TNF and LTA gene polymorphisms reveal different risk in gastric and duodenal ulcer patients

A small proportion of patients infected with Helicobacter pylori or using non-steroidal anti-inflammatory drugs (NSAIDs) develops peptic ulcer disease. Since family studies have shown the importance of the genetic background of the host in the development of gastric and duodenal ulcers, immunogenetic factors involved in the regulation of inflammation deserve further study. Polymorphisms in the genes encoding tumour necrosis factor (TNF) and lymphotoxin-alpha (LTA) have been shown to contribute to the severity of infectious disease. Our aim was to study four bi-allelic polymorphisms in the TNF and LTA genes, which occur as five haplotypes, in patients with peptic ulcer disease. A total of 130 patients with duodenal ulcer, 50 with gastric ulcer and 102 ethnically-matched Spanish Caucasian healthy controls were studied. H. pylori infection was determined by invasive and non-invasive tests. Odds ratios were obtained by logistic regression analysis. H. pylori was detected in 91.8% of peptic ulcer patients and in 73.3% of controls (P < 0.001). Patients with gastric ulcer had a lower frequency of the TNF-308 allele 2 and a higher frequency of the LTANcoI 2.2 genotype when compared with duodenal ulcer patients (P < 0.01 and P = 0.03, respectively). Carriers of haplotype TNF-I were more frequent in gastric ulcer patients (49%) than in controls (28%) (P < 0.05) and the haplotype TNF-E was significantly more frequent in duodenal ulcers than in gastric ulcers (27% vs 8.2%; P < 0.01). Logistic regression analysis identified haplotype TNF-I carrier status as an independent risk factor for peptic ulceration in H. pylori-infected patients (OR: 4.2; 95%CI: 1.7-10.2). These results suggest that TNF and LTA gene polymorphisms are related to the development of gastric and duodenal ulcer and may determine disease outcome in H. pylori infection.

Polymorphisms in the tumor necrosis factor and lymphotoxin-alpha gene region and preeclampsia

OBJECTIVE

To investigate potential association or linkage among nine polymorphisms in the genes encoding tumor necrosis factor (TNF) alpha or lymphotoxin (LT) alpha and preeclampsia.

METHODS

Four di-allelic polymorphisms and five microsatellite markers in the genes encoding TNF-alpha (TNF) and LTalpha (LTA) and their haplotypes were studied in 150 Dutch families. These families contained sib-pairs of women affected with preeclampsia; eclampsia; the hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome (strict criteria); or pregnancy-induced hypertension (mild criteria). Frequencies were compared with 98 healthy controls. Nonparametric affected sib-pair analyses for allele sharing among siblings were carried out for all nine markers. Each sibship was composed of an affected index woman and one or more affected sisters.

RESULTS

Although we found a striking association with the TNF-I haplotype in 30 index women with (pre-)eclampsia or HELLP syndrome compared with controls (odds ratio [OR] 3.8; 95% confidence interval [CI] 1.6, 8.9), this association was not found in their 30 sisters meeting similar disease criteria. Analyses in all 150 families showed a similar TNF-I association in 122 index women meeting the strict criteria compared with controls (OR 1.9; 95% CI 1.1, 3.3), but, again, not in their 91 sisters meeting similar disease criteria. This association was stronger in a subgroup of 75 index women with preeclampsia only (OR 2.3; 95% CI 1.2, 4.2). No excess allele sharing for any marker was seen between the siblings.

CONCLUSION

The nine polymorphisms studied in the TNF-LTA region did not show evidence for association or linkage with familial preeclampsia.

The polymorphic IL-1B and IL-1RN genes in the aetiopathogenesis of peptic ulcer

Besides environmental factors, the genetic background of an individual may contribute to the development and final outcome of peptic ulcer disease. Interleukin-1beta (IL-1beta) and the interleukin-1 receptor antagonist (IL-1ra) are cytokines that play a key role in modulating the inflammatory response in the gastrointestinal mucosa. This study aimed to investigate whether polymorphisms in the IL-1B and IL-RN genes are involved in the susceptibility to and final outcome of peptic ulcer disease. DNA from 179 unrelated Spanish Caucasian patients with peptic ulcer diseases and 99 ethnically matched healthy controls was typed for the TaqI polymorphism at position + 3954 in the IL-1B gene and the variable number of tandem repeats polymorphism in intron 2 of the IL-1RN gene. The determination of Helicobacter pylori status and non-steroidal anti-inflammatory drug (NSAIDs) use was studied in all patients and in controls. H. pylori infection and NSAID use were more frequent in ulcer patients than in controls. There were no significant differences in carriage rate, genotype and allele frequencies of the IL-1RN and the IL-1B(+3954) gene polymorphisms between peptic ulcer patients and controls. However, a strong allelic association between IL-1B and IL-1RN genes was found in duodenal ulcer patients (P < 0.0006). Logistic regression identified H. pylori infection and NSAIDs use as independent risk factors for peptic ulcer diseases whereas the simultaneous carriage of IL-1B(+3954) allele 2 and IL-1RN allele 2 was associated with reduced risk for duodenal ulcer disease (OR: 0.37, 95% CI = 0.14-0.9). Our data suggest that IL-1B and IL-1RN genes in addition to bacterial and environmental factors play a key role in determining the final outcome of peptic ulcer disease.

