Topographic expression of MUC5AC and MUC6 in the gastric mucosa infected by Helicobacter pylori and in associated diseases

We investigated the topographic expression of MUC5AC and MUC6 in relationship with gastric diseases. The immunoexpression of MUC5AC and MUC6 was evaluated in 75 adults presenting Helicobacter pylori gastritis (n = 22; 11 cagA positive), duodenal ulcer (DU, n = 11), gastric ulcer (GU, n = 9), gastric carcinoma (GC, n = 20), and normal mucosa (H. pylori negative, n = 13). Five gastric areas (antral and corporeal lesser and greater curvatures and incisura) were studied. H. pylori was detected by carbolfuchsin, urease, and culture; cagA was determined by PCR. All patients with DU (eight with GU and 13 with GC) were H. pylori-positive. In H. pylori gastritis, MUC5AC expression was higher in the antrum than in the corpus; no difference was observed with respect to cagA status. MUC5AC expression was higher in the antrum of gastritis than in DU, and it was lower in the incisura among GU patients compared to DU. MUC6 expression was higher in the antrum of H. pylori gastritis compared to DU and to uninfected patients. No difference was observed in the topographic pattern of expression of MUC5AC and MUC6 among GC cases. The topographic over- and under-expression of mucins in H. pylori-associated gastritis and peptic disease suggest a role for these mucins in the pathogenesis of H. pylori infection and associated diseases.     

Pathology of the gastric antrum and body associated with Helicobacter pylori infection in non-ulcerous patients: is the bacterium a promoter of intestinal metaplasia?

A series of 115 consecutive, non-ulcerous, dyspeptic patients were examined for Helicobacter pylori (H. pylori) colonization in the gastric antral and/or body mucosa using Giemsa staining. Findings were correlated with the presence and degree of activity of superficial gastritis, deep gastritis, atrophic gastritis and with the presence of intestinal metaplasia. The prevalence of H. pylori positivity was 61.7%. In 59 of the 71 positive patients (83%), H. pylori was detected in the antrum or in both the antral and oxyntic mucosa. In the remaining 12 positive patients, H. pylori was detected only in the oxyntic mucosa and in all these cases, the antrum showed intestinal metaplasia associated with atrophic gastritis (25%). In both antral and oxyntic mucosa, the activity of the gastritis was significantly correlated with H. pylori colonization. Linear logistic regression analysis showed that in patients with intestinal metaplasia the presence of H. pylori infection was significant in predicting the presence of more extensive intestinal metaplasia after adjusting for age. The prevalence of intestinal metaplasia types II and III was 65.5% in the H. pylori positive and 25% in the H. pylori negative patients. The antral mucosa is thought to be the elective site for H. pylori related histological lesions. At a later stage, H. pylori can be detected only in the oxyntic area while the antral mucosa shows extensive metaplastic or atrophic lesions. We would suggest that H. pylori plays a promotional role in the morphogenesis of intestinal metaplasia.     

Correlation of Helicobacter pylori virulence genotypes vacA and cagA with histological parameters of gastritis and patient's age.

The histological parameters of Helicobacter pylori (H. pylori) gastritis are dependent on the virulence factor profile of the microbe, which includes the cytotoxins vacA (vacuolating cytotoxin A) and cagA (cytotoxin-associated gene A) as well as the duration of infection. The virulence factor genotypes vacA and cagA were assessed by the line probe reverse hybridization assay INNO-LiPA and correlated with the histological parameters of H. pylori infection, in particular intestinal metaplasia (IM) as well as with the patient's age. A total of 120 patients were analyzed; 47 patients with IM in the antrum and 73 control patients without this alteration. The vacA s1 cagA+ genotype (high virulence) correlated with the presence of antral IM, a more intense acute inflammation in both antrum and corpus and the formation of ulcer. The vacA m1 genotype (high virulence) correlated with a more intense acute inflammation in only the corpus as well as more prominent Russell bodies in the antrum. H. pylori strains with the vacA s2 m2 cagA- genotype (low virulence) were rarely found in these conditions (all P <0.05). No correlation with the virulence status was found for the type and extent of IM, the intensity of chronic inflammation, the formation of lymphoid follicles and the microbial density. Furthermore, patients with IM were 7 years older than their counterparts without (P<0.05). Finally, there was a trend for more virulent vacA s1 m1 cagA+ strains to be found in younger individuals (P>0.05). The virulence genotype of the microbe is an important determinant for the severity of the gastritis and the formation of antral IM. Age is an additional factor for the development of IM.     

