HLA and celiac disease susceptibility: new genetic factors bring open questions about the HLA influence and gene-dosage effects.

Celiac disease (CD) is a chronic inflammatory disorder triggered after gluten ingestion in genetically susceptible individuals. The major genetic determinants are HLA-DQA1*05 and HLA-DQB1*02, which encode the DQ2 heterodimer. These alleles are commonly inherited in cis with DRB1*03∶01, which is associated with numerous immune-related disorders, in some cases contributing with a different amount of risk depending on the haplotype context. We aimed at investigating those possible differences involving DRB1*03∶01-carrying haplotypes in CD susceptibility. A family (274 trios) and a case-control sample (369 CD cases/461 controls) were analyzed. DRB1*03∶01-carrying individuals were classified according to the haplotype present (ancestral haplotype (AH) 8.1, AH 18.2 or non-conserved haplotype) after genotyping of HLA-DRB1, -DQA1, -DQB1, -B8, TNF -308, TNF -376 and the TNFa and TNFb microsatellites. We observe that the AH 8.1 confers higher risk than the remaining DRB1*03∶01-carrying haplotypes, and this effect only involves individuals possessing a single copy of DQB1*02. CD risk for these individuals is similar to the one conferred by inherit DQA1*05 and DQB1*02 in trans. It seems that an additional CD susceptibility factor is present in the AH 8.1 but not in other DRB1*03∶01-carrying haplotypes. This factor could be shared with individuals possessing DQ2.5 trans, according to the similar risk observed in those two groups of individuals.

Th17-related genes and celiac disease susceptibility.

Th17 cells are known to be involved in several autoimmune or inflammatory diseases. In celiac disease (CD), recent studies suggest an implication of those cells in disease pathogenesis. We aimed at studying the role of genes relevant for the Th17 immune response in CD susceptibility. A total of 101 single nucleotide polymorphisms (SNPs), mainly selected to cover most of the variability present in 16 Th17-related genes (IL23R, RORC, IL6R, IL17A, IL17F, CCR6, IL6, JAK2, TNFSF15, IL23A, IL22, STAT3, TBX21, SOCS3, IL12RB1 and IL17RA), were genotyped in 735 CD patients and 549 ethnically matched healthy controls. Case-control comparisons for each SNP and for the haplotypes resulting from the SNPs studied in each gene were performed using chi-square tests. Gene-gene interactions were also evaluated following different methodological approaches. No significant results emerged after performing the appropriate statistical corrections. Our results seem to discard a relevant role of Th17 cells on CD risk.

Association between shared epitope and anti-citrullinated peptide antibodies in rheumatoid arthritis: A systematic review and meta-analysis

The group of major histocompatibility complex (MHC) alleles known as shared epitope (SE)is to date the strongest rheumatoid arthritis (RA) genetic risk factor. Many studies have shown that the measurement of anti-citrullinated peptides antibodies would be useful in the diagnosis and follow-up of RA. Our aim is to determine the magnitude of the association between the possession of SE alleles and serum positive titres of antibodies against citrullinated peptides. Our selection criteria included case–control or cohort studies, where data involving antibodies against citrullinated peptides and SE in RA patients were available. No date or language restrictions were imposed. Bibliographical databases MEDLINE, Cochrane Database of Systematic Reviews and EMBASE were searched for pertinent literature. Two reviewers independently identified relevant citations and extracted data. Data extraction was then checked by two different reviewers. Five published and one unpublished (own data) studies were included in the final metaanalysis. Overall, 2700 European descent RA patients were included in this meta-analysis. A significant association between SE and positive titres of serum antibodies against citrullinated peptides [OR(95% CI) = 3.19 (2.21–4.60)] was found. Positive titres for antibodies against citrullinated peptides are threefold more frequent in RA patients who carry SE alleles than in those patients lacking them (AU)

El grupo de alelos del complejo mayor de histocompatibilidad (MHC) conocidos como epí-topo compartido (EC) es a día de hoy el más fuerte los factores de riesgo genético a artritisreumatoide (AR). Diferentes estudios han puesto de manifiesto que la presencia de autoanticuerpos contra péptidos citrulinados sería útil en el diagnóstico y seguimiento de la artritisreumatoide. Nuestro objetivo es determinar la magnitud de la asociación entre la posesión de alelos del SE y la presencia de títulos positivos de anticuerpos contra péptidos citrulinados. Nuestros criterios de selección incluyeron estudios de cohortes y caso-control en los que hubiera datos disponibles acerca de los anticuerpos contra péptidos citrulinados y el epítopo compartido en artritis reumatoide. No se hicieron restricciones de fecha ni de idioma. Se realizaron búsquedas en las bases de datos bibliográficas MEDLINE, Cochrane Database of Systematic Reviews y EMBASE. Dos revisores identificaron de manera independiente lascitas relevantes y extrajeron los datos. La extracción de datos fue comprobada posteriormente por dos revisores diferentes de los anteriores. En el meta-análisis definitivo se incluyeron cinco estudios publicados y uno no publicado(datos propios). En total se incluyeron 2700 casos de RA de ascendencia europea en el metaanálisis. Se encontró una asociación significativa entre los títulos de anticuerpos positivos y el hecho de ser portador de alelos del epítopo compartido [OR(95% CI) = 3.19 (2.21–4.60)]. Los títulos positivos de anticuerpos contra péptidos citrulinados son tres veces más frecuentes en pacientes de AR portadores de alelos del EC que en los no portadores (AU)