Polymorphisms of the interleukin-1 gene family, oral microbial pathogens, and smoking in adult periodontitis

Interleukin (IL)-1alpha, IL-1beta, and IL-1ra contribute to regulation of the inflammatory response in periodontal tissues. We aimed to investigate the distribution of polymorphisms in the IL-1 gene family among periodontitis patients and controls, taking into account smoking and microbiology as additional variables. Fifty-three non-smoking and 52 smoking patients with severe adult periodontitis and 53 controls were genotyped for bi-allelic IL-1A(-889), IL-1B(-3954), and a penta-allelic 86-bp VNTR IL-1RN gene polymorphisms. The presence of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans was established by culture techniques. We found a higher frequency of allele 2 carriage in IL-1A, IL-1B, and IL-1RN in periodontitis patients who were non-smokers and in whom P. gingivalis and A. actinomycetemcomitans could not be detected (42.1% vs. 11.3% in controls; P = 0.0068; OR 5.7, 95% CI: 1.6-19.8). Our results provide evidence that polymorphisms in genes of the IL-1 family are associated with severe adult periodontitis in the absence of other risk factors tested in this patient population.

Gluten challenge in borderline gluten-sensitive enteropathy

OBJECTIVES

In patients with signs and symptoms of malabsorption, suggestive of gluten-sensitive enteropathy, small intestinal biopsies sometimes only reveal infiltration of lymphocytes into the mucosal epithelium. This infiltrative lesion (Marsh I) is not a definite proof for gluten-sensitive enteropathy. However, in the present study, we aimed to show that a subgroup of these patients could ultimately be identified as being gluten sensitive.

METHODS

A total of 38 patients with a Marsh I lesion were subjected to a gluten challenge comprising 30 g of gluten added daily to a normal gluten-containing diet for 8 wk. Before and after the challenge, small intestinal biopsies were taken, and symptoms and signs of malabsorption were scored.

RESULTS

In 12 patients we demonstrated a significant change in mucosal histopathology, i.e., subtotal villous atrophy (Marsh IIIB, n = 1), partial villous atrophy (Marsh 3A, n = 6) or infiltrative-crypthyperplastic lesions (Marsh II, n = 5). In the other 26 patients, the small intestinal mucosa remained unchanged. After initiation of a gluten-free diet, follow-up small intestinal biopsies in 12 patients who initially had progressive mucosal pathology after gluten challenge showed normalization of mucosal pathology in seven cases, regression to a Marsh I lesion in four, and to a Marsh II lesion in one. Symptom relief was seen in all 12 patients. Ten of 26 patients without histological response to the gluten challenge were motivated to adhere to a gluten-free diet. Follow-up biopsies revealed unchanged Marsh I lesions in eight patients and normalization (Marsh 0) in two patients. Three patients had follow-up biopsies while on a normal diet. All had unchanged Marsh I lesions.

CONCLUSIONS

In the present study we demonstrated that a gluten challenge might be useful in identifying patients as being sensitive to gluten if initial small intestinal biopsies reveal only minor abnormalities.

Gluten challenge in borderline gluten-sensitive enteropathy

OBJECTIVES

In patients with signs and symptoms of malabsorption, suggestive of gluten-sensitive enteropathy, small intestinal biopsies sometimes only reveal infiltration of lymphocytes into the mucosal epithelium. This infiltrative lesion (Marsh I) is not a definite proof for gluten-sensitive enteropathy. However, in the present study, we aimed to show that a subgroup of these patients could ultimately be identified as being gluten sensitive.

METHODS

A total of 38 patients with a Marsh I lesion were subjected to a gluten challenge comprising 30 g of gluten added daily to a normal gluten-containing diet for 8 wk. Before and after the challenge, small intestinal biopsies were taken, and symptoms and signs of malabsorption were scored.

RESULTS

In 12 patients we demonstrated a significant change in mucosal histopathology, i.e., subtotal villous atrophy (Marsh IIIB, n = 1), partial villous atrophy (Marsh 3A, n = 6) or infiltrative-crypthyperplastic lesions (Marsh II, n = 5). In the other 26 patients, the small intestinal mucosa remained unchanged. After initiation of a gluten-free diet, follow-up small intestinal biopsies in 12 patients who initially had progressive mucosal pathology after gluten challenge showed normalization of mucosal pathology in seven cases, regression to a Marsh I lesion in four, and to a Marsh II lesion in one. Symptom relief was seen in all 12 patients. Ten of 26 patients without histological response to the gluten challenge were motivated to adhere to a gluten-free diet. Follow-up biopsies revealed unchanged Marsh I lesions in eight patients and normalization (Marsh 0) in two patients. Three patients had follow-up biopsies while on a normal diet. All had unchanged Marsh I lesions.

CONCLUSIONS

In the present study we demonstrated that a gluten challenge might be useful in identifying patients as being sensitive to gluten if initial small intestinal biopsies reveal only minor abnormalities.

Accuracy and cost-effectiveness of a new strategy to screen for celiac disease in children with Down syndrome

OBJECTIVES

To investigate the best approach to screen for celiac disease (CD) in patients with Down syndrome (DS).

STUDY DESIGN

One hundred thirty-seven children with DS were followed up longitudinally. CD screening was offered in 1994, 1996, and 1999 by determination of serum immunoglobulin A-anti-endomysium antibodies (AEA). The HLA-DQA1*0501/DQB1*02 allelic combination known to be strongly positively associated with CD was typed. All IgA-AEA-positive children were given the opportunity to undergo a small bowel biopsy: if villous atrophy was found, the diagnosis of CD was established.