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.     

Relation between IgG and IgA antibody titres against Helicobacter pylori in serum and severity of gastritis in asymptomatic subjects.

AIMS--To investigate whether the absorbance index of IgG and IgA antibodies against Helicobacter pylori is related to a semiquantitative assessment of the density of H pylori colonisation in gastric biopsy specimens and to the severity of gastritis. METHODS--The grade of gastritis was scored separately for antral and fundic mucosa using three different classifications. Serum IgA and IgG antibodies against H pylori were measured by ELISA. The density of gastric H pylori colonisation was graded semiquantitatively from 0 to 3. RESULTS--Among 48 healthy volunteers studied, 17 were found to have gastritis according to Whitehead''s criteria. H pylori was present in the biopsy specimens of 14 of 17 subjects with gastritis. The IgG H pylori antibody absorbance index was significantly (p < 0.05) correlated not only with the density of antral H pylori colonisation, but also with the degree of gastritis of the antrum, as assessed by the Whitehead score, activity, and the Sydney system (p < 0.05). The IgA H pylori antibody absorbance index was significantly correlated with the Whitehead score and Sydney system, but not with the activity score of the antrum or with the density of antral gastric H pylori infection. There were no significant correlations between the IgG H pylori antibody absorbance index and the gastritis scores of the fundus mucosa and the density of H pylori infection of the gastric body. The IgA H pylori antibody absorbance index was only significantly (p < 0.05) correlated with the density of H pylori colonisation and the Sydney system gastritis score of the corpus. CONCLUSIONS--The serological absorbance index of IgG antibodies against H pylori is related to the severity of antral gastritis and the density of antral H pylori colonisation. Thus a high absorbance index of IgG antibodies against H pylori points to severe antral gastritis and dense H pylori colonisation of the antrum.     

Gastrin (G) cells and somatostatin (D) cells in patients with dyspeptic symptoms: Helicobacter pylori associated and non-associated gastritis

BACKGROUND: Gastrin G cells and somatostatin D cells are important regulators of gastric acid secretion and alterations in their relative numbers may play a key role in gastroduodenal disease. AIM: To investigate the effect of Helicobacter pylori infection on the density of immunoreactive G and D cells in gastric antral and corpus biopsies from patients with dyspeptic complaints. METHODS: One hundred and twenty two patients with dyspeptic complaints had two antrum and two corpus biopsies taken during upper endoscopy. The severity of inflammation and the density of H pylori were evaluated semiquantitatively. In addition, the density and distribution of neuroendocrine cells, especially G and D cells, were examined using immunohistochemistry. Patients were divided into three groups, those with H pylori positive gastritis, H pylori negative gastritis, and histologically normal gastric mucosa. RESULTS: The number of immunoreactive G cells was significantly higher and the number of immunoreactive D cells lower in patients with H pylori positive gastritis compared with H pylori negative gastritis or histological normal gastric mucosa. The percentage of G cells as a percentage of mucosal endocrine cells was also raised and that of D cells was decreased. CONCLUSIONS: Helicobacter pylori infection produces alterations in the number of endocrine cells responsible for regulating acid secretion in relation to intragastric pH and feeding. The alterations correlate best with the severity of inflammation and not with H pylori density.     

