The Story So Far: Helicobacter Pylori and Gastric Autoimmunity

The gastric mucosal pathogen Helicobacter pylori induces autoantibodies directed against the gastric proton pump H⁺,K⁺-ATPase in 20–30% of infected patients. The presence of these autoantibodies is associated with severity of gastritis, increased atrophy, and apoptosis in the corpus mucosa, and patients with these autoantibodies infected with H. pylori display histopathological and clinical features that are similar to those of autoimmune gastritis (AIG). This review will focus on the T helper cell responses, cytokines, and adhesion molecules involved in corpus mucosal atrophy in chronic H. pylori gastritis and in AIG, and the role of H. pylori in the onset of AIG.     

Helicobacter pylori und antigastrale Autoimmunität

Recent studies report a significant association between Helicobacter pylori gastritis and autoimmune reaction. Antigastric autoantibodies are detectable in about 30% of H. pylori infected patients. Two major in situ binding sites have been found: first, at the luminal membrane of the foveolar epithelium in antrum and corpus mucosa and, second, at canalicular membranes within parietal cells in the corpus mucosa. The presence of latter type of autoantibodies is correlated with histological and clinical parameters of corpus mucosa atrophy. The gastric H+/K(+)-ATPase, which is already known as an autoantigen in classic autoimmune gastritis, also represents a major target in atrophic H. pylori gastritis. According to recent data molecular mimicry between H. pylori and the host does not play a pathogenic role in the formation these autoantibodies. In conclusion, antigastric autoimmunity represents a relevant host factor which contributes to the final outcome of H. pylori gastritis.     

Induction of follicular gastritis following postthymectomy autoimmune gastritis in Helicobacter pylori-infected BALB/c mice

Helicobacter pylori is the major causative agent of chronic antral gastritis and is thought to be involved in the pathogenesis of mucosa-associated lymphoid tissue lymphoma (MALToma) developing in the human stomach. The aim of this study was to clarify whether corporal autoimmune gastritis (AIG), which is known to decrease acidity due to destruction of parietal cells, predisposes mice to H. pylori infection, thereby leading to MALToma-like pathology. BALB/c mice in which AIG had been induced by thymectomy 3 days after birth (AIG mice) were used. The AIG mice were orally administered mouse-adapted H. pylori at the age of 6 weeks and were examined histologically and serologically after 2 to 12 months. The results were compared with those obtained from uninfected AIG mice and infected normal mice. Germinal centers were induced in the corpus in 57% of the H. pylori-infected AIG mice, which elicited anti-H. pylori antibody responses in association with upregulation of interleukin-4 (IL-4) mRNA. In these mice, parietal cells remained in the corpus mucosa. These findings were in contrast to those with the uninfected AIG mice: fundic gland atrophy due to disappearance of parietal cells associated with upregulation of gamma interferon, but not IL-4, mRNA and no germinal center formation in the corpus. These observations suggest that AIG alters the infectivity of H. pylori, leading to MALToma-like follicular gastritis, at an early stage after H. pylori infection.     

Gastric mucosal inflammation and epithelial cell turnover are associated with gastric cancer in patients with Helicobacter pylori infection

BACKGROUND: Infection with a virulent Helicobacter pylori strain is associated with gastric mucosal damage and the increased risk of gastric cancer. AIMS: To examine the characteristics of host gastric mucosal responses in patients with gastric cancer, histological grade of gastritis, gastric epithelial apoptosis, and proliferation were studied. METHODS: Thirty two patients with early gastric cancer and 32 sex and age matched controls were studied. All subjects were infected with a virulent H pylori strain (vacA s1/m1, cagA positive genotype). Biopsy specimens were taken from the antrum and the corpus of the stomach. The grade of gastritis was assessed according to the updated Sydney system. Apoptotic cells were detected using terminal uridine deoxynucleotidyl nick end labelling, and epithelial cell proliferation was determined by means of the Ki-67 labelling index. RESULTS: In patients with gastric cancer, significantly higher grades were observed when glandular atrophy (p < 0.05) and intestinal metaplasia (p < 0.01) were present in the antrum, and when mononuclear cell infiltration was present in the corpus (p < 0.05). The numbers of apoptotic cells were increased in patients with cancer (p < 0.05) and the apoptotic index correlated significantly with the grade of glandular atrophy. Epithelial cell proliferation was more likely to be increased in mucosa where intestinal metaplasia was present. CONCLUSIONS: Infection with H pylori causes increased gastric epithelial apoptosis, resulting in more severe glandular atrophy in patients with gastric cancer. Increased damage of gastric epithelial DNA and the presence of more severe atrophic gastritis might contribute to the development of gastric cancer.     