RESULTS

CD was diagnosed in 11 (8%) children: 8 in 1994 and 3 in 1996. All of them carried the HLA-DQ alleles associated with CD. The presence of symptoms was not useful in discriminating which children could have CD.

CONCLUSIONS

Screening once in a lifetime is not enough to detect CD in patients with DS. We propose a new, accurate, and cost-sparing 2-step strategy for screening, based on selection of the individuals with potential CD by HLA-DQ typing and on longitudinal serologic CD screening in this selected group.

The mouthwash: a non-invasive sampling method to study cytokine gene polymorphisms

BACKGROUND

We describe a simple, non-invasive mouthwash sampling method for rapid DNA isolation to detect cytokine gene polymorphisms. In the present paper, interleukin- 1beta(IL-1B) and interleukin-1 receptor antagonist (IL-1RN) gene polymorphisms were studied.

METHODS

Two mouthwash samples and blood samples were collected from 11 healthy individuals. The second mouthwash sample was stored for 7 days at room temperature. Polymerase chain reaction amplification was used to identify a bi-allelic polymorphism at position +3953 in the IL-1B gene and a variable number of tandem repeats (VNTR) polymorphism in the IL-1RN gene.

RESULTS

Our results show that the typing of these cytokine gene polymorphisms using DNA isolated from mouthwash samples did not differ from those obtained by a phenol/chloroform isolation method from EDTA anti-coagulated blood. Moreover, reliable results from mouthwash samples were obtained after storage for at least 7 days at room temperature.

CONCLUSIONS

Mouthwash can be the method of choice to study gene polymorphisms in periodontitis and other chronic inflammatory diseases.

Cyclosporin in the treatment of adults with refractory coeliac disease--an open pilot study

AIM

To evaluate the effect of cyclosporin treatment on clinical and histological parameters in adult patients with refractory coeliac disease.

METHODS

Thirteen patients were treated with oral cyclosporin for 2 months, aiming at serum levels of 100-200 ng/mL. Seven extended medication intake up to a maximum of 12 months. Before and after treatment, clinical parameters were monitored and small intestinal biopsies taken. Ten of 13 patients were typed for HLA-DQA1 and -DQB1 alleles.

RESULTS

Eight of 13 patients responded histologically to cyclosporin treatment. Normalization of villi was demonstrated in five patients, three after prolonged treatment. Eight patients reported a clinical response, of whom six had concomitant histological improvement. No serious side-effects of cyclosporin were noticed. Nine of 10 patients who were immunogenetically typed carried the coeliac disease associated serologic DQ2 markers, one carried neither DQ2 nor DQ8 markers.

CONCLUSION

In our study group of 13 adult refractory coeliac disease patients, cyclosporin in therapeutic doses induced a histological improvement in eight patients (61%), in five of whom (38%) normalization of villi was demonstrated. Thus, we believe that cyclosporin is a therapeutic option in refractory coeliac disease, although we could not confirm earlier reports of unconditional successful treatment.

High prevalence of celiac disease in apparently healthy blood donors suggests a high prevalence of undiagnosed celiac disease in the Dutch population

BACKGROUND

In the last few years the prevalence of celiac disease (CD) seems to have increased. It is clear that subclinical and silent CD exist in a large subgroup of the celiac population.

METHODS

The aim of this study was to evaluate the prevalence of CD in an apparently healthy population. Blood samples were obtained from 1000 apparently healthy blood donors at Arnhem and Nijmegen Blood Donation Centers from January 1997 through April 1998. Sera from 660 blood donors were assayed for total IgA. By means of immunofluorescence, antibodies, including those to endomysium (EMA), were determined. Serum immunoglobulin levels (IgA) were assayed by means of nephelometry. All donors who had positive serology for EMA underwent small-intestinal biopsy.

RESULTS

Of the 1000 healthy blood donors 3 had positive EMA. Small-intestinal biopsy of two of these showed subtotal villous atrophy (Marsh IIIb), and the third had intraepithelial lymphocytosis and crypt hyperplasia (Marsh II). The prevalence of gluten sensitivity was 1 of 330. Low IgA (0.60-0.23 g/l) in our study group was found in 9 of 660 (1%), but no one showed an IgA < or = 0.02 g/l.

CONCLUSION

Our study shows that the prevalence of gluten-sensitivity in apparently healthy blood donors is 3 of 1000, which suggests a high prevalence of CD in the Dutch population, in contrast to the results of the last published Dutch epidemiologic studies. The recorded prevalence will increase further with greater recognition of subclinical and asymptomatic forms detected by screening tests.

Genetic markers in clinically well defined patients with ulcerative colitis (UC)

