No evidence for involvement of the interleukin-10 -592 promoter polymorphism in genetic susceptibility to primary biliary cirrhosis

IL-6 and IL-10 gene polymorphisms and cirrhosis of liver risk from a comprehensive analysis

BACKGROUND

Different inflammatory and immune cytokines play a key role in the development of cirrhosis of liver (CL). To investigate the association between interleukin-6,10 (IL-6,10) genes polymorphisms and CL risk through comparison of the allele and genotype distribution frequencies by meta-analysis.

METHODS

A literature search covered with the PubMed, Embase, Cochrane Library, Web of Science, Google Scholar, SinoMed (CNKI and Wanfang) through 20th April, 2021. Odds ratios (OR) and 95% confidence intervals (CI) were used to assess the strength of associations.

RESULTS

After a comprehensive search, three common polymorphisms (rs1800872, rs1800871, rs1800896) in IL-10 gene were selected, and three common polymorphisms (rs1800795, rs1800796, rs1800797) in IL-6 gene were also identified. The important finding was that IL-10 rs1800872 was a risk factor for CL development. For example, there has a significantly increased relationship between rs1800872 polymorphism and CL both in the whole group (OR: 1.30, 95%CI: 1.01-1.67 in heterozygote model), Asian population (OR: 1.40, 95%CI: 1.03-1.88 in heterozygote model) and hospital-based source of control (OR: 1.40, 95%CI: 1.01-1.96 in dominant model). In addition, significant association was found between rs1800896 and primary biliary cirrhosis subtype disease (OR: 1.30, 95%CI: 1.01-1.68 in allelic contrast model). No association was observed in all three polymorphisms in IL-6 gene.

CONCLUSION

Our present study suggests that the IL-10 rs1800872 and rs1800896 polymorphisms is potentially associated with the risk of CL susceptibility.

Meta-Analysis of the Relation Between IL10 Promoter Polymorphisms and Autoimmune Liver Disease Risk

BACKGROUND

Single nucleotide polymorphisms of the IL10 gene have been linked to the occurrence of autoimmune liver disease.

METHODS

We performed a meta-analysis to assess the association between three IL10 promoter polymorphisms (rs1800896, rs1800871, and rs1800872) and the risk of autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis.

RESULTS

In total, 1420 articles were initially identified through database retrieval. After screening, seven eligible articles were ultimately included in the meta-analysis. A fixed-effect model was used for all Mantel-Haenszel statistics due to the absence of large between-study heterogeneity (all I² < 50%, p > 0.1). No association between any of the studied polymorphisms and risk of autoimmune liver disease was detected in the allele, homozygote, heterozygote, dominant, recessive, or carrier genetic models (p_association > 0.05). Potential publication bias was excluded using Begg's and Egger's tests. Similar negative results were observed in subgroup analyses and in an analysis of the three haplotypes of rs1800896/rs1800871/rs1800872 (G/C/C, A/C/C, and A/T/A).

CONCLUSION

Our meta-analysis strongly suggests that the IL10 rs1800896, rs1800871, and rs1800872 polymorphisms are not associated with the risk of autoimmune liver disease.

Herb-induced autoimmune-like hepatitis in C57BL/6J mice

BACKGROUND & AIMS

Animal model suitable for studying herb-induced experimental autoimmune hepatitis (AIH) remains a challenging problem. A medicinal herb containing Scutellaria baicalensis Georgi (Sb) and Bupleurum chinense DC (Bc) has been sporadically reported to be related to liver fibrosis. The aim of this study was to investigate the effects of Sb and Bc on experimental AIH in mice.

METHODS

C57BL/6J mice received intraperitoneal injection of Sb and/or Bc herbal extracts (1 mg/kg) for 4 or 8 weeks. Serum samples were collected to analyse serum transferase (AST, ALT), creatinine, markers for AIH and hepatic cytokine levels such as IFN-γ, IL10 and TGF-β1. Peripheral mononuclear cell (PBMC) gene expression profiles were analysed to show their effects on immune system.

RESULTS

Our results showed that Sb or Bc treatment increased serum AST, ALT, IgG and ANA levels. Prominent necroinflammatory changes were demonstrated in the livers of Sb- or Bc-treated mice while the decrease in IFN-γ and elevation of IL10 and TGF-β1 levels in liver tissues. Furthermore, the PMBC gene expression profile suggested that Sb or Bc treatment could modulate immune responses.