Evidence of novel pathogenic pathways for the formation of antigastric autoantibodies in Helicobacter pylori gastritis.

Autoantibodies against gastric epithelial cells are detectable in up to 50% of patients with chronic, active Helicobacter pylori gastritis. Presence of autoantibodies against canalicular structures within human parietal cells (anticanalicular autoantibodies) correlate with gastric mucosa atrophy. It has been suggested, that molecular mimicry between H pylori and the host on the level of Lewis X and Lewis Y blood group antigens leads to these autoantibodies. This study aimed at analysing whether antigastric antibodies can be absorbed to Lewis X or Y positive H pylori strains. Sera from 14 H pylori infected patients with anticanalicular autoantibodies were effectively absorbed to H pylori. Immunohistochemical studies of the absorbed sera showed no decrease of antigastric autoreactivity. Pathogenic mechanisms other than molecular mimicry lead to the formation of antigastric autoantibodies, and epitopes other than Lewis antigens are the autoimmune targets.     

Helicobacter pylori infection and chronic gastritis in gastric cancer.

AIMS: To investigate the prevalence of Helicobacter pylori associated chronic gastritis in patients with gastric cancer. METHODS: Serum IgG antibodies for H pylori were determined in 54 consecutive patients with gastric carcinoma. The prevalence of H pylori in gastric mucosa was also examined histologically (modified Giemsa) in 32 patients from whom adequate biopsy specimens of the antrum and corpus were available. Thirty five patients with gastrointestinal tumours outside the stomach and 48 with non-gastrointestinal malignancies served as controls. RESULTS: Of the 54 patients, 38 (70%) had H pylori antibodies (IgG) in their serum (three additional patients had H pylori antibodies IgA, class specific but not IgG specific). This prevalence was significantly higher (p less than 0.05) than that (49%) in the 35 controls. No differences in prevalence of H pylori antibodies were found between gastric cancer cases of intestinal (IGCA) or diffuse (DGCA) type, both these types showing H pylori antibodies (IgG) in 71% of the patients. In the subgroup of 32 subjects, five patients had normal gastric mucosa and four showed corpus limited atrophy ("pernicious anaemia type" atrophy of type A). All of these nine patients had no evidence of current or previous H pylori infection in serum (no IgG antibodies) or in tissue sections (negative Giemsa staining). The remaining 23 patients had antral or pangastritis, and all had evidence of current or previous H pylori infection. CONCLUSIONS: H pylori associated chronic gastritis was the associated disease in 75% of the patients with gastric cancer occurring equally often in both IGCA and DGCA groups. About 25% of cases seem to have a normal stomach or severe corpus limited atrophy, neither of which showed evidence of concomitant H pylori infection.     

Features of gastritis predisposing to gastric adenoma and early gastric cancer

BACKGROUND/AIMS: Helicobacter pylori gastritis is a risk factor for the development of gastric cancer. The results of several studies indicate that gastric adenomas, which are considered premalignant lesions, may also be associated with H pylori gastritis. However, it is not clear whether there are different patterns of gastritis in these patients compared with patients with gastric cancer or patients with H pylori gastritis alone. Therefore, this study was designed to investigate the patterns of gastritis in these three groups of patients. METHODS: The histological features of gastric mucosa at a distance from the tumour were analysed prospectively in 118 patients with gastric adenoma (mean age, 71.8; female to male ratio, 6 : 4). In addition, for every patient with H pylori associated gastric adenoma an age and sex matched control patient with either H pylori associated early gastric cancer of the intestinal type or H pylori gastritis only was investigated. RESULTS: Only 60 patients (50.9%) with gastric adenoma were infected with H pylori. In the remaining patients, complete atrophic gastritis predominated. In those patients with adenoma and H pylori infection, the gastritis was similar to that seen in patients with early gastric cancer (median score, 2 for activity and degree of gastritis in the antrum and corpus); intestinal metaplasia was common to both groups. These two groups differed significantly from patients with H pylori gastritis only (median grade and activity of gastritis, 1 in antrum and corpus), in whom intestinal metaplasia was rare. CONCLUSIONS: It appears that gastric adenomas and gastric intestinal cancer arise by analogous mechanisms. However, owing to severe atrophic gastritis and a lower incidence of H pylori, adenomas do not appear to be definite precursor lesions for gastric cancer.     