Study of polymorphisms in 4q27, 10p15, and 22q13 regions in autoantibodies stratified type 1 diabetes patients.

Type 1 diabetes (T1D) is a multifactorial disease mainly associated with the human leukocyte antigen region. Previous studies suggested the association of interleukin-2 (IL2) gene polymorphisms and its alpha- and beta-chain receptor (IL2RA and IL2RB) variants with different autoimmune diseases such as T1D, celiac disease, multiple sclerosis, and rheumatoid arthritis. All T1D studies were conducted in diabetic patients younger than 17 years at diagnosis. The aim of our study was to replicate these associations not only in pediatric patients, but also in individuals with late onset. We performed a genetic association study of chromosomal regions 4q27, 10p15, and 22q13 containing the IL2, IL2RA, and IL2RB genes in 445 T1D subjects and 828 healthy controls. Seven single nucleotide polymorphisms (SNPs) were selected, previously described as genetic factors related to several autoimmune diseases, and were analyzed by TaqMan assays. The reported association with T1D patients of the IL2RA-rs41295061 located in the 10p15 region was replicated and our data suggest a trend of association of the polymorphisms IL2-rs17388568 and IL2-rs6822844 in 4q27. The effect of these markers was independent of the age at disease onset. Furthermore, the polymorphisms studied in 4q27 were not dependent on the presence of autoantibodies; however, the effect of the associated SNP in 10p15 (IL2RA-rs41295061) was specific of patients sera positive for diabetes antibodies. In conclusion, our results seem to indicate that late-onset and young T1D patients share most genetic factors located in the studied regions, but some markers could correlate with the presence of T1D specific autoantibodies.

Lack of association of NKX2-3, IRGM, and ATG16L1 inflammatory bowel disease susceptibility variants with celiac disease.

Evidence about the presence of susceptibility factors shared among different autoimmune diseases is increasing. Based on this idea, NKX2-3, ATG16L1, and IRGM which are well-established inflammatory bowel disease risk factors, could be new celiac disease (CD) candidate genes. NKX2-3 encodes a transcription factor that in mice seems to be involved in gut development. The ATG16L1 and IRGM genes act in autophagy, a process related to innate and adaptive immunity. We aimed to study the implication of five polymorphisms in these genes in CD susceptibility: rs10883365 and rs888208 in the NKX2-3 gene, rs2241880 in ATG16L1, and rs10065172 and rs4958847 in IRGM. Association studies were performed using 725 Spanish CD patients and 956 ethnically matched healthy controls, as well as 309 parent-child trios. Genetic frequencies were compared with the chi(2) test and the familial study used the transmission disequilibrium test. Differences between CD patients and controls did not reach significance when genotypic and allelic frequencies were compared. No differential transmission of alleles or haplotypes from heterozygous parents to affected children was observed in the familial study. In conclusion, no evidence of association with CD has been reported for the Crohn's disease susceptibility polymorphisms studied in the NKX2-3, ATG16L1, and IRGM genes.

The IL6-174G/C polymorphism is associated with celiac disease susceptibility in girls.

The aim of this paper was to study the role of IL6 and IL6R polymorphisms in celiac disease (CD) susceptibility. Because previous literature describes IL-6-related gender differences, sex-stratified analyses were performed. We undertook a case-control study with 374 pediatric CD patients and 853 healthy controls, all white Spaniards, and a family study using an independent sample including 303 trios for replication purposes. Three single-nucleotide polymorphisms tagging most of the variability of the IL6 gene (rs2069827, rs1800795 [-174G/C], and rs2069840) and one functional polymorphism in IL6R (rs8192284, Asp358Ala) were genotyped using TaqMan technology. Case-control comparisons were performed with the chi2 test and family data were analyzed with the transmission disequilibrium test. No association was observed between any tested polymorphism and overall CD. However, after sex stratification, we found that the IL6 promoter variant -174C increases the risk of developing CD specifically in female patients. This effect was observed both in the case-control and in the family studies (considering girls included in both studies vs boys: p = 0.021, odds ratio [OR] = 1.31, 95% confidence interval [CI] 1.03-1.66; and vs controls: p = 0.003, OR = 1.30, 95% CI 1.09-1.55). The functional -174G/C IL6 polymorphism seems to influence CD susceptibility in girls. The gender-specific role of IL-6 in this pathology must be further investigated.