Results of genetic association studies in UC are conflicting. We propose that the power of candidate gene studies will increase when disease heterogeneity is taken into account. Phenotype frequencies of molecularly defined HLA-DR alleles, polymorphisms in the tumour necrosis factor-alpha (TNF-alpha), lymphotoxin-alpha (LT-alpha), IL-1 receptor antagonist (IL-1Ra) and IL-1beta genes were determined in 98 clinically well characterized UC patients with a mean period of follow up of 10 years, and ethnically matched healthy controls (HC). The alleles HLA-DRB1*0103 (phenotype frequency 6% versus 0.2%; P = 0.0002; odds ratio (OR) 27.6) and DRB1*15 (41% versus 26%; P = 0. 001; OR = 2.0, compared with HC) were associated with overall disease susceptibility. Subgroup analysis revealed that DRB1*15 was only increased in females (53% versus 24%; P < 0.0001; OR = 3.5), but not in males. With regard to disease localization, all DRB1*0103+ patients had extensive disease (P < 0.002; OR = 33.5), and DRB1*15 was found in 59% of females with extensive colitis (P < 0.0001; OR = 4.4). DRB1*0103 was significantly increased in patients undergoing colectomy (P < 0.0002; OR = 84). No association between overall disease susceptibility and the cytokine gene polymorphisms were found. Subgroup analysis revealed several significant associations, but most did not retain significance when corrected for multiple comparisons. However, a noticeable finding was that haplotype TNF-C was significantly associated with progression in extent of disease (P = 0.003, OR = 20.4). This study provides additional evidence for the role of DRB1 alleles in the susceptibility to UC, and supports the hypothesis that these alleles may determine the severity of the disease. The cytokine gene polymorphisms evaluated in this study do not seem to be strong risk factors for the overall disease susceptibility in UC, but may be involved in determining the severity of the disease.

Association of interleukin-1beta and interleukin-1 receptor antagonist genes with disease severity in MS

OBJECTIVE

To investigate whether polymorphisms in the interleukin (IL)-1beta and IL-1 receptor antagonist (IL-1RA) genes are associated with both susceptibility to and clinical characteristics of MS.

BACKGROUND

Genetic susceptibility to MS is determined by many partially identified genes. The genes encoding various cytokines are logical candidates for MS susceptibility and phenotype.

METHODS

Genotypes were determined from 148 patients with clinically definite MS and 98 healthy controls. All the patients were unrelated, Dutch, and white. Patient files were reviewed for disease type, initial symptoms, age at onset of disease, and rate of disease progression.

RESULTS

No significant differences in genotypes, allele frequencies, or carrier frequencies were found between MS patients and healthy controls. Stratification for disease type (relapsing-remitting, primary progressive, or secondary progressive) did not provide significant differences between patients and controls. However, a specific IL-1RA/IL-1beta combination was associated with disease severity. MS patients with the IL-1RA allele 2+/IL-1beta allele 2- combination had a higher rate of progression on the Expanded Disability Status Scale when compared with the other possible combinations (p = 0.007).

CONCLUSIONS

IL-1RA and IL-1beta are disease severity genes rather than disease susceptibility genes. Furthermore, these gene polymorphisms may define subgroups of patients with a worse prognosis.

Food allergy, coeliac disease and chronic inflammatory bowel disease in man

It is often stated that the gastrointestinal tract has a limited number of responses to pathogens. Entirely different agents can produce a similar histopathological reaction. However, the expression of the disease in man is very heterogeneous, it varies with the age of the subject and is to a certain extent genetically determined. For example, food allergy is frequent in childhood and not common in adulthood. The intestinal mucosa in the child with cows milk allergy shows a 'flat' mucosa, which may be indistinguishable of that observed in gluten sensitive enteropathy or coeliac disease. Subjects with other forms of food allergy may have a morphologically normal small intestinal mucosa, occasionally with increased IgE plasma cells and often only characterised by an increased intestinal permeability. An abnormal intestinal permeability is one of the hallmarks of an inflamed gut, however, subjects with a latent form of coeliac disease have an abnormal permeability only without overt signs of inflammation. Recently, it has become clear that what determines the characteristics of the intestinal inflammatory response is dependent on the cytokines involved during the response and this seems to be the same in the stomach, the small intestine and the colon. A so-called Th1 response, with an increased production of IFN-gamma, TNF-alpha and other pro-inflammatory cytokines, occurs in the stomach when infected by Helicobacter pylori, in the small intestine when the subject with coeliac disease consumes normal bread and during the active phases of Crohn's disease. A Th2 response is characteristic of the allergic subject and there is some evidence that it is the predominant response in subjects with ulcerative colitis. We still do not know the fine-tuning of the cytokine response but IL-12 appears to be a key cytokine in polarising the response to a Th1 type. More recently it has become clear that the intestinal mucosa has a unique subset of CD4+ T cells that secrete TGF-beta (Th3 cells) that provide help for IgA. These cells have downregulatory properties for Th1 cells and therefore play an important role in the active suppression of oral tolerance and IgE response. What determines that an individual develops one of these diseases? It is now clear that these different pathological entities are multifactorial. Different environmental factors and a complex genetic predisposition where more that one gene and more than one chromosome are involved. The extent and severity of the inflammatory response depends on the genetic diversity of the bacteria or the amount of the antigen on the one hand and on the genetic constitution of the host on the other. The abnormal immune response in the human gut is predominantly a Th1-like inflammatory response. This can be elicited by bacteria, peptides, possibly the bacterial flora and some viruses. The recent findings in the pathogenesis of the intestinal inflammatory response will probably alter the therapy of the future.