Response of IgG1 and IgG2 subclasses to Helicobacter pylori in subjects with chronic inflammation of the gastric mucosa, atrophy and gastric cancer in a country with high Helicobacter pylori infection prevalence

Polarized immune response to Helicobacter pylori and induction of chronic inflammation may increase the risk of gastric atrophy and adenocarcinoma. We studied the association of the response of IgG1 and IgG2 antibodies to H. pylori with grade of gastric chronic inflammation and atrophy in a population with a high prevalence of H. pylori, and compared these data with the data obtained from the study of gastric cancer patients, as well as with the data for CagA positivity. Altogether, 114 persons from two adult population samples from Estonia and 45 consecutive gastric cancer patients were studied. All patients were positive for the H. pylori antibody determined by ELISA. Adenocarcinoma was classified histologically according to the Laurén's system. The response of the IgG subclasses to H. pylori (acid glycine-extracted whole cell proteins) was determined by ELISA and the results were compared with the ELISA results for the recombinant fragment of the CagA protein. Helicobacter pylori IgG level was lower in atrophic gastritis compared with nonatrophic gastritis (chronic inflammation) (p=0.001). In the group of cancer patients, the response of IgG and IgG1 was lower compared with both gastritis groups (p=0.01 and p=0.0002 for IgG, and p=0.001 and p=0.0005 for IgG1). IgG2 was lower for gastric cancer localized in the corpus (p=0.03). In conclusion, atrophic gastritis and gastric cancer were associated with a significant decline in IgG and IgG1 response to H. pylori compared with nonatrophic gastritis. Higher value of CagA antibodies was seen in gastric cancer and in gastric atrophy compared with nonatrophic gastritis; in gastric cancer patients, IgG1 response to H. pylori was correlated with CagA status.     

Contribution of epidemiological studies to gastritis immunology

Chronic gastritis, or chronic inflammation in gastric antral and/or corpus mucosa, is a common pathological condition affecting over half the general population. Progression of chronic gastritis from Helicobacter pylori infection to severe gastric mucosal atrophy usually takes decades and varies considerably from person to person. Therefore, studies of clinically selected material cannot provide a complete picture of natural evolution of the disease or its wide variability. An overview of immunological and morphological aspects of chronic gastritis in an epidemiological context, based on data from the literature and the author's studies, reveal dynamic interaction between H. pylori infection and host response to the organism's antigens, and to gastric autoantigens including gastric H+K+ ATPase. Further population and followup studies of antral and corpus gastritis at different stages of evolution are needed, in combination with new methods, to elucidate further the roles of infection, and gastric-antrum- and corpus-mucosa-related autoimmune responses, in the pathogenesis of chronic gastritis.     

Expression of melanoma differentiation associated gene 5 is increased in human gastric mucosa infected with Helicobacter pylori

Helicobacter pylori infection is associated with gastroduodenal diseases. Melanoma differentiation associated gene 5 (MDA5) plays a role in antiviral host defense. We investigated the effect of H pylori infection on MDA5 expression in human gastric mucosa. Biopsy samples from the antrum and corpus were obtained from 33 patients. MDA5 mRNA and protein were examined by real-time PCR and immunohistochemical staining. Histological gastritis was graded according to updated Sydney System. MDA5 mRNA was significantly increased in the antrum infected with H pylori. MDA5 protein positively stained in infiltrating mononuclear cells. MDA5 mRNA expression was significantly correlated with the grade of glandular atrophy (rs = 0.767) and intestinal metaplasia (rs = 0.748) in the corpus with H pylori infection. These results indicate that MDA5 may be involved in innate immune reactions against H pylori and associate with glandular atrophy and intestinal metaplasia in patients with H pylori infection.     

Impact of Helicobacter pylori eradication on morphological changes in gastric mucosa

The purpose of the study was to examine gastric mucosal morphological changes in patients with gastroduodenal pathology after eradication therapy for Helicobacter pylori (H. pylori). A hundred and thirty-eight patients (40 females and 98 males) were examined. Of them, there were 122 patients with duodenal peptic ulcer, 8 with gastric peptic ulcer, 5 with erosive gastritis, 2 with chronic atrophic antral gastritis, and 1 with non-atrophic gastritis. Two months and a year after therapy, manifestations of gastric mucosal atrophy, the degree of inflammation, and its activity significantly diminished in patients with complete H. pylori eradication. Positive changes were observed mainly in the antral portion of the stomach. In patients with partial eradication, chronic inflammation and its activity became less. Two months and a year following therapy, positive changes in the gastric mucosa were absent in patients without H. pylori eradication.     