CONCLUSION

We conclude that the presence of AIH in Sb- or Bc-treated mice and C57BL/6J strain mice is a reliable animal model for studying herb-induced AIH-like hepatitis.

HLA-DR polymorphism and primary biliary cirrhosis: evidence from a meta-analysis

BACKGROUND AND AIMS

We undertook this study to review and quantitatively analyze the association between human leukocyte antigen (HLA) DR polymorphisms and susceptibility of primary biliary cirrhosis (PBC).

METHODS

All relevant publications on the association between HLA-DR polymorphisms and PBC were searched through June 2013. Odds ratios (OR) and confidence intervals (CI) for the comparisons between case and control group were calculated. Statistical analysis was performed using Stata 11.0 software.

RESULTS

Nineteen articles (or 20 studies including the substudies) were identified. For DR*7 allele, the ORs (95% CIs) were 1.530 (1.310, 1.788), 1.757 (1.285, 2.403) and 1.495 (1.211, 1.845) in overall, Asian and European populations, respectively. For DR*8 alleles, the ORs (95% CIs) were 3.158 (1.822, 5.475), 2.803 (2.420, 3.247) and 3.056 (2.573, 3.629) in Asian, American and European subgroups, respectively. The subgroup analysis for DR*11 and DR*13 showed a significant association in Asian and European population. For DR*12 and *15 alleles, the overall ORs (95% CIs) were 0.551 (0.404, 0.753) and 0.721 (0.607, 0.857). However, in subgroup analysis for DR*12 allele, the association was only found in Asian population. In addition, statistical significance exists in American and European populations in the subgroup analysis for DR*15 allele.

CONCLUSION

Our meta-analysis suggested that HLA-DR *7 and *8 allele polymorphisms contributed to the susceptibility of PBC, whereas DR*11, *12, *13 and *15 allele polymorphisms are protective factors in certain population.

Genetic susceptibility to different clinical forms of tuberculosis in the Peruvian population

Racial variation, twin studies, segregation analyses, linkage and association studies all suggest that genetic factors play an important role in predisposition to tuberculosis. Many previous studies have been performed with pulmonary TB patients, as the most prevalent form of clinical TB (nearly 95%), and very few of them have considered extrapulmonary TB. The present study evaluates the effects of variation in eight candidate genes (LTA, TNF, IL1B, IL1RN, IL10, TGFB1, TIRAP and P2X7) with pulmonary, pleural, miliary and other extrapulmonary forms of TB in a Peruvian population from the North of Lima. 626 TB cases and 513 healthy controls were enrolled in this study. LTA(+368) and IL10(-592) were associated with different clinical forms of TB (P<0.05). LTA(+368) genotype A/A was protective for pleural TB, LTA(+368) G/A was correlated with susceptibility to miliary TB. Genotypes A/A and G/A were associated with protection and susceptibility respectively when considering all extrapulmonary TB forms versus either healthy controls or pulmonary TB patients. Carriers of IL10(-592)*C were under-represented among those with pulmonary TB and all TB forms (P<0.001). IL10(-1082)-IL10(-592) haplotypes showed different distributions among patients with pulmonary TB and all TB forms (P<0.01) when compared to healthy controls. In addition, IL10(-1082)-IL10(-592) haplotypes showed differences between pleural, miliary and all forms of extrapulmonary TB when compared with pulmonary TB (P<0.05). All findings are consistent with an under-representation of the IL10(-1082)*A-IL10(-592)*A haplotype in pulmonary TB patients. These results suggest that the polymorphisms LTA(+368) and IL10(-592), or variants in strong linkage disequilibrium, variably affect susceptibility to the differing clinical forms of TB in Peruvians.

