Genetic association of coeliac disease susceptibility to polymorphisms in the ICOS gene on chromosome 2q33

ICOS Gene Polymorphisms (IVS1 + 173 T/C and c. 1624 C/T) in Primary Sjögren's Syndrome Patients: Analysis of ICOS Expression

Background: Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease, which affects exocrine glands. T cell activation is a trigger mechanism in the immune response. Hyperreactivity of T cells and antibody production are features in pSS. ICOS can be critical in the pathogenesis of pSS. Methods: A total of 134 pSS patients and 134 control subjects (CS) were included. Genotyping was performed by PCR-RFLP. ICOS mRNA expression was quantified by real-time PCR, and CD4+ ICOS+ T cells were determined by flow cytometry. Results: The ICOS IVS1 + 173 T>C polymorphisms were not associated with susceptibility to pSS (p = 0.393, CI = 0.503−1.311). However, the c.1624 C>T polymorphism was associated with a reduction in the risk of development of pSS (p = 0.015, CI = 0.294−0.884). An increase in ICOS mRNA expression in patients was observed (3.7-fold). Furthermore, pSS patients showed an increase in membranal-ICOS expression (mICOS). High expression of mICOS (MFI) was associated with lymphocytic infiltration. Conclusions: The IVS1 + 173 polymorphism is not a genetic marker for the development of pSS, while c.1624 T allele was associated with a low risk. However, elevated mICOS expression in pSS patients with high lymphocytic infiltration was found. ICOS may have an important role in the immunopathogenesis of pSS and should be analyzed in T cell subsets in pSS patients as a possible disease marker.

CTLA-4 Expression Plays a Role in PSC and PBC Progression

BACKGROUND & AIMS

The pathogenesis of primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) remains unclear. The aim of this study was to reveal certain single nucleotide polymorphisms (SNP) in genes for regulatory proteins in the immunologic pathway possibly going along with susceptibility of attaining PBC or PSC.

METHODS

126 patients with either PBC or PSC with clinical and laboratory data were enrolled in the study. SNPs in three genes (CTLA-4, ICOS, and FOX-P3) which are suspected to play a key role in the autoimmune pathway were analyzed to determine allele variants. Gene expression was measured by RealTime PCR using mRNA.

RESULTS

Patients with cirrhosis had a lower number of CTLA-4 copies than patients without cirrhosis (p = 0.04). Accordingly, patients with lower CTLA-4 copies had a poorer recovery of gamma-glutamyltransferase (GGT) in course of their disease (-69.8 U/l vs. -176.1 U/l p = 0.04). Two SNP allele variants (CTLA4 rs733618 and FOXP3 rs2280883) associated with low CTLA-4 expression could be determined. Patients having both variants showed worsening of GGT (-61.7 U/l vs. -132.6 U/l, p = 0.04) and a trend towards a more progressive disease in terms of cirrhosis. (24% vs. 13% p = ns).

CONCLUSIONS

Low expression of CTLA-4 is associated with a more advanced disease in patients with PBC and PSC. Furthermore, we identified two SNP allele variants (CTLA4-SNP rs733618 and FOXP3-SNP rs2280883) associated with a lower CTLA-4 expression and possibly a more severe course of the diseases. Taken together, these results provide further evidence for the involvement of the immune system in the pathogenesis of these two cholestatic liver diseases. Lay summary: Primary biliary cholangitis and primary sclerosing cholangitis are chronic diseases of the bile ducts. Their cause remains widely unclear, but evidence suggests the immune system plays a central role. This study shows that gene alterations connected to the immune system might play a role in the course of the disease.

The Effect of ICOS Polymorphism Interactions with HBV Mutations on HBV Subtype Infection Outcomes

INTRODUCTION AND AIM

Hepatitis B virus (HBV) infection remains a public health problem worldwide. In addition, HBV infection results are influenced by various virological, immunological, and genetic factors. Inducible T-cell costimulator (ICOS) polymorphisms involving chronic HBV infection have been confirmed in previous studies. This study was to explore the effects of ICOS single nucleotide polymorphisms in HBV subtypes and their interactions with viral mutations on HBV infection outcomes.

MATERIAL AND METHODS

A total of 1,636 Han Chinese individuals were recruited, including 47 asymptomatic HBV carriers (ASC), 353 chronic hepatitis B (CHB) patients, 327 HBV-related liver cirrhosis (LC) patients, 193 HBV-related hepatocellular carcinoma (HCC) patients, 464 patients with spontaneous recovery from HBV infection (SR), and 252 healthy controls (HC). DNA samples from these subjects were genotyped for four ICOS SNPs (rs11883722, rs10932029, rs1559931, and rs4675379). Direct sequencing was used to determine the HBV mutations in the enhancer II, basal core promoter, and pre-core regions.

RESULTS

We found that the genotype "TC" of ICOS rs10932029 SNP was associated with decreased HBV-related LC risk in the genotype C group. Additionally, the A1762T, G1764A and A1762T/G1764A mutations were associated with an increased risk of LC in the genotype C group. Further study indicated that interactions between ICOS rs10932029 genotype "TC" and A1762T or A1762T/G1764A mutations significantly decreased the LC risk in the genotype C group.

CONCLUSION

The rs10932029 genotype "TC" might be an LC-protective factor for HBV genotype C infection. The interactions between the rs10932029 genotype "TC" and A1762T or A1762T/G1764A mutations could decrease the risk of LC.

Associations of ICOS and PD.1 Gene Variants with Colon Cancer Risk in The Iranian Population

Background:

Positive and negative co-stimulatory molecules are important factors determining the outcome of immune responses to the presence of tumors. Since co-stimulatory molecule expression may be affected by gene polymorphisms, we aimed to investigate associations between variants of PD.1 and ICOS and susceptibility to colon cancer.

Material and methods:

ICOS (-693A/G), ICOS (+1720C/T) and PD.1 (-538G/A) gene polymorphisms were evaluated by the PCR-RFLP method in 76 colon cancer patients and 73 healthy controls.