Role of activated protein C in Helicobacter pylori-associated gastritis

The protein C (PC) pathway has recently been suggested to play a role in the regulation of the inflammatory response. To further extend the anti-inflammatory effect of activated PC (APC) in vivo, particularly its biological relevance to human disease, the activity of APC in the mucosa of patients with Helicobacter pylori-associated gastritis and the effect of vacuolating cytotoxin (VacA), cytotoxin-associated antigen (CagA), and H. pylori lipopolysaccharide (LPS) on PC activation were evaluated. This study comprised 35 patients with chronic gastritis. There were 20 patients with and 15 without H. pylori infection. The levels of PC and APC-PC inhibitor (PCI) complex were measured by immunoassays. The level of PC was significantly decreased and the level of APC-PCI complex was significantly increased in biopsy specimens from gastric corpus and antrum in patients with H. pylori-associated gastritis as compared to H. pylori-negative subjects. The concentrations of VacA, CagA, and LPS were significantly correlated with those of the APC-PCI complex in biopsy mucosal specimens from the gastric corpus and antrum. H. pylori LPS, VacA, and CagA induced a dose-dependent activation of PC on the surface of monocytic cells. APC inhibited the secretion of tumor necrosis factor alpha (TNF-alpha) induced by H. pylori LPS. Overall, these results suggest that H. pylori infection is associated with increased APC generation in the gastric mucosa. The inhibitory activity of APC on TNF-alpha secretion may serve to protect H. pylori-induced gastric mucosal damage.     

Expression and subcellular distribution of toll-like receptors TLR4, TLR5 and TLR9 on the gastric epithelium in Helicobacter pylori infection

Toll-like receptors (TLRs) expressed by mucosal epithelium play an essential role in the defense against microbes by recognizing conserved bacterial molecules. For the first time TLR4, TLR5 and TLR9 have been microanatomically localized in patients with noninflamed gastric mucosa and Helicobacter pylori gastritis by immunohistochemistry. Because polarized expression of TLRs in apical and basolateral epithelial compartments is thought to modulate mucosal immunity, subcellular TLR distribution by gastric epithelium was investigated using confocal microscopy. TLR4, TLR5 and TLR9 were expressed by gastric epithelium in antrum and corpus of all patients with H. pylori gastritis (n = 14) and with noninflamed gastric mucosa (n = 5). TLR4 was expressed at the apical and the basolateral pole of the gastric epithelium as well in noninflamed gastric mucosa as in H. pylori gastritis. TLR5 and TLR9 expression in the noninflamed gastric mucosa was identical to that of TLR4 with localization at the apical and the basolateral epithelial pole. However, in H. pylori gastritis TLR5 and TLR9 expression on the gastric epithelium changed to an exclusive basolateral localization without detectable expression at the apical pole. In the human stomach, the gastric epithelium expressed TLR4, TLR5 and TLR9, which gives it the possibility to interact with H. pylori. Furthermore, gastric epithelial TLR4 expression is highly polarized in an apical and a basolateral compartment, whereas TLR5 and TLR9 polarization seems to be a process dynamically influenced by H. pylori infection. This polarized and dynamically regulated gastric epithelial expression of TLRs supports a sentinel role for these receptors in the mucosal immunity to H. pylori.     

Atrophic gastritis in young children and adolescents

BACKGROUND: Helicobacter pylori associated gastric cancer arises via a multistage process, with atrophic gastritis being the precursor lesion. Helicobacter pylori is typically acquired in childhood, yet little is known of the prevalence of atrophic gastritis in childhood. AIM: To study atrophic gastritis among children from countries with high gastric cancer incidence. METHODS: Sections from topographically mapped gastric biopsy specimens from children undergoing clinically indicated endoscopy in Korea and Colombia were evaluated using visual analogue scales. Atrophy was defined as loss of normal glandular components, including replacement with fibrosis, intestinal metaplasia (IM), and/or pseudopyloric metaplasia of the corpus (identified by the presence of pepsinogen I in mucosa that was topographically corpus but phenotypically antrum). RESULTS: One hundred and seventy three children, 58 from Korea (median age, 14 years) and 115 from Colombia (median age, 13 years), were studied. Helicobacter pylori was present in 85% of Colombian children versus 17% of Korean children (p<0.01). Atrophic mucosa near the antrum-corpus border was present in 16% of children, primarily as pseudopyloric metaplasia (31%, IM; 63%, pseudopyloric metaplasia; 6%, both). The median age of children with corpus atrophy was 15 (range, 7-17) years. CONCLUSION: Gastric atrophy occurs in H pylori infected children living in countries with high gastric cancer incidence. Identification and characterisation of the natural history of H pylori gastritis requires targeted biopsies to include the lesser and greater curve of the corpus, starting just proximal to the anatomical antrum-corpus junction, in addition to biopsies targeting the antrum and cardia.     