Topographical localisation of cagA positive and cagA negative Helicobacter pylori strains in the gastric mucosa; an in situ hybridisation study

BACKGROUND: The cagA gene is a marker for the presence of the cag pathogenicity island, and the presence of cagA positive strains of Helicobacter pylori can identify individuals with a higher risk of developing gastrointestinal diseases. AIMS: To study the interaction between H. pylori cagA(+) and cagA(-) strains and the gastric mucosa. METHODS: Patients with H. pylori associated gastritis and peptic ulcers were studied. Biopsies were obtained from the antrum, corpus, fundus, and incisura for H pylori culture, and for in situ hybridisation studies. From each biopsy, multiple single H. pylori colonies were isolated and propagated for DNA isolation, and cagA was detected by the polymerase chain reaction (PCR). For in situ detection of H. pylori an oligonucleotide specific for an H. pylori common antigen and an oligonucleotide specific for cagA were used as probes. Biotinylated probes were incubated with biopsy sections, developed with streptavidin-horseradish peroxidase, and amplified with the tyramide system. RESULTS: PCR results for cagA in isolated colonies confirmed the in situ hydridisation studies. In situ hybridisation identified cagA(+) bacteria in patients with cagA(+) isolates; cagA(-) bacteria in patients with cagA(-) isolates, and cagA(+) and cagA (-) bacteria in patients with both cagA(+) and cagA(-) isolates. CagA(-) bacteria usually colonised the mucous gel or the apical epithelial surface, whereas cagA(+) bacteria colonised the immediate vicinity of epithelial cells or the intercellular spaces. CONCLUSIONS: These results document a different in vivo interaction between H. pylori cagA(+) or cagA(-) strains and the gastric mucosa.     

Improvement of gastric inflammation and resolution of epithelial damage one year after eradication of Helicobacter pylori.

AIMS--To investigate the effect of eradication of Helicobacter pylori infection on gastric epithelial damage and gastritis, scored according to the Sydney system. METHODS--Gastritis scores and epithelial damage were assessed in gastric biopsy specimens before, and five weeks and one year after anti-H pylori therapy in 66 patients with H pylori related gastritis. RESULTS--The mean initial levels of activity, inflammation, atrophy, intestinal metaplasia, and H pylori scores were higher in the antrum than in the corpus or fundus. Eradication of H pylori resulted in an improvement in the mean inflammatory score in antral biopsy specimens from 2.23 before treatment to 1.32 and 1.06, respectively, five weeks and one year after treatment. Corresponding values for fundic biopsy specimens were 1.30, 0.36 and 0.35. Activity scores improved from 1.41 before treatment to 0.13 and zero, respectively, five weeks and one year after treatment in antral biopsy specimens and from 0.60 before treatment to zero in fundic biopsy specimens. Before treatment, epithelial damage was present in 51% of biopsy specimens taken from the antrum and 23% of those from the corpus. Five weeks after eradication of H pylori none of the biopsy specimens revealed evidence of epithelial damage. CONCLUSION--Eradication of H pylori is followed by a rapid, significant improvement in the gastritis score and resolution of epithelial damage in antral and fundic mucosa.     

In patients with Helicobacter pylori gastritis and functional dyspepsia, a biopsy from the incisura angularis provides useful diagnostic information

The aim of this study was to assess whether the taking of an additional biopsy from the incisura angularis increases the chance of detecting maximal degrees of atrophy and intestinal metaplasia (IM) in patients with Helicobacter pylori gastritis and functional dyspepsia. At entry into a randomised trial, biopsies were taken from 328 patients (mean age 48 years), two from both the gastric antrum and corpus, and one from the incisura angularis, and comparative grading of gastritis variables was carried out. Biopsy material from the gastric antrum, corpus, and the incisura angularis revealed no notable differences in atrophy or an incidence of IM and mucosa-associated lymphatic tissue. However, when the incisura biopsies were classified histologically, 58% contained antral mucosa (AM), 18% corpus mucosa (CM), and 24% intermediate zone mucosa. AM at the incisura was associated with considerably more severe gastritis in both the incisura and antrum (14% atrophy, 20% IM) than in CM of incisura (2% atrophy, 6% IM). Corpus atrophy and IM were rare in the AM group and absent from the CM group. Incisura angularis biopsy in patients with H. pylori gastritis and functional dyspepsia does give additional information regarding the severity of gastritis expected in the corpus and antrum. Antral-type mucosa in the incisura angularis region seems to indicate an increased risk for the development of atrophy and/or IM.     