Food allergy, coeliac disease and chronic inflammatory bowel disease in man

It is often stated that the gastrointestinal tract has a limited number of responses to pathogens. Entirely different agents can produce a similar histopathological reaction. However, the expression of the disease in man is very heterogeneous, it varies with the age of the subject and is to a certain extent genetically determined. For example, food allergy is frequent in childhood and not common in adulthood. The intestinal mucosa in the child with cows milk allergy shows a 'flat' mucosa, which may be indistinguishable of that observed in gluten sensitive enteropathy or coeliac disease. Subjects with other forms of food allergy may have a morphologically normal small intestinal mucosa, occasionally with increased IgE plasma cells and often only characterised by an increased intestinal permeability. An abnormal intestinal permeability is one of the hallmarks of an inflamed gut, however, subjects with a latent form of coeliac disease have an abnormal permeability only without overt signs of inflammation. Recently, it has become clear that what determines the characteristics of the intestinal inflammatory response is dependent on the cytokines involved during the response and this seems to be the same in the stomach, the small intestine and the colon. A so-called Th1 response, with an increased production of IFN-gamma, TNF-alpha and other pro-inflammatory cytokines, occurs in the stomach when infected by Helicobacter pylori, in the small intestine when the subject with coeliac disease consumes normal bread and during the active phases of Crohn's disease. A Th2 response is characteristic of the allergic subject and there is some evidence that it is the predominant response in subjects with ulcerative colitis. We still do not know the fine-tuning of the cytokine response but IL-12 appears to be a key cytokine in polarising the response to a Th1 type. More recently it has become clear that the intestinal mucosa has a unique subset of CD4+ T cells that secrete TGF-beta (Th3 cells) that provide help for IgA. These cells have downregulatory properties for Th1 cells and therefore play an important role in the active suppression of oral tolerance and IgE response. What determines that an individual develops one of these diseases? It is now clear that these different pathological entities are multifactorial. Different environmental factors and a complex genetic predisposition where more that one gene and more than one chromosome are involved. The extent and severity of the inflammatory response depends on the genetic diversity of the bacteria or the amount of the antigen on the one hand and on the genetic constitution of the host on the other. The abnormal immune response in the human gut is predominantly a Th1-like inflammatory response. This can be elicited by bacteria, peptides, possibly the bacterial flora and some viruses. The recent findings in the pathogenesis of the intestinal inflammatory response will probably alter the therapy of the future.

Advances in the immunogenetics of coeliac disease. Clues for understanding the pathogenesis and disease heterogeneity

Recent studies using the technique of the human genome screening in families with multiple siblings suffering from coeliac disease have suggested the presence of at least four different chromosomes in the predisposition to suffer from coeliac disease. Two loci in chromosome 6 appear to be important in disease susceptibility. Other studies based on cytokine gene polymorphisms have found a strong association with a particular haplotype in the TNF locus. This haplotype carries a gene for a high secretor phenotype of TNFalpha. The finding may be important in understanding the heterogeneity of inflammatory response. Evidence has been presented in favour of a predominantly Th1 pattern of cytokine production by the coeliac disease associated HLA-DQ restricted T cell clones. HLA-DQ2 and -DQ8 restricted gliadin-specific T cells have been shown to produce IFN-gamma, which appears to be an indispensable cytokine in the damage to enterocytes encountered in the small intestine, since the histological changes can be blocked by anti-IFN-gamma antibodies in vitro. TNF-alpha, also produced by several T cell clones, may in conjunction with IFN-gamma have a toxic effect or enhance the IFN-gamma-induced increase of HLA-class II expression on surface enterocytes. In the lamina propria this leads to an increased expression of adhesion molecules such as ICAM-1 on T lymphocytes and macrophages. Th1 cells also activate cytotoxic CD8+ T cells that migrate in the epithelial layer, and stimulate further LPL macrophages to produce IFN-gamma and TNF-alpha enhancing the inflammatory response. During this process autoreactive T cells proliferate, creating a situation which is very similar to the process that takes place in autoimmune diseases. Occasionally, this inflammatory destruction of the small intestinal integrity initiated by gluten peptides goes further and develops into a proper autoimmune disease which requires the use of immunosuppressive drugs in addition to a gluten-free diet.

Genetics of inflammatory bowel disease: implications for the future

There is overwhelming evidence that genetic factors play a role in the predisposition to suffer the development of the chronic inflammatory bowel diseases. The genetic analysis of complex diseases, such as ulcerative colitis and Crohn's disease, is difficult. The presence of disease heterogeneity, the relative low frequency in the population, the degree to which first-degree relatives are affected (approximately 10%), the presence of genes with minor genetic effects, and ethnic differences are some of the difficulties encountered when identifying disease susceptibility loci. Two major approaches to identifying these genes are being followed at present. The first, family-based, consists of studying linkage analysis in sibling pairs and parental transmission in genome-wide screening using microsatellite markers. These studies are appropriate and helpful for finding genes of major or moderate effects but may provide difficulty when identifying genes with minor effects. Risch and Merikangas have pointed to the power of association studies utilizing candidate genes in families. These studies should be considered in the future in genome-wide screens when technologic advances permit. The second approach is based on classic epidemiologic designs, population-based studies, using candidate genes in the framework of a biologic hypothesis. Recent data using both approaches in both Crohn's disease and ulcerative colitis are reviewed. The results of genome-wide linkage studies have not reached consensus but suggest that these diseases are different and polygenic in nature. We have started our studies with the hypothesis that an abnormal immune dysbalance contributes to the biologic basis of disease. We therefore study polymorphisms in genes encoding proinflammatory and regulatory cytokines. Preliminary data of these association studies suggest the importance of several genes with small effects in determining the severity and prognosis of these diseases.