Light and electron microscopic immunohistochemical investigation on G and D cells in antral mucosa in Helicobacter pylori-related gastritis.

Recently, it has been recognized that Helicobacter pylori (H. pylori) infection is associated with an exaggeration of basal and meal gastrin secretion. We investigate whether there is a relationship between H. pylori-related chronic gastritis and G-cell and D-cell number and granule density index of G and D cells. - The number of antral G cells and D cells and granule density index of D and G cells are compared between thirty two patients with H. pylori-related chronic gastritis and twelve patients without H. pylori and inflammation. Antral mucosal biopsy specimens are examined using light and electron immunohistochemical techniques. - The number of G cells is the same in either infected or uninfected patients (98.40 +/- 11.39, 109.25 +/- 12.76 vs 101.17 +/- 7.72 for infected patients with non atrophic and with mild atrophic chronic gastritis and uninfected controls, respectively) except for the cases with moderate gastric mucosal atrophy, where G cells (58.22 +/- 5.63) decrease in number. The number of D cells is decreased in all patients with H. pylori-related gastritis. G cell granule density index is significantly (p < 0.05) increased in patients with H. pylori-related chronic gastritis than in controls (3.15 +/- 0.43 vs 2.528 +/- 0.01). D cell granule density index is similar between patients with H. pylori chronic gastritis and controls (3.18 +/- 0.05 vs 3.166 +/- 0.12). It is concluded that decreased D cells number in patients with H. pylori-related chronic gastritis might be one of the reasons for the existing hypergastrinaemia.     

CagA in Barrett's oesophagus in Colombia, a country with a high prevalence of gastric cancer

BACKGROUND: In the USA, atrophic gastritis and gastric cancer are rare, whereas gastro-oesophageal reflux disease (GERD) is common. Infection with Helicobacter pylori, especially a CagA positive strain, is unusual in patients with GERD/Barrett's oesophagus in the USA. AIM: To examine the relation between Barrett's oesophagus and CagA positive H pylori in Colombia, a country with a high prevalence of CagA positive H pylori associated atrophic gastritis and gastric cancer. METHODS: Helicobacter pylori and CagA status was determined among Colombian patients with long segment Barrett's oesophagus and a control group with simple H pylori gastritis. Helicobacter pylori status was determined using a triple stain and CagA status was determined by immunohistochemistry using a specific rabbit anti-CagA serum. RESULTS: Gastric and oesophageal mucosal biopsies were obtained from 51 patients--39 men (mean age, 57.8 years; SD, 13.1) and 12 women (mean age, 51.8 years; SD, 14.4)--with documented long segment Barrett's oesophagus. The results were compared with 24 Colombian patients with H pylori gastritis without oesophageal disease. Thirty two patients with Barrett's oesophagus had active H pylori infection. CagA status was evaluated in a subset of 23 H pylori infected patients with Barrett's oesophagus, and was positive in eight of these patients compared with 19 of 24 controls (p = 0.01). CONCLUSIONS: Although most Colombian patients with Barrett's oesophagus had H pylori infection, CagA positive infections were unusual. These data illustrate how consistent corpus inflammation reduces acid secretion, which prevents Barrett's oesophagus among those with abnormal gastro-oesophageal reflux barriers.     

Helicobacter heilmannii gastritis: association with acid peptic diseases and comparison with Helicobacter pylori gastritis.