Results:

The frequencies of the GG genotype and the G allele at position -693 of the ICOS gene were significantly higher in the patient group (P=0.014 and p=0.0002), while the AA genotype was significantly more common in controls (P=0.0016). At position -538 of PD.1, GG genotype and G allele frequencies were higher in the patient group (P<0.0001and P<0.0001). Again, AA and also AG genotypes significantly predominated in controls (P<0.0001 and P=0.012). Regarding genotypes and alleles of ICOS at position +1720. Frequencies of GCG and GTG haplotypes were higher in patients compared to those of controls (P=0.016 and P<0.0001), while, frequencies of GTA, ATA and ATG haplotypes were higher in controls (P=0.0017, P<0.0001 and P=0.015). GTG/GTG and GTG/GCG double haplotypes were more frequent in patients compared to controls (P=0.0147 and P=0.0071).

Conclusion:

Our study clarified that PD.1 (-538G/A) and ICOS (-693A/G) gene polymorphisms can be considered as genetic risk factors for the development of colon cancer among Iranian patients.

Understanding Celiac Disease From Genetics to the Future Diagnostic Strategies

Celiac disease (CD) is an autoimmune disorder characterized by the permanent inflammation of the small bowel, triggered by the ingestion of gluten. It is associated with a number of symptoms, the most common being gastrointestinal. The prevalence of this illness worldwide is 1%. One of the main problems of CD is its difficulty to be diagnosed due to the various presentations of the disease. Besides, in many cases, CD is asymptomatic. Celiac disease is a multifactorial disease, HLA-DQ2 and HLA-DQ8 haplotypes are predisposition factors. Nowadays, molecular markers are being studied as diagnostic tools. In this review, we explore CD from its basic concept, manifestations, types, current and future methods of diagnosis, and associated disorders. Before addressing the therapeutic approaches, we also provide a brief overview of CD genetics and treatment.

The Association Between Viral Infections and Co-stimulatory Gene Polymorphisms in Kidney Transplant Outcomes

Background

The surveillance of kidney transplant patients depends on function of different immunologic markers like co-stimulatory molecules. These molecules may also be associated with post kidney transplant viral related outcomes.

Objectives

The aim of this study was to investigate the possible associations between co-stimulatory molecule gene polymorphisms and viral infections in kidney transplant patients.

Patients and Methods

In total, 172 kidney transplant patients were included in this study. Single nucleotide polymorphisms in loci of co-stimulatory molecules including: PDCD.1, CD28, CTLA4 and ICOS, were analyzed in the studied patients by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. Active Cytomegalovirus (CMV) infection and history of hepatitis C virus (HCV) infection were analyzed in each kidney transplant patient using the CMV antigenemia kit and HCV antibody assay, according to the manufacturer’s instructions.

Results

CMV active infection was found in 31 of 172 (18.02%) kidney transplant patients. HCV infection was only found in two of the 172 (1.16%) studied patients. Significant associations were found between TT and TC genotypes of CTLA4 -1722T/C and T allele with acute rejection in CMV infected kidney transplant patients. A significant association was also found between the T allele of CD28 + 17 C/T genetic polymorphism and acute rejection in CMV infected kidney transplant patients. Significantly higher frequency of AA genotype and A allele of CTLA4 + 49AG polymorphism were found in CMV infected female patients. Also a significantly higher frequency of GG genotype and G allele of PDCD-1.3A/G polymorphisms were found in CMV infected female patients.

Conclusions

Based on these results, CTLA4 and CD28 genetic polymorphisms, which regulate T-cell activation, can influence active CMV infection in kidney transplant patients. These results should be confirmed by further investigations.

Association of Inducible T Cell Costimulator Polymorphisms with Susceptibility and Outcome of Hepatitis B Virus Infection in a Chinese Han Population

Inducible T cell costimulator (ICOS) functions to regulate cell-cell signalling, immune responses and cell proliferation. ICOS single nucleotide polymorphism (SNP) may affect protein expression and functions. This study investigated the association of ICOS SNPs with hepatitis B virus (HBV) infection and outcome in a Chinese population. A total of 1290 Chinese Han individuals were enrolled, including 63 asymptomatic HBV carriers, 220 chronic hepatitis B patients (CHB), 249 HBV-related liver cirrhosis patients (LC), 108 patients with HBV-related hepatocellular carcinoma (HCC), 338 patients with natural HBV clearance and 312 healthy subjects (as controls). DNA samples from these subjects were genotyped for four ICOS SNPs (rs11883722, rs10932029, rs1559931 and rs4675379) using TaqMan SNP Genotyping Assay and analysed. The data showed that genotype and allele frequencies of ICOS SNPs in cases and controls followed the Hardy-Weinberg distribution. The CC genotype of rs4675379 was higher in patients with HBV infection (including AC, CHB, LC and HCC) than in patients with HBV clearance (P = 0.006). Furthermore, the genotype 'GA' and the minor allele 'A' of rs1559931 were associated with a decreased HCC susceptibility (P < 0.001). Haplotype analysis data showed that 'GC' haplotype in block 2 (rs1559931 and rs4675379) had a lower frequency in patients than in HBV-cleared subjects (P = 0.034), although its overall frequency was only 1.6%. Our study found that ICOS rs1559931 SNP was associated with decreased HBV-related HCC risk in the studied Chinese Han population, except for patients with natural clearance of HBV.

Molecular mechanisms of the adaptive, innate and regulatory immune responses in the intestinal mucosa of celiac disease patients

Celiac disease is a complex genetic disorder that affects the small intestine of genetically predisposed individuals when they ingest gluten, a dietary protein. Although several genome screens have been successful in identifying susceptibility loci in celiac disease, the only genetic contributors identified so far are the human leukocyte antigen (HLA)-DQ2/DQ8 molecules. One of the most important aspects in the pathogenesis of celiac disease is the activation of a T-helper 1 immune response, when the antigen-presenting cells that express HLA-DQ2/DQ8 molecules present the toxic gluten peptides to reactive CD4(+) T-cells. Recently, new insights into the activation of an innate immune response have also been described. It is generally accepted that the immune response triggers destruction of the mucosa in the small intestine of celiac disease patients. Hence, the activation of a detrimental immune response in the intestine of celiac disease patients appears to be key in the initiation and progression of the disease. This review summarizes the immunologic pathways that have been studied in celiac disease thus far, and will point to new potential candidate genes and pathways involved in the etiopathogenesis of celiac disease, which should lead to novel alternatives for diagnosis and treatment.

The effect of gluten-free diet on Th1-Th2-Th3-associated intestinal immune responses in celiac disease

OBJECTIVE

To study T-helper (Th)1-Th2-Th3 gene activation profile in the small intestine and peripheral blood of children with celiac disease (CD) with special interest in the response to the gluten-free diet (GFD) treatment in order to elucidate an immune dysregulation not triggered by gluten.

