter pylori infected, normal, and neoplastic gastroduodenal mucosa

AIMS

To investigate the expression of interleukin-8 (IL-8) in Helicobacter pylori infected normal and neoplastic gastroduodenal mucosa, and in established gastric cancer cell lines.

METHODS

Immunofluorescence techniques were used to localise IL-8 in cryosections of gastric (n = 25) and duodenal (n = 17) endoscopic biopsy specimens an in resected gastric tumour tissue samples from 16 patients. Two gastric cancer cell lines (Kato 3 and MKN 45) were examined for IL-8 protein expression by immunofluorescence and for the presence of IL-8 mRNA by reverse transcription followed by the polymerase chain reaction (RT-PCR).

RESULTS

IL-8 was localised to the epithelium in histologically normal gastric mucosa, with particularly strong expression in the surface cells. IL-8 expression was also a feature of surface epithelium in the duodenal bulb, but was much reduced in the second part of the duodenum. In chronic H pylori-associated gastritis gastritis gastric epithelial IL-8 expression was increased and expression of IL-8 within the lamina propria was evident. By contrast, large areas of IL-8 negative epithelium were observed in the body mucosa of a subject with Ménétrier's disease. In gastric carcinoma the tumour cells were positive for IL-8. IL-8 was also detected by immunofluorescence in unstimulated Kato 3 and MKN 45 cells, and constitutive IL-8 gene expression in these cell lines was confirmed by detection of IL-8 mRNA by RT-PCR.

CONCLUSIONS

Immunoreactive IL-8, a potent neutrophil chemotactic and activating factor, is present in the epithelium of both normal and inflamed gastric mucosa with increased expression in the latter. There is site dependent variation in epithelial IL-8 expression within the gastroduodenal mucosa. The expression of the pro-inflammatory cytokine IL-8 in gastric carcinoma cells may influence peritumoural cellular infiltrates.

Local cytokine response in Helicobacter pylori-infected subjects

The host immune response to Helicobacter pylori infection might be of importance with regard to the outcome of infection by this organism, e.g., to explain why only a proportion of infected subjects develop peptic ulcers. In this study we have analyzed the local response of different cytokines-i.e., the proinflammatory interleukin-1beta, (IL-1beta), IL-6, tumor necrosis factor alpha, and IL-8; the immunoregulatory gamma interferon (IFN-gamma); and IL-4; and the anti-inflammatory transforming growth factor beta (TGF-beta)-in antral biopsy specimens from H. pylori-infected duodenal ulcer (DU) patients and asymptomatic (AS) carriers (i.e., with chronic gastritis only). For comparison, biopsy specimens from uninfected healthy individuals were also analyzed. An immunohistochemical technique was used to allow quantification of the cytokine responses as well as identification of the cell types associated with the cytokine expression. We found that the levels of all of the studied cytokines except IL-4 were increased in the H. pylori-infected subjects compared to the levels in the healthy individuals. Our results indicate that the antral cytokine response is of the Th1 type since IFN-gamma, but not IL-4, was up-regulated both in H. pylori-infected DU patients and in AS carriers. However, there were no significant differences in either proinflammatory or immunoregulatory cytokine levels when H. pylori-infected subjects with and without peptic ulcers were compared. Some of the cytokines, particularly IL-1beta and TGF-beta, were also found in the gastric mucosae of healthy, uninfected subjects. We also showed that the gastric epithelium contributes substantially to the antral cytokine response of the proinflammatory cytokines IL-1beta and IL-6 in addition to IL-8.

Cutting edge: depletion of CD4+CD25+ regulatory T cells is necessary, but not sufficient, for induction of organ-specific autoimmune disease

Thymectomy of BALB/c mice on day 3 of life results in the development of autoimmune gastritis (AIG) due to the absence of CD4(+)CD25(+) regulatory T cells. However, depletion of CD4(+)CD25(+) T cells by treatment with anti-CD25 rarely resulted in AIG. Depletion was efficient, as transfer of splenocytes from depleted mice induced AIG in nu/nu mice. One explanation for this result is that CD4(+)CD25(-) T cells upon transfer to nude recipients undergo lymphopenia-induced proliferation, providing a signal for T cell activation. Cotransfer of CD25(+) T cells did not inhibit initial proliferation but did suppress AIG. Surprisingly, immunization with the AIG target Ag, H/K ATPase, in IFA failed to induce disease in normal animals but induced severe AIG in CD25-depleted mice. These results demonstrate that second signals (nonspecific proliferation, TCR activation, or inflammation) are needed for induction of autoimmunity in the absence of CD25(+) regulatory T cells.

Diagnostic value of decreasing IgG, IgA, and IgM antibody titres after eradication of Helicobacter pylori

Titres of antibody to Helicobacter pylori are known to fall with eradication of bacteria. To find out what degree of fall would reliably indicate eradication, 144 patients with Helicobacter pylori infection were given antimicrobial therapy for 2 weeks and then followed up at 6 weeks, 6 months, and 12 months with serological tests, bacterial cultures, and histological studies of gastric specimens. 6 weeks after treatment IgG titres had fallen by 20-30% irrespective of the success of bacterial eradication. In the 121 bacteria-negative patients the decrease continued. 6 and 12 months after treatment the titre was 50% or less of pretreatment value in 97% of these patients. In the 23 patients who remained infected, the initial drop of IgG titres, if any, was followed by unchanged or slightly rising titres. IgA and IgM titres, initially raised in 64% and 4% of the patients, respectively, showed similar trends. The high sensitivity (97%) of the IgG antibody tests and a consistent fall within 6 months after eradication of H pylori infection made IgG the most useful immunoglobulin class for follow-up of antimicrobial therapy in individual patients. IgA antibodies were valuable in the 2% patients who had raised titres in this immunoglobulin class only. The few patients (5.5%) who had raised IgM titres also had high IgG titres. Serological tests thus are a cheap and reliable means of monitoring success of eradication of H pylori.

Surface proteins from Helicobacter pylori exhibit chemotactic activity for human leukocytes and are present in gastric mucosa

The mechanism by which Helicobacter pylori, a noninvasive bacterium, initiates chronic antral gastritis in humans is unknown. We now show that H. pylori releases products with chemotactic activity for monocytes and neutrophils. This chemotactic activity was inhibited by antisera to either H. pylori whole bacteria or H. pylori-derived urease. Moreover, surface proteins extracted from H. pylori and purified H. pylori urease (a major component of the surface proteins) exhibited dose-dependent, antibody-inhibitable chemotactic activity. In addition, a synthetic 20-amino acid peptide from the NH2-terminal portion of the 61-kD subunit, but not the 30-kD subunit, of urease exhibited chemotactic activity for monocytes and neutrophils, localizing the chemotactic activity, at least in part, to the NH2 terminus of the 61-kD subunit of urease. The ability of leukocytes to chemotax to H. pylori surface proteins despite formyl-methionyl-leucyl-phenylalanine (FMLP) receptor saturation, selective inhibition of FMLP-mediated chemotaxis, or preincubation of the surface proteins with antiserum to FMLP indicated that the chemotaxis was not FMLP mediated. Finally, we identified H. pylori surface proteins and urease in the lamina propria of gastric antra from patients with H. pylori-associated gastritis but not from uninfected subjects. These findings suggest that H. pylori gastritis is initiated by mucosal absorption of urease, which expresses chemotactic activity for leukocytes by a mechanism not involving N-formylated oligopeptides.