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.     

Role of corpus gastritis and cagA-positive Helicobacter pylori infection in reflux esophagitis

Considering that the role of Helicobacter pylori infection in gastroesophageal reflux and reflux esophagitis (GERD) is still controversial and that the role of virulence markers of the bacterium has not been evaluated in most studies of GERD, we investigated the association among H. pylori infection with cagA-positive and -negative strains, corpus gastritis, and GERD in a large group of patients by controlling for confounding factors. We studied prospectively 281 consecutive adult patients: 93 with GERD and 188 controls. H. pylori infection status was diagnosed by culture, by the preformed urease test, with a carbolfuchsin-stained smear, and by histology. The cagA status was determined by PCR of H. pylori isolates and gastric biopsy specimens. H. pylori infection was diagnosed in 191 (68.0%) of 281 patients. Among the 93 patients with GERD, 84 presented with mild or moderate esophagitis and 9 presented with severe esophagitis. In the multivariate analysis, the age of the patients and the degree of oxyntic gastritis were associated with GERD. Among the strains isolated from patients with GERD and from the control group, 24.4 and 66.9%, respectively, were positive for cagA (P < 0.001). Compared to infection with cagA-negative strains, infection with cagA-positive H. pylori strains was associated with a more intense gastritis in the corpus (P = 0.001). cagA status (odds ratio [OR] = 0.16, 95% confidence interval [CI] = 0.07 to 0.40), gastritis of the corpus (OR = 0.69, 95% CI = 0.48 to 0.99), and age (OR = 1.04, 95% CI = 1.01 to 1.07) were associated with GERD. In conclusion, the study provides evidence supporting the independent protective roles of cagA-positive H. pylori strains and the degree of corpus gastritis against GERD.     

The phenotype of gastric mucosa coexisting with Barrett's oesophagus

BACKGROUND/AIMS: Barrett's oesophagus complicates the gastro-oesophageal acid reflux. Helicobacter pylori infection, particularly with cagA positive strains, induces inflammatory/atrophic lesions of the gastric mucosa, which may impair acid output. No systematic study has investigated the phenotype of the gastric mucosa coexisting with Barrett's oesophagus. This study was designed to identify the phenotype of gastric mucosa associated with Barrett's oesophagus. METHODS: In this retrospective case control study, the phenotype of the gastric mucosa was histologically characterised in 53 consecutive patients with Barrett's oesophagus and in 53 (sex and age matched) non-ulcer dyspeptic controls. Both patients and controls underwent extensive sampling of the gastric mucosa (two antral, one incisural, and two oxyntic biopsies). Intestinal metaplasia (IM) was categorised (type I, complete IM; types II and III, incomplete IM) by the high iron diamine stain; cagA status was ascertained by genotyping. RESULTS: Helicobacter pylori was present in 19 of the 53 patients with Barrett's oesophagus and in 30 of the 53 controls (p < 0.02); eight of the 19 patients with Barrett's oesophagus and 28 of the 35 controls harboured cagA positive H pylori (p < 0.03). The histological severity of non-atrophic gastritis detected in the controls was significantly higher than that detected in the patients with Barrett's oesophagus (p < 0.0001). Multifocal atrophic gastritis was present in 4% of the patients with Barrett's oesophagus and in 23% of controls (p < 0.01). The odds ratio for the association between multifocal atrophic gastritis and Barrett's oesophagus was 0.20 (95% confidence interval, 0.006 to 0.60). Gastric IM was detected in 13.2% of the patients with Barrett's oesophagus and in 30.1% of the controls (p < 0.03). Type III IM at the gastric mucosa was only detected among controls. CONCLUSIONS: Barrett's oesophagus is associated with a low prevalence of H pylori cagA positive infection and multifocal atrophic gastritis. This pathobiological pattern is considered to be associated with a low risk of distal gastric cancer.     