MATERIAL AND METHODS

Small intestinal biopsies and venous blood were taken from seven children with CD (mean age: 8 years, four girls) at presentation and after 1 year of strict GFD. The Th1-Th2-Th3 gene expression profile was examined by real-time PCR arrays. The findings were compared with the corresponding expressions in peripheral blood and small intestinal biopsies from six reference children without CD (mean age: 6 years, four girls).

RESULTS

The Th1 gene expression profile including interferon (IFN)-γ, signal transducer and activator of transcription (STAT) 1 and interferon regulatory factor (IRF) 1 together with reduced interleukin (IL)-2 expression was pronounced in small intestinal biopsies from children with untreated CD. A downregulation of IFN-γ transcripts was seen after 1 year of GFD, but there was still increased expression of STAT1 and IRF1 in association with low IL-2 expression in spite of eliminated exposure to wheat gluten. By contrast, the decreased intestinal expression of Th2 gene markers observed at presentation was normalized with GFD. The alterations in the mucosal gene expression profile were not reflected in peripheral blood.

CONCLUSION

The GFD did not correct the increased activation of the IFN-γ signaling pathway related markers and reduced IL-2 expression, suggesting that they represent an immune dysregulation not dependent on gluten exposure.

Association of T-cell regulatory gene polymorphisms with oral squamous cell carcinoma

Costimulatory molecules have complementary effects on T-cell activation and their balance may control the development of oral cancer. The aim of this study was to determine the relevance of cytotoxic T-lymphocyte antigen 4 (CTLA-4), CD28 and inducible costimulator (ICOS) polymorphisms in oral squamous cell carcinoma (OSCC). Genotyping for CTLA-4 (-1661 A/G and +49 A/G), CD28 (0 C/G and +3160 G/T) and ICOS (+637 A/C and +1599 C/T) was performed in the 83 patients with OSCC, compared to the 40 unrelated healthy volunteers as controls. The genotype CTLA-4 -1661 was significantly different between the patient group and the control group. The allele CTLA-4 -1661 G was significantly found more frequent in patients with OSCC (p=0.001). In bivariate analysis, noticeable differences between OSCC and controls were seen. The combinations CTLA-4 -1661 G/G and CTLA-4 +49 A/G, ICOS +1559 C/T and ICOS +1559 C/C each with CTLA-4 -1661 G/G, ICOS +637 C/C and ICOS +637 A/C each with CTLA-4 -1661, CTLA-4 -1661 A/G and ICOS +637 C/C, CD28 +3160 G/T and CTLA-4 -1661 A/A and CD28 +3160 G/T and CTLA-4 -1661 A/G were seen in the patient group only. Especially the polymorphisms of the CTLA-4 -1661-genotype - alone and in combination with other T cell regulator polymorphisms - seem to be possible predisposing factors for OSCC. Therefore, they might be future targets for a primary prophylaxis or an individualised therapy.

ICOS Gene Polymorphism May Be Associated with Pemphigus

Background:

Pemphigus is an autoimmune blistering disease mediated by circulating IgG autoantibodies directed against desmogleins 3 and/or 1. As pemphigus is a T cell–mediated disease, one may assume that genetically determined disregulation of costimulatory signal may be involved in its pathogenesis.

Objective:

The aim of the present study was to evaluate the relationship between polymorphisms in genes encoding costimulatory receptors, CTLA4 and ICOS, and pemphigus in the Polish population.

Methods:

The study included 54 patients with pemphigus: 40 with pemphigus vulgaris (PV) and 14 with pemphigus foliaceus (PF). Additionally, 176 healthy unrelated blood donors served as controls. +49A/G CTLA4 and IVS1+173 ICOS polymorphisms were identified using a modified polymerase chain reaction–restriction fragment-length polymorphism.

Results:

Analysis of the frequency of genotypes and alleles of +49A/G CTLA4 gene polymorphism showed no statistically significant differences between the PV and PF patients and the controls. The distribution of genotypes in IVS1+173 ICOS polymorphisms was significantly different in both PV ( p < .01) and PF ( p = .0004) patients when compared to controls. The carriers of the allele C were more frequent in PV or PF in comparison with the control group ( p < .001 for both groups).

Conclusions:

Our results suggest that genetically determined abnormal function of costimulatory receptors in T cells may be associated with the pathogenesis of pemphigus.

Long-term and acute effects of gliadin on small intestine of patients on potentially pathogenic networks in celiac disease

Celiac disease (CD) is a complex, immune-mediated intolerance to gliadin that develops in genetically susceptible individuals. Although the main driving force of the disease is an aberrant autoimmune response, several other pathogenic mechanisms, many still unidentified, are also involved. In order to describe at a network level the alterations provoked by a gliadin insult on the intestinal mucosa of patients, we compared the expression profiles of biopsies from 9 active and 9 treated patients (long-term effects of gliadin), and of 10 biopsies from gluten-free diet treated patients that were incubated in vitro with or without gliadin (acute effects) and integrated significantly altered transcripts into potentially pathogenic biological processes. Using information on Kyoto Encyclopedia of Genes and Genomes pathways and Gene Ontology terms represented among the differentially expressed genes, we observed important dysfunction in several complex networks, including those related to cell-cell communication, intracellular signaling, ubiquitin-proteasome system, cell cycle/apoptosis and extracellular matrix. The reconstruction of the role of these biological networks in the development of the intestinal lesion in CD provides a comprehensive picture of key events that contribute to the disease, and could point towards novel functional candidates that might be potential therapeutic targets or responsible for genetic susceptibility.

Fine mapping of the CELIAC2 locus on chromosome 5q31-q33 in the Finnish and Hungarian populations

Celiac disease is a chronic inflammation of the small intestine, arising in genetically predisposed individuals as a result of ingestion of dietary gluten. The only confirmed and functionally characterised genetic risk factors for celiac disease are the DQ2 or DQ8 heterodimers at the major histocompatibility complex (MHC) class II locus (CELIAC1). These genes are necessary but alone not sufficient for disease onset. Genome-wide linkage scans have suggested chromosome 5q31-q33 (CELIAC2) as an important risk locus for celiac disease. This region has also been associated to other inflammatory disorders, although as yet, no clear gene associations have been found. In the current study, 11 celiac disease candidate loci were screened for genetic linkage in the Hungarian population. As the CELIAC2 locus showed the strongest evidence for linkage, this locus was selected for follow-up. Seventeen candidate genes were selected from the CELIAC2 locus, and genotyped using 48 haplotype tagging single nucleotide polymorphisms (SNPs) in large Finnish and Hungarian family materials. A subset of these, 40 tagging SNPs in 15 genes, were genotyped in an independent set of Finnish and Hungarian cases and controls. We confirmed linkage of this region with celiac disease and report strong linkage in both the Finnish and Hungarian populations. The association analysis showed modest associations throughout the whole region. These association findings were not replicated in the case-control datasets. Our study strongly supports the role of the CELIAC2 locus in celiac disease, but it also highlights the need for a more powerful study design in the region, to locate the true disease risk variants.