Genetic background of primary biliary cirrhosis

The clustering of patients in a representative family as well as relatively high concordance rate in monozygotic twins strongly indicate that genetic factors play a crucial role in modulating primary biliary cirrhosis (PBC) by conferring susceptibility to, or providing protection from, the disease. Therefore, much like other autoimmune diseases, intensive investigations have attempted to elucidate which genes are incriminated in the etiology of PBC. So far, a number of genes, including major histocompatibility complex (MHC) class I and II, cytokines and cell surface molecules, have been examined to seek the possibility of whether single nucleotide polymorphisms (SNP) of the gene might be associated with susceptibility to PBC. Nevertheless, it appears that methodologicaldifficulties, mainly the limitation of the number of individuals tested in each study, hamper the detection of a convincing and reproducible link between genetic polymorphisms and the etiology of PBC. Also, the difference in genetic background among several ethnic groups may play a role in concealing the association. In this review, I will highlight the genetic association in PBC, and review the association of genetic polymorphisms with the etiology of PBC, which have been reported in various ethnicities.

Genetic background of the multifactorial liver and bile duct diseases

The majority of liver diseases, are complex. They are the results of interactions between several genes and environmental factors. Familial aggregation and higher concordance rate of monozygotic twins compared to those of dizygotic twins provide evidence for the importance of genetic factors in the pathogenesis. There are only limited data in connection with the genetic background of multifactorial liver diseases. In the future, the genetic background may permit prevention, early, accurate diagnosis, prediction of disease course, complications, prognosis, as well as treatment response.

Genes and (auto)immunity in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic autoimmune cholestatic liver disease most commonly encountered in postmenopausal women; it is characterized by high-titer serum autoantibodies to mitochondrial antigens, elevated serum IgM, progressive destruction of intrahepatic bile ducts, and ultimately liver cirrhosis and failure. The cytopathic mechanisms leading to the selective destruction of intrahepatic cholangiocytes are still largely unknown. The current theory on the pathogenesis of PBC indicated that environmental factors might trigger autoimmunity in genetically susceptible individuals. In fact, genetic predisposition is critical to disease onset and progression, yet peculiar among autoimmune diseases, as indicated by the lack of a strong association with major histocompatibility complex haplotypes. Further, the recently reported concordance rate among monozygotic twins strengthens the importance of genetic factors, while also indicating that additional factors, possibly infectious agents or xenobiotics, intervene to trigger the disease. In this review, the available data regarding the genetic factors associated with PBC susceptibility and progression, as well as the available evidence regarding the immunomediated pathogenesis of PBC, will be critically illustrated and discussed.

From bases to basis: linking genetics to causation in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a multifactorial autoimmune disease with inherited and environmental components in pathogenesis. It is exceptional among autoimmune diseases in showing strong heritability according to familial occurrence and monozygotic twins concordance, yet with weak associations with the usual genetic risk elements for autoimmunity, such as the HLA alleles. Among the latter, there is risk (at least in some populations) conferred by HLA DRB1*08 and possibly some protection by DRB1*11. However, the inconsistency among studies on HLA is surprising, given that PBC is a relatively homogenous disease entity. Among non-HLA genes, some studies implicate polymorphisms of genes for cytotoxic T-lymphocyte antigen-4, interleukin-2, or interleukin-10; polymorphisms of the vitamin D receptor could synergize with low sunlight exposure to create deficiency of the immunoregulatory factor, activated vitamin D. A new lead is available from the finding in female subjects with PBC of an increase in the degree of monosomy of the X chromosome that is presumed to carry immune response genes. A further suggested source of inquiry is the apparent protection of African-American women from PBC. Finally, data on inheritance should be sought in PBC by descent methodology, rather than by cross-sectional association studies in cases and control subjects, and based on analysis of a large number of families with an affected member through a worldwide effort.