Mast cells in Helicobacter pylori associated antral gastritis

Mast cells are known to be effector cells in various inflammatory reactions, but their role in gastritis is unclear. The present study was undertaken to investigate the extent of mast cell involvement in antral gastritis with and without Helicobacter pylori (H. pylori) infection and thus evaluate the possible role of mast cells in the pathogenesis of H. pylori-associated gastritis. Antral mucosal biopsies were taken from 212 subjects with symptoms suggestive of acid peptic disease. Sections were assessed for inflammation. Modified Giemsa stain was used to detect H. pylori infection and 1% toluidine blue to count mast cells. Mast cell counts were significantly higher in the antral mucosa even in H. pylori-negative gastritis (68.4 +/- 6.7/mm2), as compared to normal non-inflamed mucosa (45.7 +/- 5.8/mm2) (P < 0.05). However, with H. pylori infection, the mucosal mast cell count were markedly increased (123.8 +/- 4.7/mm2) as compared to normal mucosa (P < 0.01). and H. pylori-negative gastritis (P < 0.01) this increase was noticed uniformly in patients with H. pylori-positivity, irrespective of the presence or absence of a peptic ulcer. After cure of H. pylori infection, the mast cell density decreased significantly (44.9 +/- 4.6/mm2) to reach levels that were similar to those in normal mucosa. There was a positive correlation between the antral mucosal mast cell density and polymorphonuclear and mononuclear cell infiltration (rs = 0.61). H. pylori infection, and 0.73 respy. It was concluded that could be responsible for increasing the mast cell density in the gastric antrum. Probably by inducing castain mucosal cytokine.     

Involvement of mast cells in gastritis caused by Helicobacter pylori: a potential role in epithelial cell apoptosis

BACKGROUND: The role(s) of mast cells (MC) in gastric mucosal inflammation caused by Helicobacterpylori is (are) still debated. AIM: To determine whether there is an association between MC density and epithelial cell apoptosis in antral gastric mucosa infected by H pylori. Patients and methods: Biopsy specimens from 122 H pylori-positive subjects with chronic active gastritis, 84 patients with non-steroidal anti-inflammatory drug-induced gastritis and 48 volunteers were included. H pylori genotypes were determined by PCR amplification of bacterial cultures. Immunohistochemical analysis was performed on tissue microarrays with anti-CD117, anti-chymase, anti-tryptase, anti-myeloperoxidase, anti-Bcl-2, anti-Bcl-x, anti-Bax and anti-caspase 3 antibodies. RESULTS: Of the 122 patients infected with H pylori, 76 (62.3%) harboured cagA positive strains. H pylori isolates belonged to the vacAs1/m1 genotype in 82 (67%) cases, to the vacAs2/m2 genotype in 23 (18.8%) cases and to the vacAs1/m2 genotype in 17 (13.9%) cases. 61 (50%) H pylori isolates were babA2+. In patients infected with H pylori, the density of MC, and in particular the number of MC-associated epithelial cells, was correlated with a high number of apoptotic epithelial cells. Moreover, the density of MC was correlated with the number of neutrophils infiltrating the antral gastric mucosa, and was strongly increased in patients infected with cagA, vacAs1/m1 and babA2 positive strains. CONCLUSIONS: Taken together, these data show that the density of MC can be considered as a histopathological criterion of gastritis activity in patients infected with H pylori.     