Association between genotypes and phenotypes in coeliac disease

BACKGROUND

Coeliac disease (CD) is a genetically driven immunological intolerance to dietary gluten with a wide range of clinical presentations. The aim of this study was to investigate the heritability of the phenotype in CD and the influence on the phenotype of different genes associated with the disease.

PATIENTS AND METHODS

One hundred and seven families with at least 2 siblings with CD were collected. The patients were grouped in symptom grades on the basis of the clinical presentation, the age at diagnosis, and sex. Stratification analyses of the human leucocyte antigen-DQA1 and human leucocyte antigen-DQB1 genotypes, the CTLA4 +49A/G polymorphism, the CTLA4 haplotype MH30*G:-1147*T:+49*A:CT60*G:CT61*A, and the 5q31-33 loci were done.

RESULTS

The heritability of the phenotype was estimated to be 0.45. Significant association and linkage was found between the clinical presentation and the CTLA4 +49A/G polymorphism but not for the other genotypes. No correlation was found between genotypes and age at diagnosis or sex.

CONCLUSIONS

Our results indicate that the heritability is determiner of the phenotype in CD. The CTLA4 +49A/G polymorphism is correlated to the clinical presentation: the AA genotype is associated with clinically silent disease.

The role of costimulation in antibody deficiencies: ICOS and common variable immunodeficiency

SUMMARY

The identification of mutations in the inducible costimulator (ICOS) gene in nine patients with common variable immunodeficiency (CVID) was a major breakthrough. CVID is a complex, highly heterogeneous primary immunodeficiency disease, and the discovery of these mutations revealed a molecular basis. ICOS belongs to the CD28 family of costimulatory molecules and is expressed exclusively on activated T cells. It has at least three critical functions: germinal center formation, isotype class switching, and the development of memory B cells. The discovery of human ICOS deficiency showed that a monogenic disorder could account for the full spectrum of manifestations seen in childhood and adulthood-onset CVID, including autoimmune, inflammatory, and malignant disease complications, as well as recurrent infections. Moreover, this discovery showed that a disorder which had previously been perceived as a B-cell disease might in fact have its genetic origin in human T cells. In this article, we review the role of ICOS in the mammalian immune system and human disease, as well as the discovery and characteristics of patients with ICOS deficiency. Finally, we also discuss how these 'human knockouts' have contributed to our understanding of ICOS functions and have suggested potential avenues for using therapeutic ICOS manipulation to treat other diseases.

A common CTLA4 polymorphism confers susceptibility to autoimmune thyroid disease in celiac children

BACKGROUND

Cytotoxic T-lymphocyte-associated protein 4 (CTLA4) is a strong candidate gene in autoimmunity susceptibility. In particular, the CTLA4 CT60 A/G dimorphism has been associated with celiac disease (CD) and was reported to be strongly associated with autoimmune thyroid disease (AITD).

AIMS

This study aimed to investigate the possible influences of the CTLA4 CT60 A/G polymorphism in the susceptibility of Italian children to CD and in the predisposition to develop AITD in children with CD.

PATIENTS AND METHODS

We genotyped 317 Italian celiac children, including 44 patients (13.9%) who developed AITD after CD diagnosis and 350 controls.

RESULTS

The CTLA4 CT60 GG genotype distribution did not show any significant difference between children with CD and control population (p=0.4). On the contrary, the frequency of the GG genotype was significantly higher in patients with CD complicated with AITD than in control subjects (p=0.002) and CD patients without AITD (p=0.02).

CONCLUSION

Our data show a significant effect of the CTLA4 CT60G allele at the homozygous state on the risk of developing AITD in children with CD and suggest that the reported association of the CTLA4 CT60 A/G polymorphism with CD is limited to the subgroup of patients who are or will be complicated with AITD.

Functional polymorphism of CTLA-4 and ICOS genes in allogeneic hematopoietic stem cell transplantation

BACKGROUND

T cells play a critical role in alloimmune recognition and thus contribute to graft-versus-host disease (GVHD) and relapse prevention in hematopoietic stem cell transplantation (HSCT). Cytotoxic T lymphocyte antigen-4 (CTLA-4) and inducible costimulator (ICOS) are costimulatory molecules of T cell activation and their genetic variations can affect the capacity of T cells to become activated or inactivated.

METHODS

We examined CTLA-4 (-318 C/T and +49 A/G) and ICOS (c.602 A/C and c.1624 C/T) genotypes in 123 patients with HSCT and their HLA-matched sibling donors, and then evaluated the impacts of the genetic polymorphisms on GVHD, disease relapse, and survival.

RESULTS

By multivariate analysis, the donor CTLA-4 -318 TT genotype increased the risk of disease relapse (Hazard ratio [HR]: 5.91, 95% confidence interval [CI]: 1.17-29.79, P=0.0313). Recipients who received a graft from a donor with ICOS c.602 CC genotype had worse disease-free survival (HR: 5.97, 95% CI: 1.49-23.87, P=0.0115). Additionally, recipients with ICOS c.1624 TT genotype had worse overall survival (HR: 12.98, 95% CI: 2.58-65.35, P=0.0019). Nevertheless, CTLA-4 and ICOS genotypes were not associated with acute and chronic GVHD.

CONCLUSIONS

Both donor and recipient CTLA-4 and ICOS gene polymorphisms might be of importance for the outcome of allogeneic HSCT.

Association of genetic variation in inducible costimulator gene with outcome of kidney transplantation

BACKGROUND

The closely-linked genes of CD28, cytotoxic T-lymphocyte associated antigen 4 (CTLA4), inducible costimulator (ICOS), and programmed cell death 1 on chromosome 2q encode costimulatory molecules, which are regulators of the T-cell activity. The T-cell mediated immune response has a major role in allograft rejection. Hence, the variation in these genes may have an effect on graft survival and the amount of immunosuppression needed, but so far the studies have restricted solely to the CTLA4 gene.