Combined effect of HLA-DRB1*1501 and interleukin-1 receptor antagonist gene allele 2 in susceptibility to relapsing/remitting multiple sclerosis

Susceptibility to multiple sclerosis (MS) is associated with HLA-DRB1*1501. Many reports have suggested associations with other loci but these results remain unconfirmed. We studied the IL-1 receptor antagonist (IL-1ra) gene polymorphism and the HLA-DR and DQ allele frequencies by DNA-based methods in both the primary chronic progressive form (PP MS) and the relapsing/remitting form (R/R MS). The frequency of DRB1*1501 and IL-1ra allele 2 were significantly higher in R/R MS. Association was more marked in the female sex and in patients with benign forms of R/R MS. On the other hand DR4 subtypes carrying a Val at position 86 in the DR beta chain were increased in PP MS. The present study indicates that MS is genetically heterogeneous and shows a combined effect of HLA-DR and IL-1ra genes in susceptibility to the R/R form of the disease.

Evidence for genetic heterogeneity in inflammatory bowel disease (IBD); HLA genes in the predisposition to suffer from ulcerative colitis (UC) and Crohn's disease (CD)

Family and epidemiological studies support a genetic susceptibility to UC and CD. Conflicting reports regarding associations between UC and HLA-DR2 and between CD and various HLA alleles have been published. The aim of this study was to determine whether molecularly defined HLA-DR genes are associated with these diseases in a Dutch group of patients. Fifty-nine unrelated Dutch UC patients and 89 CD patients were typed using DNA-based methods. A total of 2400 healthy local blood donors served as controls. The phenotype frequency of the HLA-DRB1*15 allele was increased in UC patients compared with controls (42% versus 26% in controls; P = 0.006; odds ratio (OR) = 2.1), and was predominantly found in female patients (53% versus 24%; P = 0.001; OR = 3.5). The DRB1*15 allele was increased in UC patients having a positive family history (P = 0.01; OR = 5.8). Among the 16 patients who showed an increase in extent of disease during follow up, 10 were DRB1*15+ (P = 0.002; OR = 4.8). The frequency of the DRB1*13 allele was decreased in patients with UC (15% versus 28% in controls; P = 0.04; OR = 0.5). In CD, no association was observed between disease or particular clinical subgroups and any allele tested. The present study provides additional evidence for the genetic association between UC and HLA-DRB1*15, and supports recent findings that the susceptibility gene(s) for CD is not located in the HLA class II region.

TNF-alpha promoter polymorphisms, production and susceptibility to multiple sclerosis in different groups of patients

TNF-alpha production in whole blood cultures upon stimulation with LPS was determined in 179 individuals from 61 families in order to characterise the magnitude of inherited differences in TNF-alpha production. The three families characterised by highest TNF production showed 7.1 +/- 0.3 ng TNF/ml upon culture with 10 ng LPS and 10.2 +/- 0.2 ng TNF/ml upon culture with 1000 ng LPS. in contrast to the three families characterised by the lowest TNF production that showed a production of 1.6 +/- 0.1 ng TNF upon culture with 10 ng and 2.5 +/- 0.2 ng/ml upon culture with 1000 ng LPS/ml. This difference could not be attributed to the promoter polymorphisms -308 G to A. -238 G to A or -376 G to A, although the -238 GA donors produced 2.1 +/- 0.9 ng TNF upon culture with 10 ng endotoxin compared to 3.2 +/- 2.2 ng TNF for the -238 GG donors. In line with these results the frequency of the -238 GG genotype was increased in hospitalized MS patients in a nursing home (100% 238GG, n = 57) compared to MS patients in an outpatient's clinic (94% 238GG, n = 98) or Dutch controls (90% 238GG, n = 180). These results suggest that the -238 GG genotype is differently distributed in hospitalized MS patients in a nursing home.

Secretion of tumour necrosis factor alpha and lymphotoxin alpha in relation to polymorphisms in the TNF genes and HLA-DR alleles. Relevance for inflammatory bowel disease

The genes for tumour necrosis factor alpha (TNF alpha) and lymphotoxin alpha (LT alpha; TNF beta) are tandemly arranged in the central region of the MHC. They may, therefore, be of importance for the aetiology of MHC-associated diseases. The authors have prospectively studied the secretion of TNF alpha and LT alpha in relation to polymorphisms at positions -308 and -238 in the TNF alpha gene (TNFA), and two polymorphisms in the first intron of the LT alpha gene (LTA), as well as HLA-DR in 30 patients with chronic inflammatory bowel diseases (IBD) and 12 healthy controls. In the Dutch population, the alleles of these four polymorphisms are present in only five combinations, called TNF-haplotypes: TNF-C, -E, -H, -I, and -P. Significant associations between TNF haplotypes and TNF alpha and LT alpha secretion were found when PBMC were cultured with T-cell activators, irrespective of disease. Mean TNF alpha secretion of individuals carrying the HLA-DR3 associated TNF-E haplotype was significantly higher, as compared to individuals without this haplotype (26 441 pg/ml versus 19 629 pg/ml; P = 0.014). Individuals carrying the TNF-C haplotype produced the lowest amount of TNF alpha (17 408 pg/ml; P=0.022). The TNF-C and TNF-E haplotypes differ only at position -308 in the promoter of TNFA. Individuals carrying the HLA-DR1 associated TNF-I haplotype produced significantly less LT alpha when compared to those who lack this haplotype (1979 pg/ml versus 3462 pg/ml; P = 0.006). As the TNF-I haplotype is also associated with low TNF alpha secretion, this haplotype thus defines a 'low secretor phenotype'. In conclusion, this is the first study to show associations between TNF haplotypes and TNF alpha and LT alpha secretion when T-cell stimulators are used. These findings will contribute to define disease heterogeneity in IBD and may be of relevance for understanding the pathogenesis of autoimmune diseases.