We analyzed 2 antral and 1 corpus full-thickness random endoscopic gastric mucosal samples obtained from 946 patients with duodenal ulcers (6077 biopsies) and from 281 patients with nonsteroidal anti-inflammatory drug-associated gastric ulcers (1794 biopsies). We stained tissue sections with hematoxylin and eosin and Warthin-Starry silver stain and immunostained them with polyclonal antibodies against Helicobacter pylori. Hematoxylin- and eosin-stained sections from 6 patients with Helicobacter heilmannii (18 biopsies) and 23 randomly selected patients with H. pylori (68 biopsies) were evaluated and semiquantitated for the presence of acute inflammation, chronic inflammation, glandular atrophy, intestinal metaplasia, H. pylori, H. heilmannii, lymphoid follicles, or vasodilatation. Additional specimens were obtained for H. pylori culture, a CLO test, and serologic examination. H. heilmannii was detected in 6 (0.49%) of 1227 patients (14 [0.18%] of 7871 biopsies). Of these, 4 (0.42%) of 946 were patients with duodenal ulcers (9 [0.15%] of 6077 biopsies), and 2 (0.71%) of 281 were patients with nonsteroidal anti-inflammatory drug-associated gastric ulcers (5 [0.28%] of 1794 biopsies). We found H. heilmannii with hematoxylin and eosin stain, Warthin-Starry stain, and immunoperoxidase stain for H. pylori. Culture for H. pylori was negative in the four patients with duodenal ulcers. The CLO and serologic tests were positive in three of five and five of five patients, respectively. Our results indicate that H. heilmannii, like H. pylori, is associated with peptic ulcer disease (both active and inactive gastritis) and that it preferentially colonizes the gastric antrum. The severity of the H. heilmannii-associated gastritis is less intense and lymphoid aggregates are less common than in H. pylori-associated gastritis. Morphologic detection seems to be the method of choice for detecting H. heilmanni. Immunoperoxidase stain specific for H. pylori also stains H. heilmannii, indicating cross-reacting antigenic epitopes between H. heilmannii and H. pylori.     

Histological study of chronic gastritis from the United Arab Emirates using the Sydney system of classification.

AIMS--To determine the prevalence of Helicobacter pylori in five main nationality groups with gastric ulcer, duodenal ulcer, and non-ulcer dyspepsia; and to determine the histopathological types of gastritis and assess the graded variables of Helicobacter associated gastritis. METHODS--Gastric antral and corpus biopsy specimens from 437 patients were examined for the prevalence of H pylori, 337 of which were classified and graded histologically according to the Sydney system. RESULTS--The overall colonisation rate of H pylori was 90%, and there was no significant difference between groups of different ethnic origins. The colonisation rates were 99%, 89%, and 78% in patients with duodenal ulcer, non-ulcer dyspepsia, and gastric ulcer, respectively. Helicobacter associated gastritis was the most common form of chronic gastritis (87%). H pylori density was greater in the antrum than the body. Gastric atrophy in helicobacter associated gastritis was seen in 54% of the cases (43% grade I, 10% grade II, 1% grade III) and increased the older the patients. Atrophy of the corpus alone was very rare (1%). Atrophy and intestinal metaplasia were more prevalent in patients with gastric ulcer than duodenal ulcer. CONCLUSION--The colonisation rate of H pylori was similar in the five groups studied and was almost invariably present in gastric biopsy specimens in patients with duodenal ulcer. H pylori associated gastritis was the most common form of gastritis. Atrophy was mainly of low grade and increased the older the patient.     

Disparity between mucosal and serum IgA and IgG in <Emphasis Type="Italic">Helicobacter pylori</Emphasis> infection

Mucosal IgA and IgG are involved in the immune defense against Helicobacter pylori in infected patients. In contrast to IgG, IgA is transported into the gastric lumen and is responsible for the first-line defense. Therefore antigens recognized by mucosal IgA are possible candidates for vaccination. This study compared the IgA and IgG immune response to H. pylori in the gastric mucosa and that in the serum of 21 patients with H. pylori gastritis by the immunoblotting technique. In particular, mucosal IgA immune response against the urease antigen of H. pylori was studied in detail, as vaccination with this antigen was not curative in men. The results show that mucosal IgA was not represented by serum IgA and IgG, and that the H. pylori specific mucosal IgA and IgG immune responses differ in antigen-recognition pattern. This disparity may reflect the different transport ways and functions of these two immunoglobulin isotypes. Furthermore, mucosal IgA specific for urease was found inconsistently in patients with H. pylori gastritis. As vaccination antigens should induce an appropriate mucosal IgA immune response against H. pylori, our findings may have important implications for the selection of antigens for vaccination against H. pylori.