METHODS

We determined 13 single nucleotide polymorphisms in CD28, CTLA4, ICOS, and PPCD1 genes in 678 adult patients who received a kidney from deceased donor. The effect of genetic variation on the outcome of renal transplantation was analyzed.

RESULTS

Two markers on the ICOS gene, rs10183087 and rs4404254, were associated with delayed graft function (odds ratio=5.8; P=0.020 and odds ratio=5.8; P=0.019, respectively). Interestingly, the same ICOS variation has been shown to regulate the expression level of ICOS. We also demonstrated an association of the ICOS polymorphism rs10932037 with the graft survival (P=0.026).

CONCLUSIONS

The present results indicate that potentially functional genetic variation in T-cell costimulatory molecule ICOS has an effect on the outcome of kidney transplantation.

Genetic analysis of the exon 1 position 49 CD152 dimorphism in multiple sclerosis

Several studies have examined whether a dimorphism in the CD152 costimulatory molecule may influence the development of multiple sclerosis (MS). A sample of 108 patients with a diagnosis of relapsing remitting (RRMS), 28 with secondary progressive (SPMS), 23 with primary progressive (PPMS) and 63 people with no prior history of neurological conditions were selected from the MS clinic at the University of Texas Southwestern Medical Center at Dallas. Peripheral blood was separated with gradient extraction for leukocytes and genomic DNA extracted for CD152 A/G dimorphism analysis. A 163 bp PCR product in exon 1 including the position 49 A/G dimorphism was examined via single strand conformation polymophism (SSCP). Patient haplotype frequencies were compared between cases and controls and Pearson Chi-Square test performed to demonstrate statistical differences between MS groups and controls. Our results, similar to several recent studies, suggest that there is no statistical association with the risk of developing MS and no increased frequency in A or G at position 49 of exon 1 of CD152. Demonstration of prolonged proliferation in patient samples containing the GG genotypes and altered CD152 surface expression was also not demonstrated suggesting that the CD152 exon 1 position 49 A/G dimorphism does not contribute significantly to the development of MS in this patient population.

Toll-like receptor 4 (TLR4) gene polymorphisms in celiac disease

Toll-like receptors (TLRs) participate in the first line of immune defense through antigen pattern recognition, and ligands include exogenous and host-derived molecules. Coding variants in TLR4 have been associated with autoimmune diseases like ulcerative colitis, Crohn's disease, and rheumatoid arthritis. Our aim was to determine whether these polymorphisms are associated with celiac disease (CD). Two coding single nucleotide polymorphisms of TLR4 (Asp299Gly and Thr399Ile) were genotyped in 95 family trios with CD as well as in 186 patients and 186 unrelated controls. There were no differences in allele, genotype or haplotype distribution, or transmission between patient and control groups. Our results do not support association of these TLR4 variants with CD.

Genetic analyses of celiac disease in a Spanish population confirm association with CELIAC3 but not with CELIAC4

Genetic predisposition to celiac disease (CD) is determined primarily by the human leukocyte antigen (HLA) genes (CELIAC1 region; 6p21), although many loci are involved in disease susceptibility. First, we have analysed a large series of CD patients from the Spanish Mediterranean region who had previously been characterised for the HLA complex. We have investigated how relevant regions contribute to CD susceptibility: CELIAC3 (CD28/CTLA4/ICOS region on 2q33) and CELIAC4 (19p13) as well as the tumour necrosis factor alpha (TNF-alpha) and the linfotoxin loci by case-control and association analyses. We highlight the association with the +49*A allele of cytotoxic T-lymphocyte-associated antigen 4 locus (P = 0.01), and the -308*A of TNF-alpha locus (P = 0.0008) in DQ2 individuals, although an independent role for TNF-alpha as risk factor has not been proven. Moreover, we do not confirm the association with the CELIAC4 region polymorphisms described in other populations.

Searching for genes influencing a complex disease: the case of coeliac disease

Recently, a few genes have been reported to be causative in inflammatory diseases. Still, we are waiting for the vast majority to be discovered. New tools for genotyping and statistical analysis have been developed and emphasis has been put on study design. Coeliac disease (CD) is a disorder, where prolamins in dietary wheat gluten and related proteins from rye or barley are not tolerated. It is one of the most common chronic diseases in humans exceeding a population prevalence of 1%. In this article, we will summarise what is currently known about the genetics influencing CD with the emphasis on the non-HLA genetic component. We will discuss some difficulties when searching for susceptibility genes in disorders with complex inheritance patterns.

ICOS gene haplotypes correlate with IL10 secretion and multiple sclerosis evolution

Human ICOS is a T cell costimulatory molecule supporting IL10 secretion. A pilot study investigating variations of the ICOS gene 3'UTR detected 8 polymorphisms forming three haplotypes (A, B, C). Haplotype-A and -C displayed the highest difference. Activated T cells from healthy AA homozygotes expressed significantly less ICOS and secreted more IL10 than AC heterozygotes, whereas AB heterozygotes displayed intermediate levels. Analysis of 441 multiple sclerosis patients and 793 controls showed that frequency of AA homozygosity was significantly lower in MS patients with relapsing-remitting onset (N=416) than in controls (OR=0.70). Moreover, AA patients with relapsing-remitting onset had lower relapse rate and multiple sclerosis severity score than non-AA patients.

Association of KIR2DL5B gene with celiac disease supports the susceptibility locus on 19q13.4

Genome-wide scans have detected linkage to celiac disease (CD) in several genomic locations, including 19q13.4. Killer immunoglobulin-like receptor (KIR) genes map to the region and encode receptors of natural killer (NK) cells and certain T cells that modulate cytolitic activity through interactions with HLA class I ligands, participating in the innate immune response. We performed KIR genotyping in a group of 70 CD patients of Basque origin and compared gene content, genotype and haplotype frequencies to ethnically matched blood-donors. The frequency of gene combination KIR2DL5B(+)/KIR2DL5A(-) was significantly higher in the disease group, and this result was confirmed in a second group of 343 CD patients and 160 controls of Spanish origin, suggesting an implication of this 'unexpressed' gene with increased susceptibility to CD (combined OR of 3.63 (95% CI: 1.76-7.51; P=0.0004)), possibly due to the lack of an efficient inhibitory signal. Our results support the role of the KIR gene cluster in celiac disease and replicate the CD-susceptibility locus at 19q13.4.