Distribution of four polymorphisms in the tumour necrosis factor (TNF) genes in patients with inflammatory bowel disease (IBD)

In 153 patients with IBD, 64 with Crohn's disease (CD), and 89 with ulcerative colitis (UC), as well as in 54 healthy controls (HC), the frequencies of four known di-allelic polymorphisms in the genes for TNF-alpha and lymphotoxin alpha (LTalpha) were investigated. In the Dutch population, the alleles of these four polymorphisms are present in only five combinations, called TNF haplotypes: TNF-C, -E, -H, -I, -P. Furthermore, the relation with the presence of perinuclear anti-neutrophil cytoplasmic autoantibodies (P-ANCA) was studied. A small, but statistically significant, association between the polymorphism at position -308 in the promoter region of the TNF-alpha gene and UC was found. The frequency of the uncommon TNF-alpha -308 allele 2 was found to be decreased in patients with UC compared with HC (allele frequency of allele 2 in UC patients 0-15 versus 0.25 in HC, P=0.044). No significant differences in distribution of the TNF haplotypes were found between IBD patients and HC, although there was a tendency towards a higher frequency of the TNF-C haplotype in UC patients compared with controls (haplotype frequency 22% versus 13%; P=0.19). No statistically significant differences in distribution of the TNF haplotypes were observed between P-ANCA-positive and P-ANCA-negative UC patients. The strength of the associations indicates that TNF genes are not markers for the predisposition to suffer from IBD. They may, however, be markers of subsets of patients with UC and CD.

Evidence of genetic heterogeneity in IBD: 1. The interleukin-1 receptor antagonist in the predisposition to suffer from ulcerative colitis

OBJECTIVE

To investigate a polymorphism within intron 2 of the interleukin-1 receptor antagonist (IL-1ra) gene in a Dutch white population of patients with ulcerative colitis and Crohn's disease.

DESIGN

Genotype and allele frequencies of the polymorphic region in the IL-1ra gene were determined in 111 unrelated patients with ulcerative colitis, 92 patients with Crohn's disease, and 86 healthy controls.

METHODS

The polymorphic region on the IL-1ra gene was amplified by the polymerase chain reaction (PCR). The resultant products were analyzed by electrophoresis on 2% agarose gels and stained with ethidium bromide. Amplification of the second exon of HLA-DRB1, HLA-DQA1, and HLA-DQB1 genes was performed by PCR, and Dot-blot analysis with biotin-labelled sequence-specific oligonucleotide probes was used for HLA typing. The standard perinuclear antineutrophil cytoplasmic antibodies (pANCA) indirect immunofluorescence assay was performed according to the protocol described by the First International Workshop on ANCA.

RESULTS

The frequency of allele 2 of the IL-1ra gene in ulcerative colitis (27.0%) and Crohn's disease patients (25.5%) did not differ significantly from healthy controls (23.8%). However, the estimate of the relative risk for carriers of allele 2 for ulcerative colitis [odds ratio (OR): 1.35, 95%-confidence interval (CI) from 0.73 to 2.49] was in agreement with a previous British study. The exact test for homogeneity of odds ratios provided no evidence for heterogeneity between both populations (P = 0.35) and therefore confirmed the genetic associated between ulcerative colitis and the IL-1ra allele 2 in a different population. Our data confirm that, in ulcerative colitis, the presence of this allele is a genetic marker for severity of the disease. A significant association was demonstrated between the carriership of allele 2 of the IL-1ra gene and the trend over the three localizations in ulcerative colitis (P = 0.023). The same approach for Crohn's disease when compared with healthy controls did not provide evidence for a similar association. The meta-analysis, based on the British data and our data, yielded: OR = 1.06, 95%-CI from 0.71 to 1.59, and P = 0.767. No association between IL-1ra gene polymorphism, and pANCA and the HLA-DR2 allele was found in ulcerative colitis.

Allelic polymorphism in IL-1 beta and IL-1 receptor antagonist (IL-1Ra) genes in inflammatory bowel disease

Recent reports have shown that allele 2 of the IL-1 receptor antagonist (IL-1Ra) gene is over-represented in ulcerative colitis (UC). Healthy individuals carrying allele 2 of this gene have increased production of IL-1Ra protein. Since the final outcome of the biological effects of IL-1 beta may depend on the relative proportion of these two cytokines, we have studied if a TaqI polymorphism in the IL-1 beta gene, which is relevant to IL-1 beta protein production, may be involved in the genetic susceptibility to UC and Crohn's disease (CD), in association with the established IL-1Ra gene polymorphism. Polymorphisms in the closely linked genes for IL-1 beta and IL-1Ra were typed in 100 unrelated Dutch patients with UC, 79 with CD, and 71 healthy controls. The polymorphic regions in exon 5 of the IL-1 beta gene and in intron 2 of the IL-1Ra gene, were studied by polymerase chain reaction (PCR)-based methods. The IL-1 beta allele frequencies in UC and CD patients did not differ from those in healthy controls. In order to study if the IL-1 beta gene polymorphism might participate synergistically with the IL-1Ra gene polymorphism in susceptibility to UC and CD, individuals were distributed into carriers and non-carriers of allele 2 of the genes encoding IL-1 beta and IL-1Ra, in each of the patient groups and controls. Results indicated a significant association of this pair of genes, estimated by the odds ratio (OR) after performing Fisher's exact test, in the UC group (P = 0.023, OR = 2.81), as well as in the CD group (P = 0.01, OR = 3.79). Thus, non-carriers of IL-1 beta allele 2 were more often present in the subgroup of patients carrying the IL-1Ra allele 2. By contrast, no association of these alleles was detected in the group of healthy controls (P = 1.00, OR = 0.92). These results suggest that the IL-1 beta/IL-1Ra allelic cluster may participate in defining the biological basis of predisposition to chronic inflammatory bowel diseases.