Genetic factors in the pathogenesis of primary biliary cirrhosis

Current knowledge of the genetic basis of PBC is at best incomplete and at worst poor. Studies so far may be used as a guide to the pitfalls that await unwary investigators and also in deciding where to look and which genes or systems are most likely to yield informative results. The Human Genome Project has revealed a vast array of polymorphism that is too much to contemplate even with the best of current techniques. The crucial processes are the selection of candidates and study design. The strong genetic associations so far in PBC are with chromosomes 6p21.3 and 2q and include; HLA DRBI*08 haplotypes, CTLA4* G and IL1RN-IL1B haplotypes, CASP8, and nramp1. Many of the latter should be considered with caution until confirmed in independent series. Other associations with MBL, APOE and VDR remain to be confirmed. There are also several informative negatives, MMP3 and IL10 for example. It is unlikely that the only genes that influence disease susceptibility and progression in PBC are immunoregulatory genes concerned with T cell immunity. Recent studies indicate a new era for immunogenetics, when genes encoding all immune active proteins may be considered as candidates. One should not concentrate solely on the immune response as recent investigations of mannose binding lectin and apolipoprotein-E testify. One is only just beginning to understand the genetic basis of complex diseases like PBC. The key issues for future investigators are: defining the mechanisms where by self tolerance is broken, defining the mechanisms that determine the rate of disease progression, and identifying genetic markers to predict progression and malignancy. Assessing the genetic basis of variability in disease progression. The significant variation in rate of progression of PBC has led to the hypothesis that genes, in addition to contributing to disease susceptibility, may also determine the rate of disease progression. Several of the studies mentioned earlier have suggested associations between alleles at polymorphic loci and rate of progression . All studies performed to date, however, have been retrospective in nature. One problem inherent in such studies is that of definition of disease progression. One simple definition, that of histological progression to Scheuer stage IV disease , requires liver biopsy. The need to perform repeat biopsies raises ethical problems in cases where there is no other clinical indication. Studies of histologic progression in patients in the control arm of therapeutic trials represent one scenario where repeat biopsy would be indicated. However, the typical time course of such trials is 2 years, insufficient for meaningful assessment of disease progression and natural history, particularly in PBC where there is marked heterogeneity and, as a result, tissue sampling error. Yet, alternative systems for assessing disease progression, such as the Mayo prognostic score, lack sensitivity in any scenario other than existing advanced disease. Outlook for the future. Clinical observations support a significant genetic component to disease susceptibility. Elucidating predisposing genetic associations will markedly assist in understanding the pathophysiology of disease. Investigations to date have been restricted to various community-based case-control association studies, with well-recognized limitations. In future SNP maps and haplotype maps from the Human Genome Project will be available. Studies will require the collection of several well-characterized patients. To meet the required statistical power this will necessitate collaboration on a national and international scale. It is essential that these studies address the relationship between genes and disease progression. The possibility of identifying, in the early stages of disease, patients who are at elevated risk for more rapid progression, would have obvious clinical benefit in terms of patient management and therapy.

Epidemiology of autoimmune liver disease

Primary biliary cirrhosis (PBC), autoimmune hepatitis (AIH) and primary sclerosing cholangitis (PSC) are chronic liver diseases that likely have an autoimmune basis to their pathogenesis. Although significant strides have been made in the clinical management of these conditions, their pathogenesis remains obscure. Understanding of various epidemiological factors may shed light on predisposing or causative factors for these diseases. Most is known about the epidemiology of PBC, with only minimal information on that of PSC and AIH. In this review, the current data on the epidemiology of PBC, AIH and PSC are summarized and suggestions are made for future work in this important area.

Genetic effects on susceptibility, clinical expression, and treatment outcome of type 1 autoimmune hepatitis

Currently, three genetic factors have been short-listed as possible modulators of susceptibility and severity in type 1 AIH. They are female sex, HLA DRB alleles encoding lysine at position DR beta 71, and the CTLA4*G allele. The fourth association (i.e., TNFRSF6) remains to be confirmed. There are many other candidates to investigate. Current hypotheses suggest that the autoimmune genotype will include multiple (some linked, others discrete) loci which make a permissive background. Not all "at risk" individuals will develop clinical disease, and selection will depend on the interaction of this "permissive gene pool" (i.e., the host) with the environment. The resulting autoimmune phenotype will depend on gene dose and gene interaction. The human genome project has presented medical science with the challenge to identify the genes that determine common human diseases, including autoimmunity [1]. Although type 1 AIH is considerably less common than diabetes or RA, it may serve as a useful model for other autoimmune diseases. Diagnosis depends on histologic findings, and liver biopsy examinations are part of the usual assessment strategy in type 1 AIH. The availability of these tissue specimens provides a clear basis for monitoring disease progression and may permit investigators to study the impact of genetic polymorphism on disease activity. The emergence of high throughput technologies will significantly enhance our ability to study the interactions between constellations of polymorphic genes and both disease expression and behavior. An abundance of polymorphism is found in the genome. In many diseases, functional studies and genome scanning have helped revise and reduce the list of candidates. Affected families are rare in type 1 AIH, and patients are at risk if corticosteroid treatment is withheld. Under these circumstances, genetic studies may be the most practical, low risk means to investigate the pathogenesis of type 1 AIH and many other autoimmune diseases.