Signatures of strong population differentiation shape extended haplotypes across the human CD28, CTLA4, and ICOS costimulatory genes

The three members of the costimulatory receptor family, CD28, CTLA-4, and ICOS, have complementary effects on T cell activation, and their balance controls the overall outcome of immune and autoimmune responses. They are encoded in a short genomic interval, and overall activity may result from interplay between allelic variants at each locus. With multiethnic DNA panels that represent a wide spectrum of human populations, we demonstrate long-range linkage disequilibrium among the three genes. A large fraction of the variation found in the locus can be explained by the presence of extended haplotypes encompassing variants at CD28, CTLA4, and the ICOS promoter. There are unusual differences in the distribution of some variants and haplotypes between geographic regions. The differences may reflect demographic events and/or the adaptation to diverse environmental and microbial challenges encountered in the course of human migrations and will be important to consider when interpreting association to immune/autoimmune responsiveness.

Genetic variation in ICOS regulates mRNA levels of ICOS and splicing isoforms of CTLA4

Genetic and functional studies suggest that polymorphism in cytotoxic T lymphocyte-associated antigen-4 (CTLA4) and inducible costimulator (ICOS) genes, both reported to harbour autoimmune susceptibility loci, could regulate the immune activation through affecting their expression and splicing of CTLA4. To address this, we studied expression of CTLA4 and ICOS and the role of polymorphisms in the gene region by measuring the relative amounts of transcripts, including the soluble CTLA4 (sCTLA4) splicing isoform in healthy volunteers. We combined a physiologically relevant in vitro activation for human CD4(+) T lymphocytes and a quantitative RT-PCR. The susceptibility allele CT60G in CTLA4 gene was confirmed to be associated with a decreased amount of sCTLA4, but only in resting cells. During the T cell activation two genetic variants in ICOS gene, IVS1+173T/C and c.1624C/T, affected expression of CTLA4 isoforms and ICOS, respectively. We could not confirm that the level of sCTLA4 is down-regulated following T lymphocyte activation, instead the levels of CTLA4 splicing isoforms correlated to each others. Our results indicate that genetic variation in this gene region regulates the expression of both CTLA4 and ICOS and not only the splicing of sCTLA4 as suggested earlier.

Celiac disease and HLA in a Bedouin kindred

We report the prevalence of celiac disease (CD) and its relationship with other autoimmune diseases and HLA haplotypes in a Bedouin kindred. Of 175 individuals sampled and typed for autoantibodies and HLA class II genotypes, six (3.4%) members had CD, and an additional 10 (5.7%) members tested positive for autoantibodies to transglutaminase (TgAA+). Several CD/TgAA+ relatives also had islet cell antigen or adrenal autoimmunity. Affected relatives are more closely related than expected from the pedigree relationships of all family members and were more often the offspring of consanguineous marriages. Individuals with CD or TgAA+ were enriched for DRB1*0301-DQA1*0501-DQB1*0201, a haplotype previously reported as high risk for CD. There was also an increased frequency of DQB1*0201/DQB1*0201 homozygotes among affected relatives. We found no evidence that DRB1*0701-DQA1*0201-DQB1*0201/DRB1*11-DQA1*0501-DQB1*0301 is a high-risk genotype, consistent with other studies of Arab communities. In addition, a nonparametric linkage analysis of 376 autosomal markers revealed suggestive evidence for linkage on chromosome 12p13 at marker D12S364 (NPL = 2.009, p = 0.0098). There were no other significant results, including the HLA region or any other previously reported regions. This could reflect the reduced power of family-based linkage and association analyses in isolated inbred populations.

Association of T-cell regulatory gene polymorphisms with susceptibility to gastric mucosa-associated lymphoid tissue lymphoma

PURPOSE

Helicobacter pylori infection and host susceptibility interact to develop gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and activation of specific T cells might play a crucial role in this process. Recent investigations show that the CTLA4, CD28, and ICOS genes are located on chromosome 2q33 and their polymorphisms confer susceptibility to infectious and immune diseases through deregulation of T-cell stimulation. We aimed to determine the role of CTLA4, CD28, and ICOS polymorphisms in gastric MALT lymphoma.

PATIENTS AND METHODS

Genotyping for CTLA4 (49 A/G, -318 C/T, and CT60 A/G), CD28 (IVS3+ 17T/C), and ICOS (c.602 A/C and c.1624C/T) was performed for 62 patients with gastric MALT lymphoma and compared with 250 unrelated healthy controls.

RESULTS

H pylori infection was significantly higher in patients with gastric MALT lymphoma (90.3%) compared with controls (66.4%; P < .001). The CTLA4 -318 C/T genotype was associated with a lower risk of developing gastric MALT lymphoma (odds ratio [OR] = 0.3; P = .022), whereas CTLA4 49 G/G genotype was linked to a higher risk (OR = 4.1; P = .044). In patients with H pylori infection, CTLA4 49 G/G genotype was associated with an even higher risk (OR = 6.4; P = .047). Carriage of the tightly linked -318C -49G haplotype conferred a four-fold higher susceptibility to MALT lymphoma (OR = 4.2; P = .042). Complete remission after H pylori eradication was related to tumor stage but not to genotypes or haplotypes.

CONCLUSION

These results indicate a genetic link of CTLA4 gene polymorphisms to development of gastric MALT lymphoma and indirectly support the crucial role of host activated T cells in the MALT lymphomagenesis.

Regulation of T:B cell interactions by the inducible costimulator molecule: does ICOS "induce" disease?

The Inducible Costimulator molecule (ICOS), a member of the CD28 family of costimulatory molecules, was identified in 1999 as a molecule expressed primarily on activated human T cells. Induced upon activation, ICOS appears to be an ideal target for modifying T-cell-mediated immune responses. ICOS was also found to be highly expressed on germinal center T cells, suggesting that ICOS was involved in T:B cell interactions. While ICOS has subsequently been shown to be important for both Th1 and Th2 cell activation and effector function, a central role for ICOS in the generation and maintenance of humoral immunity is emerging. In this review, we summarize the evidence that the level of ICOS expression regulates T-cell-dependent B cell responses and propose a model for the role of ICOS in diseases characterized by dysregulated humoral immunity.