Absence of pepsinogen A3 gene expression in the gastric mucosa of patients with gastric cancer

AIMS

To investigate the expression of pepsinogen A3 (Pg3) encoding genes in the gastric mucosa of normal controls and subjects with atrophic gastritis and gastric cancer.

METHODS

One hundred and fifty nine patients underwent upper gastrointestinal endoscopy with sampling of gastric biopsy specimens and serum. Pg3 isoproteins were determined by electrophoresis in serum and gastric mucosal biopsy specimens. Pg3 encoding genes were assessed by PCR in DNA obtained from peripheral blood.

RESULTS

One hundred and one subjects (82 normal histology/chronic gastritis, 17 atrophic gastritis, two gastric cancer) showed a pepsinogen phenotype with presence of Pg3 and a corresponding pepsinogen genotype with presence of Pg3 encoding genes. Fifty eight subjects showed a phenotype lacking Pg3. In 39 of them (23 normal histology/chronic gastritis, 11 atrophic gastritis, five gastric cancer), a corresponding genotype without Pg3 encoding genes was found. However, in the remaining 19 subjects (4 normal histology/chronic gastritis, nine atrophic gastritis, six gastric cancer); Pg3 encoding genes were demonstrable in the absence of Pg3 production.

CONCLUSIONS

Unexpressed Pg3 encoding genes can be shown in many cases of atrophic gastritis and gastric cancer, but rarely in healthy controls and subjects with superficial gastritis. The correlation of atrophic gastritis and gastric cancer with a pepsinogen phenotype lacking Pg3 can be explained by loss of expression of Pg3 encoding genes throughout the complete gastric mucosa. The mechanism of such loss and the importance as a marker for premalignant degeneration have to be elucidated.

The renal handling of pepsinogen A isozymogens in man

Pepsinogen A (PGA) isozymogens are low molecular weight proteins that are present in serum and urine. The differences in the molecular structure of PGA-isozymogens involve only 2-4 amino acid substitutions. In a previous study, performed in 13 subjects only, a remarkable difference between the fractional renal clearances of the main PGA-isozymogens (PGA-3, PGA-4 and PGA-5) has been demonstrated. The aim of the present study was to further investigate these differences in fractional clearance between PGA-isozymogens and to determine whether these differences are caused by differences in glomerular sieving. For this purpose the fractional clearances of PGA-isozymogens were measured in 57 subjects. In accordance with the previous study, the median fractional clearance of PGA-5 (13%) was lower than the median fractional clearance of PGA-4 (17%; p < 0.02) and the median fractional clearance of PGA-4 was lower than the median fractional clearance of PGA-3 (26%; p < 0.001). The glomerular sieving coefficients of PGA-isozymogens were measured in 11 subjects during an elective heart catheterization by means of the fractional renal extraction method. No significant difference between the glomerular sieving coefficients of PGA-isozymogens could be demonstrated, being 0.81 for PGA-3, 0.96 for PGA-4 and 0.84 for PGA-5. It is concluded that the differences in renal handling between PGA-isozymogens must be explained by differences in tubular reabsorption. These differences in tubular reabsorption between PGA-isozymogens support the hypothesis that positively charged amino acid residues of proteins are involved in the tubular protein reabsorption.

Tubular reabsorption of pepsinogen isozymogens in man studied by the inhibition of tubular protein reabsorption with dibasic amino acids

1. The fractional clearances of pepsinogen A (PGA), pepsinogen C (PGC) and the main PGA isozymogens, i.e. PGA-3, PGA-4 and PGA-5, were measured in 13 healthy male volunteers before and during blockade of tubular protein reabsorption by intravenous infusion of either L-arginine hydrochloride (n = 8; 0.5 g h-1 kg-1 body weight) or an equimolar amount of L-lysine hydrochloride (n = 5; 0.44 g h-1 kg-1 body weight). Glomerular filtration rate was measured by a radioisotope method. 2. The fractional baseline clearance of PGC (1 +/- 1%) was lower than that of PGA (20 +/- 10%). In addition, the fractional clearance of the PGA isozymogens appeared to be different: the fractional clearance of PGA-5 (7 +/- 3%) was lower than that of PGA-4 (18 +/- 9%), and the fractional clearance of PGA-4 was lower than that of PGA-3 (30 +/- 10%). These differences in fractional clearance between PGA isozymogens decreased during infusion of both arginine and lysine. 3. Pepsinogens are freely filtered proteins. It can therefore be concluded that the differences in fractional clearance between PGA isozymogens imply differences in tubular reabsorption. This is remarkable as PGA isozymogens are proteins with an almost identical amino acid sequence and electric charge. The disappearance of the differences in tubular reabsorption during arginine and lysine infusion suggests that PGA isozymogens differ in affinity for negatively charged binding sites in the tubular cell membrane. In order to explain the low fractional clearance of PGC compared with that of PGA and the less marked effect of arginine or lysine infusion on the fractional clearance of PGC, an additional PGC-specific binding site has to be postulated.