Up-regulation of cathepsin X in Helicobacter pylori gastritis and gastric cancer

Recently, we identified increased cathepsin X expression in H. pylori-infected gastric mucosa. Here, we describe further up-regulation in gastric cancer and report on the role of inflammatory cytokines required for cathepsin X up-regulation in H. pylori-infected gastric mucosa, as well as on consequences for cellular invasion. Biopsy specimens were taken from the antrum, corpus and cardia of H. pylori-infected and non-infected patients. Gastric cancer samples were obtained from patients undergoing gastric surgery. Cathepsin X was detected in gastric mucosa by quantitative real-time RT-PCR, western blotting and immunohistochemistry. Induction of cathepsin X expression in epithelial and inflammatory cells caused by H. pylori infection was tested in in vitro contact and non-contact co-cultures of AGS cells and monocytic cells. Patients with H. pylori gastritis showed significantly higher cathepsin X mRNA (2.5-fold) and protein (1.6-fold) expression than H. pylori-negative patients. Cathepsin X was also up-regulated in gastric cancer (3-12-fold) compared to non-neoplastic mucosa. Cathepsin X was predominantly expressed by macrophages in the mucosal stroma and in glands of the antral mucosa. In addition, tumour cells stained for cathepsin X in 26 (68%) patients with gastric carcinoma. In general, staining was significantly more common (20 vs. 6 patients) and more intense (3.55 vs. 0.83) in intestinal type gastric cancer than in the diffuse type. In vitro cell culture experiments revealed that intercellular signalling between pathogenicity island (PAI)-positive H. pylori-infected epithelial cells and macrophages via soluble factors in the culture medium seems to be responsible for increased expression of cathepsin X in monocytes. Using antisense oligonucleotides, cathepsin X up-regulation was directly associated with higher invasiveness in vitro. Although no correlation of cathepsin X expression and TNM stage was found, our study demonstrates that cathepsin X plays a role not only in the chronic inflammation of gastric mucosa but also in the tumourigenesis of gastric cancer.     

The prevalence of lymphoid follicles in Helicobacter pylori associated gastritis in patients with ulcers and non-ulcer dyspepsia.

AIMS--To determine the prevalence of lymphoid follicles in Helicobacter pylori positive and negative gastritis in antral and body type gastric mucosa in patients with non-ulcer dyspepsia (NUD), duodenal ulcer, or gastric ulcer; to correlate follicle presence with patient age; to evaluate the correlation between the prevalence of lymphoid follicles and active and inactive gastritis and its severity; and to assess the positive predictive value of lymphoid follicle prevalence with respect to H pylori infection. METHODS--Gastric biopsy specimens, graded according to the Sydney system, from 337 patients were studied. RESULTS--Lymphoid follicles occurred more often in antral mucosa (78%) than in body type mucosa (41%) and were observed in 85% of patients with H pylori positive gastritis. There was no significant difference between NUD and gastric and duodenal ulcer disease with regard to the presence of lymphoid follicles. The positive predictive value of the presence of lymphoid follicles in H pylori infection was 96%. Lymphoid follicles were more commonly observed in patients aged between 10 and 29 years. Lymphoid follicles were more frequently found in pangastritis of all subtypes than in antral gastritis and also in active gastritis than in inactive gastritis. The presence of lymphoid follicles correlated strongly with the degree and severity of gastritis. CONCLUSION--Lymphoid follicles are a constant morphological feature of H pylori associated gastritis.     

Association of Helicobacter pylori with HLA-DR antigen expression in gastritis.

AIMS: To assess the association between Helicobacter pylori-associated gastritis and HLA-DR antigen (class II antigen) expression. METHODS: Fifty endoscopic gastric biopsy specimens were studied for the presence of H pylori, degree and type of inflammation, and for HLA-DR antigen expression in the epithelium. The cases were chosen to represent different categories: inflamed gastric mucosa with (n = 13) and without (n = 20) H pylori, and non-inflamed mucosa (n = 17). RESULTS: The antigen was aberrantly expressed in the antral mucosal epithelium in 11 of 12 cases (92%) with acute-on-chronic gastritis when H pylori was also present. It was present in the antrum in only seven of 18 H pylori negative cases (39%) with acute-on-chronic/chronic gastritis. One of three cases of acute gastritis and three of seven cases of chronic gastric erosions (non-inflamed category) showed positive staining. Generally, there was more staining in the antral than body mucosa and in the surface/foveolar epithelium than in the glands. No aberrant HLA-DR antigen expression was found in the 10 cases of normal gastric mucosa examined. CONCLUSIONS: These findings suggest that H pylori may have a role in the induction of class II HLA antigen expression in chronic gastritis and lend support to the view that these organisms may be responsible for part of the inflammatory response.