The downstream modulator of interferon-γ, STAT1 is not genetically associated to the Dutch coeliac disease population

Coeliac disease (CD) is a complex genetic disorder. Its etiology is owing to multiple genes and environmental factors, such as gluten. The first event in the pathogenesis of CD after the ingestion of gluten is the activation of a Th1 immune response that leads to villous atrophy. Although this immune response seems crucial to the disease's development, only the HLA-DQ2/DQ8 genes have been identified as causative immune genes related to CD. Recently, the activation of the transcription factor STAT1 and changes in its expression levels have confirmed the participation of the Janus kinase-signal transducer and activator of transcription pathway in CD. Furthermore, as the STAT-1 gene is a positional candidate located in the CELIAC3 locus on chromosome 2, we speculate that alterations in this gene could be primarily responsible for the aberrant immune response that characterizes CD. Based on this functional and genetic evidence, we investigated the primary contribution of STAT-1 to CD. We performed a comprehensive genetic association study using five tag SNPs fully covering the STAT-1 gene in a Dutch cohort of 355 independent CD cases and 360 healthy controls. Neither the alleles, nor the genotypes in the case-control genetic association studies, nor the haplotype analysis showed any association to the STAT-1 gene in the Dutch CD population. Our results do not point to a primary involvement of the STAT-1 gene in the Dutch CD population.

Functional polymorphism of the NFKB1 gene promoter is not relevant in predisposition to celiac disease

OBJECTIVE

The nuclear factor (NF)-kappaB is one of the pivotal regulators of autoimmunity and inflammation, which has been shown to be activated in the inflamed mucosa of patients with celiac disease (CD). Recently, in the NFKB1 gene promoter region, a common insertion/deletion (-94ins/delATTG) polymorphism located between two putative key promoter regulatory elements was described. The aim of this study was to investigate the contribution of the -94ins/delATTG NFKB1 gene promoter functional variant to CD genetic predisposition.

MATERIAL AND METHODS

A case-control cohort comprising 478 patients with CD and 711 healthy controls as well as a panel of 196 celiac families was genotyped for the 94ins/delATTG NFKB1 polymorphism, using a polymerase chain reaction (PCR) method combined with fluorescence technology.

RESULTS

We found no statistically significant differences between CD patients and controls when the -94ins/delATTG genotype and allele distributions were compared. Accordingly, the familial analysis did not reach statistically significant deviation in the transmission of -94ins/delATTG alleles to the affected offspring.

CONCLUSIONS

From these results, it could be suggested that the -94ins/delATTG NFKB1 polymorphism does not play a major role in CD susceptibility.

Cutting edge: polymorphisms in the ICOS promoter region are associated with allergic sensitization and Th2 cytokine production

The establishment of ICOS as an important regulator of Th2 development and effector function makes the ICOS locus an attractive candidate for Th2-mediated diseases, such as asthma and allergy. In evaluation of this candidate locus in humans, we identified 11 variants and determined that two in the putative promoter region are significantly associated with allergic sensitization and serum IgE levels. In addition, cultures of activated PBMCs from individuals homozygous for the associated polymorphisms produced increased levels of the Th2 cytokines, IL-4, IL-5, and IL-13, as well as TNF-alpha compared with controls. One of the polymorphisms, -1413G/A, demonstrated differential NF-kappaB binding in mobility shift analysis, suggesting that this polymorphism has functional consequences. Overall, these data demonstrate that ICOS is a susceptibility gene for allergic sensitization, perhaps through the promotion of Th2 differentiation.

Haplotypes in the CTLA4 region are associated with coeliac disease in the Irish population

Chromosomal region 2q33 encodes the immune regulatory genes, CTLA4, ICOS and CD28, which are involved in regulation of T-cell activity and has been studied as a candidate gene locus in autoimmune diseases, including coeliac disease (CD). We have investigated whether an association exists between this region and CD in the Irish population using a comprehensive analysis for genetic variation. Using a haplotype-tagging approach, this gene cluster was investigated for disease association in a case-control study comprising 394 CD patients and 421 ethnically matched healthy controls. Several SNPs, including CTLA4_CT60, showed association with disease; however, after correction for multiple-testing, CTLA4-658C/T was the only polymorphism found to show significant association with disease when allele, genotype, or carrier status frequency were analysed (carrier status (Allele C), P = 0.0016). Haplotype analysis revealed a haplotype incorporating the CD28/CTLA4 and two 5' ICOS polymorphisms to be significantly associated with disease (patients 24.1%; controls 31.5%; P = 0.035), as was a shorter haplotype composed of the CTLA4 markers only (30.9 vs 34.9%; P = 0.042). The extended haplotype incorporating CD28/CTLA4 and 5' ICOS is more strongly associated with disease than haplotypes of individual genes. This suggests a causal variant associated with this haplotype may be associated with disease in this population.

CTLA4/CT60 polymorphism is not relevant in susceptibility to autoimmune inflammatory intestinal disorders

The aim of this work was to investigate the possible influence of the recently described CT60 A/G dimorphism of the CTLA4 (cytotoxic T-lymphocyte antigen 4) gene in the susceptibility to two different autoimmune inflammatory intestinal disorders, inflammatory bowel disease (IBD) and celiac disease. We analyzed a case-control cohort composed of 528 Spanish patients with IBD (284 with Crohn disease and 244 with ulcerative colitis) and 454 unrelated healthy individuals, and additionally a group of 90 celiac disease families. CT60 genotyping was performed with a TaqMan 5' allelic discrimination assay. After comparing patients with IBD with the control population, we found no significant deviation in the distribution of the alleles or genotypes of CTLA4/CT60 dimorphism. In addition, by means of familial and case-control analysis, no evidence for a statistically significant association was observed between CTLA4/CT60 and celiac disease susceptibility. Therefore, our results suggest that the CTLA4/CT60 polymorphism does not play a major role in inflammatory intestinal disorders.