Association of the tumour necrosis factor alpha -308 but not the interleukin 10 -627 promoter polymorphism with genetic susceptibility to primary sclerosing cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of unknown aetiology. Abnormalities in immune regulation and genetic associations suggest that PSC is an immune mediated disease. Several polymorphisms within the tumour necrosis factor alpha (TNF-alpha) and interleukin 10 (IL-10) promoter genes have been described which influence expression of these cytokines. This study examines the possible association between polymorphisms at the -308 and -627 positions in the TNF-alpha and IL-10 promoter genes, respectively, and susceptibility to PSC.

METHODS

TNF-alpha -308 genotypes were studied by polymerase chain reaction (PCR) in 160 PSC patients from Norway and the UK compared with 145 ethnically matched controls. IL-10 -627 genotypes were studied by PCR in 90 PSC patients compared with 84 ethnically matched controls.

RESULTS

A total of 16% of Norwegian PSC patients and 12% of British PSC patients were homozygous for the TNF2 allele compared with 3% and 6% of respective controls. The TNF2 allele was present in 60% of PSC patients versus 30% of controls (OR(combined data)=3.2 (95% confidence intervals (CI) 1.8--4.5); p(corr)=10(-5)). The association between the TNF2 allele and susceptibility to PSC was independent of the presence of concurrent inflammatory bowel disease (IBD) in the PSC patients; 61% of PSC patients without IBD had TNF2 compared with 30% of controls (OR(combined data)=3.2 (95% CI 1.2--9.0); p(corr)=0.006 ). There was no difference in the -627 IL-10 polymorphism distributions between patients and controls in either population. The increase in TNF2 allele in PSC patients only occurs in the presence of DRB1*0301 (DR3) and B8. In the combined population data, DRB1*0301 showed a stronger association with susceptibility to PSC than both the TNF2 and B8 alleles (OR(combined data)=3.8, p(corr)=10(-6) v OR(combined data)=3.2, p(corr)=10(-5) v OR(combined data )=3.41, p(corr)=10(-4), respectively).

CONCLUSIONS

This study identified a significant association between possession of the TNF2 allele, a G-->A substitution at position -308 in the TNF-alpha promoter, and susceptibility to PSC. This association was secondary to the association of PSC with the A1-B8-DRB1*0301-DQA1*0501-DQB1*0201 haplotype. No association was found between the IL-10 -627 promoter polymorphism and PSC.

Genetic and familial considerations of primary biliary cirrhosis

The genetic basis of human autoimmune diseases is receiving increasing attention. Primary biliary cirrhosis (PBC) is a model autoimmune disease reflective of other organ-specific autoimmune pathology. PBC is an enigmatic autoimmune disease that predominantly affects women and leads to destruction of intrahepatic bile ducts. The serological hallmark of this disease is characterized by antimitochondrial antibodies that specifically react with the E2 components of 2-oxodehydrogenase enzymes, including PDC-E2. There are no clear major histocompatibility complex associations with the development of PBC, despite the observation that first-degree relations of index patients with PBC have a 4-6% prevalence of development of PBC. This risk factor is comparable or higher than any other human autoimmune disease and suggests that a genome-wide approach towards dissection of genetic associations would lead to valuable new insights. In this review, we place these concepts in perspective and highlight in particular the genetic associations in PBC and the importance of studying siblings with PBC who are concordant for disease.

The interleukin-1 and interleukin-10 gene polymorphisms in primary sclerosing cholangitis: no associations with disease susceptibility/resistance

BACKGROUND/AIMS

Although primary sclerosing cholangitis is believed to be an autoimmune disorder, no tissue-specific auto-antibodies have yet been identified, and the strongest support for an autoimmune aetiology comes from HLA-association studies. Three different HLA haplotypes are associated with susceptibility to the disease and one with protection from it. These HLA haplotypes, however, do not account for all of the disease risk and genes outside the HLA region may also have a role in disease pathogenesis. The aim of this study was to investigate, for the first time, polymorphic genes/sites within the interleukin-1 and interleukin-10 genes in a large well-characterised group of patients.

METHODS

Ninety-six patients and 96 control subjects were studied. A single base-exchange polymorphism at position +3953 in the first exon of the IL-1B gene, a penta-allelic repeat sequence in the IL-1 receptor antagonist gene (IL-1RN) and three single base-exchange polymorphisms at positions -592, -819 and -1082 in the IL-10 gene promoter were determined by standard PCR-based techniques.

RESULTS

Overall, there was no significant difference in the distribution of any of the IL-1B, IL-1RN or IL-10 alleles or genes sequences comparing patients and controls. In addition, there was no difference when the patients were stratified for the presence and absence of the HLA DRB1*0301 (DR3) allele or concurrent inflammatory bowel disease.

CONCLUSION

Neither the IL-1B +3953, IL-1RN microsatellites polymorphisms on chromosome 2q13 nor the IL-10 -592, -819, -1082 promoter gene polymorphisms on chromosome 1q31-32 are associated with susceptibility or resistance to primary sclerosing cholangitis.

Frequency and nature of cytokine gene polymorphisms in type 1 autoimmune hepatitis

Genetic involvement in type 1 autoimmune hepatitis (AIH) is indicated by a marked female preponderance and strong, well-established, human leukocyte antigen (HLA) associations. These associations, however, are not universal and a number of genes outside the major histocompatibility complex may also play a role in susceptibility to type 1 AIH. Prime candidates at present are those polymorphic genes encoding the proinflammatory and immunoregulatory cytokines. The aim of this study was to investigate, for the first time, 2 members of the interleukin-1 (IL-1) family (IL-1B and IL-1RN), 3 polymorphic sites in the interleukin-10 (IL-10) gene promoter (positions -1082, -819, and -592), and 2 polymorphisms in the tumor necrosis factor-alpha (TNF-alpha) promoter (positions -308 and -238) in type 1 AIH. The study was performed on 2 independently collected DNA banks, each with appropriate controls, and throughout the analysis associations described in the first set were confirmed in the second set. Standard polymerase chain reaction (PCR)-based genotyping techniques were used. Overall there were no significant differences in the distributions of the IL-1B and IL-10 alleles, genotypes, or haplotypes in either study set. In contrast we report a significant association between type 1 AIH and TNF*2 (first set: 34% of controls vs. 49% of patients, Pc =.014 and second set: 26% vs. 56%, P =.00008). However, TNF*2 is found in strong linkage disequilibrium with the HLA A1-B8-DR3 haplotype and stratification analysis indicates that the association with TNF*2 is interdependent with HLA DRB1*0301. This is an indication that there is more than one susceptibility allele for type 1 AIH on chromosome 6p21.3.

Cytokine polymorphisms associated with clinical features and treatment outcome in type 1 autoimmune hepatitis

BACKGROUND & AIMS

Polymorphisms that control cytokine production can affect immunoregulation. The frequency and consequences of these polymorphisms in type 1 autoimmune hepatitis were determined.

METHODS

DNA samples from 155 patients and 102 ethnically similar normal individuals were assessed by polymerase chain reaction for polymorphisms of 4 different cytokine-producing genes.

RESULTS

Only genotypes associated with the guanine to adenine substitution at position -308 of the tumor necrosis factor gene occurred more commonly in patients than in normal subjects (56% vs. 26%; P < 0.001). Patients with this polymorphism had the HLA DRB1*0301 allele (81% vs. 10%; P < 0.000001) and A1-B8-DRB1*0301 (66% vs. 0%; P < 0.000001) phenotype more frequently and HLA DRB1*04 alleles less often (24% vs. 67%; P < 0.000001). They also entered remission less commonly (56% vs. 78%; P = 0.01), had treatment failure more often (20% vs. 7%; P = 0.03), and developed cirrhosis more frequently (40% vs. 19%; P = 0.05). These latter differences, however, were not statistically significant by adjusted P value.