A common CTLA4 haplotype associated with coeliac disease

Coeliac disease is a common enteropathy with a strong inherited risk characterised by dietary wheat, rye and barley induced T-cell activation. Although there is replicated linkage to 2q33, results are inconsistent from association studies of the most promising candidate genes: the CD28/CTLA4/ICOS cluster. CTLA4 plays a key role in regulating T lymphocyte mediated inflammatory responses, and variants in the 3' region influence development of diabetes and thyroid disease. We genotyped CTLA4 variants (-1722 C/T, -658 T/C, -318 C/T, +49 A/G, +1822 C/T, CT60 A/G) to tag all common haplotypes (>5% frequency) and an ICOS variant (IVS+173 C/T) in 340 white UK Caucasian coeliac disease cases. Strict ascertainment criteria for coeliac cases required both villous atrophy at diagnosis and positive serology. In total, 973 healthy controls were available for SNP, and 705 for CTLA4 haplotype, based association analyses. Coeliac disease showed weak association with the CTLA4 +1822T (P=0.019) and CT60 G (P=0.047) alleles. Strong association was seen with a common CTLA4 haplotype (P=0.00067, odds ratio 1.41) of frequency 32.7% in coeliac disease and 25.5% in healthy controls. A common CTLA4 haplotype shows strong association with coeliac disease, and contains multiple alleles reported to affect immunological function. Loss of tolerance to dietary antigens in coeliac disease may be mediated in part by heritable variants in co-signalling genes regulating T-cell responses.

Genetic analysis of the 2q33 region containing CD28-CTLA4-ICOS genes: association with non-Hodgkin's lymphoma

There is strong evidence that altered immunological function entails an increased risk of lymphoma, although the current knowledge of aetiological factors for lymphomas is limited. The CTLA4 gene encodes a receptor that provides a negative signal to the T-cell once an immune response is initiated and completed. We analysed the 2q33 chromosomal region harbouring CD28, CTLA4 and ICOS genes, which are closely linked and have related functions in immune regulation, for association in 100 non-Hodgkin's lymphoma (NHL) patients and in 128 healthy controls; both groups originated from Sardinia. There was a strong association of the CTLA4 49A and the 3'-untranslated region (AT)(82) alleles with NHL [odds ratio (OR) = 2, 95% confidence interval (CI) = 1.2-3.2, and OR = 1.6, 95% CI = 1.1-2.4 respectively]. CTLA4-318C:49A:(AT)(82) was the most represented haplotype in the studied population and was associated with NHL (P = 0.0029, OR = 1.76, 95% CI = 1.2-2.5). Strong linkage disequilibrium was detected between CD28, CTLA4 and ICOS and a 'common' haplotype was found very frequently among NHLs. However, no independent association between CD28, ICOS, D2S72 markers and NHL was observed. Our findings enable CTLA4 from adjacent functionally related genes as the true causative risk gene for NHL susceptibility at least in Sardinian patients.

Genetics in coeliac disease

Coeliac disease has a strong genetic component, higher than for many other common complex diseases. Possession of the HLA-DQ2 variant is required for presentation of disease causing dietary antigens to T cells, although this is also common in the healthy population. Non-HLA genetic factors account for the majority of heritable risk. Linkage studies have identified promising regions on chromosomes 5 and 19, with multiple other loci awaiting definitive confirmation in independent studies. Inherited variants in the tightly clustered chromosome 2q CD28-CTLA4-ICOS region are associated with disease, although of weak effect size. Larger sample sizes are necessary in coeliac disease genetic studies to detect small effects, alternatively meta-analysis offers promise. Newer methods including gene expression analysis and genome wide association studies will advance understanding of genetic susceptibility. Identification of coeliac disease genes may improve diagnostic/prognostic markers, basic understanding of disease aetiology, permit development of novel therapeutics and provide insight into other autoimmune disorders.

Advances in celiac disease

PURPOSE OF REVIEW

This article aims to summarize recent critical research in celiac disease.

RECENT FINDINGS

The crucial epitopes that confer toxicity to gliadin and related prolamins continue to be defined, as do methods of assessing their toxicity. New approaches to making the gluten-free diet more palatable are being studied.

SUMMARY

The position of proline residues is critical to the toxicity of cereal proteins to patients with celiac disease. Other genetic factors, apart from HLA status, remain elusive. Exciting advances in altering the toxicity of cereal proteins are being made.

Cytokine Gene Polymorphisms and Genetic Association with Coeliac Disease in the Finnish Population

Coeliac disease (CD) is an intestinal disorder caused by intolerance to dietary gluten in susceptible individuals. The HLA-DQ genes are major risk factors for CD, but other genes also play an important role in the disease susceptibility. Immune-mediated mechanisms are known to underlie the pathogenesis of CD. We studied single-nucleotide polymorphisms in transforming growth factor (TGF)-beta1, interleukin (IL)-10, IL-6, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha genes in the Finnish population using family-based association approach. In addition, we genotyped a trinucleotide repeat polymorphism in the major histocompatibility complex (MHC) class I chain-related protein A (MICA) gene, located in the human leucocyte antigen (HLA) region in the vicinity of TNF-alpha. To control the effect of linkage disequilibrium between HLA-DQ genes and MICA and TNF-alpha, an HLA-stratified association analysis was performed. We did not find evidence of association between TGF-beta1, IL-10, IL-6 and IFN-gamma polymorphisms and CD susceptibility. No association was found for any of the MICA alleles independently of DQ genes, whereas TNF-alpha-308 A allele was slightly overrepresented on chromosomes carried by CD patients compared with control chromosomes, indicating that either TNF-alpha, or another gene in linkage disequilibrium with it, could confer increased susceptibility to CD. This result supports the earlier findings that the HLA region harbours a novel susceptibility factor in addition to HLA-DQ.

Genetic analysis of the CD28/CTLA4/ICOS (CELIAC3) region in coeliac disease

In order to extend our previous findings of genetic linkage to the CD28/CTLA4/ICOS region on chromosome 2q33 (CELIAC3) in coeliac disease (CD), we have investigated 22 genetic markers in 325 Norwegian/Swedish multiplex and simplex CD families. We found both linkage and association with several markers, primarily in the multiplex material. We observed strong linkage disequilibrium (LD) between SNPs (Single Nucleotide Polymorphisms) within an LD block delimited by MH30 and D2S72. A haplotype of this region marked by the alleles -1147*T: + 49*A:CT60*G:CT61*A was significantly associated with CD, suggesting that one or more polymorphisms of this haplotype, possibly -1147*T, are involved in CD susceptibility. The CT60 SNP, a polymorphism found to be most strongly associated with some other immune-mediated diseases, was not associated with CD, as this SNP was part of both associated and non-associated haplotypes. Moreover, our results suggest that CELIAC3 harbours several independent loci contributing to CD susceptibility.