CONCLUSIONS

A polymorphism of the tumor necrosis factor gene occurs more commonly in patients with type 1 autoimmune hepatitis than in normal subjects; it is associated with a poorer response to corticosteroids. The polymorphism may be inherited as part of the extended A1-B8-DRB1*0301 haplotype and may affect both disease expression and behavior.

Familial primary biliary cirrhosis reassessed: a geographically-based population study

BACKGROUND/AIMS

Development of primary biliary cirrhosis in the close relatives of patients with the disease has been reported in several series, suggesting a genetic component to disease susceptibility. In this study we set out to calculate, as accurately as possible, the prevalence of familial primary biliary cirrhosis in a geographically-based population. Using local population prevalence data, we have also calculated the first-degree relative, sibling and offspring relative risks of overt primary biliary cirrhosis development.

METHODS

All patients with definite or probable primary biliary cirrhosis in the city of Newcastle-upon-Tyne, England, were identified by an exhaustive case-finding search and were prospectively interviewed by a single investigator. Full details of family pedigree and familial primary biliary cirrhosis history were obtained.

RESULTS

One hundred and seventy-three patients were identified, with 160 participating in the study. Thirteen reported a family history of primary biliary cirrhosis. In three cases, both relative pairs were within the study group. The prevalence of a positive family history of primary biliary cirrhosis was therefore 10/157 (6.4% [95% Confidence Interval 2.6-10.2%]), 8/10 cases occurring in first-degree relatives. The patients had a total of 1118 first-degree relatives (live or dead) and 468 siblings. The first-degree relative prevalence of primary biliary cirrhosis was 0.72% [0.2-1.2%] (siblings 0.41% [-0.2-1.0%]). The offspring prevalence was 1.2% [0.04-2.4%], (2.3% [0.1-4.5%] for daughters). The sibling relative risk (lambda(s)) was 10.5.

CONCLUSIONS

The overall prevalence of definite or probable primary biliary cirrhosis in the first-degree relatives of existing patients is <1%. The risk of disease is not, however, uniform, the highest prevalence being seen in the daughters of patients. Suspicion of disease should therefore be highest in this relative group. The calculated lambda(s) for primary biliary cirrhosis in this geographically-based study is significantly lower than previous estimates from case-note-derived case series, but similar to values seen in other autoimmune diseases.

Tumour necrosis factor-alpha promoter polymorphisms in primary biliary cirrhosis

BACKGROUND/AIMS

The incidence of primary biliary cirrhosis (PBC) is increased in the close relatives of patients, suggesting that genetic factors play a role in disease susceptibility. Decreased in vitro production of tumour necrosis factor (TNF)-alpha has been reported in PBC patients, suggesting a potential aetiological role for this cytokine. The aim of this study was to examine two biallelic polymorphisms in the promoter region of the TNF-alpha gene, which may play a role in the control of TNF-alpha secretion, as candidate susceptibility loci in PBC.

METHODS

The polymorphisms at positions -238 and -308 in the TNF-alpha promoter region were analysed by polymerase chain reaction in 168 unrelated PBC patients and 145 local unrelated, geographically matched normal individuals. All PBC subjects were also genotyped for HLA DR8, a previously identified susceptibility locus in PBC.

RESULTS

The -308 TNF1/TNF1 genotype was seen in a similar proportion of PBC patients (66%) and controls (60%). However, this genotype was found significantly more frequently in the 95 PBC patients with more advanced disease (histological stage III/IV) (77%) than in either controls (p<0.01, OR = 2.2 [1.2-4.0]) or the PBC patients with earlier disease (38/73 (52%), p = 0.001 OR 3.1 [1.6-5.9]). Linkage between TNF -308 and HLA DR8 was not seen. No association was found between PBC and the biallelic -238 TNF-alpha polymorphism, either in the whole PBC population or the histological Stage III/IV subgroup.

CONCLUSIONS

Our study provides no evidence for involvement of the TNF-alpha -308 or -238 promoter polymorphisms in genetic predisposition to PBC. However, the significantly increased frequency of the -308 TNF1/TNF1 genotype seen in 95 patients with more advanced disease raises the possibility that this allele may be linked to disease progression rather than susceptibility. The finding of different allele frequencies in PBC patients in different disease subgroups emphasises the importance of clinical phenotype/casemix in the design of disease association studies.