IL4 in the 5q31 context: association studies of type 1 diabetes and rheumatoid arthritis in the Spanish population.

IL4, the gene coding the prototypic Th2 cytokine, has been frequently studied in the context of several inflammatory conditions, but conclusive results have not been obtained. This gene is located in the 5q31-33 complex genetic region, which shows some susceptibility factors to type 1 diabetes (T1D) and rheumatoid arthritis (RA) among other inflammatory conditions. Our aim was to assess the involvement on T1D and RA of IL4 polymorphisms considered individually and in combination with other polymorphisms in 5q31-33, specifically in the OCTN locus, where the L503F polymorphism has been associated with Crohn's disease and other Th1 diseases. We performed a case-control study including 316 T1D patients, 599 RA patients and 540 healthy controls, all of them corresponding to white Spanish individuals. The IL4 single-nucleotide polymorphisms (SNPs) -590C/T (rs2243250) and the OCTN1 exonic SNP L503F (rs1050152) were analysed in all samples. Frequency comparisons of -590C/T and stratified analysis including both cited SNPs were performed using chi-square tests. The -590C/T IL4 SNP was not found associated with T1D or RA when individual analyses were performed. However, a significant association with T1D emerged after stratification by L503F [p=0.02, odds ratio=1.95, 95% CI=1.07-3.55]. The location of the IL4 gene in the complex 5q31-33 genetic region, which contains many genes involved in immunological responses and presents linkage disequilibrium extended along many kilobases, makes necessary to interpret cautiously the previous IL4-association studies.

Gender-specific association of the PTPN22 C1858T polymorphism with achalasia.

The protein tyrosine phosphatase N22 (PTPN22) gene encodes a lymphoid-specific phosphatase (LYP), a downregulator of T-cell activation. Because a functional PTPN22 polymorphism, C1858T, has been found to be associated with different autoimmune diseases, we aimed to elucidate the role of this variant in predisposition to achalasia. We performed a case-control study with 231 nonrelated Spanish patients of white ethnicity diagnosed with achalasia and in 554 healthy control subjects, all genotyped for PTPN22 C1858T using TaqMan chemistry. The frequency of the 1858T allele was higher in the achalasia patients than in the healthy controls (carriers of allele T vs CC: OR = 1.38, 95% confidence interval [95% CI] 0.88-2.16, p = 0.13). Moreover a different genotype distribution was found between female and male patients (carriers of allele T vs CC: OR = 2.06, 95% CI 0.96-4.42, p = 0.04) and also between female patients and controls (OR = 1.94, 95% CI 1.12-3.36, p = 0.01), but not between male patients and controls (OR = 0.94, 95% CI 0.50-1.77, p = 0.85). We conclude that the PTPN22 1858T allele is a susceptibility factor for Spanish women with achalasia.

Susceptibility to type 1 diabetes conferred by the PTPN22 C1858T polymorphism in the Spanish population.

BACKGROUND: The protein tyrosine phosphatase N22 gene (PTPN22) encodes a lymphoid-specific phosphatase (LYP) which is an important downregulator of T cell activation. A PTPN22 polymorphism, C1858T, was found associated with type 1 diabetes (T1D) in different Caucasian populations. In this study, we aimed at confirming the role of this variant in T1D predisposition in the Spanish population. METHODS: A case-control was performed with 316 Spanish white T1D patients consecutively recruited and 554 healthy controls, all of them from the Madrid area. The PTPN22 C1858T SNP was genotyped in both patients and controls using a TaqMan Assay in a 7900 HT Fast Real-Time PCR System. RESULTS: We replicated for the first time in a Spanish population the association of the 1858T allele with an increased risk for developing T1D [carriers of allele T vs. CC: OR (95%) = 1.73 (1.17-2.54); p = 0.004]. Furthermore, this allele showed a significant association in female patients with diabetes onset before age 16 years [carriers of allele T vs. CC: OR (95%) = 2.95 (1.45-6.01), female patients vs female controls p = 0.0009]. No other association in specific subgroups stratified for gender, HLA susceptibility or age at onset were observed. CONCLUSION: Our results provide evidence that the PTPN22 1858T allele is a T1D susceptibility factor also in the Spanish population and it might play a different role in susceptibility to T1D according to gender in early-onset T1D patients.

Evidence for the association of the SLC22A4 and SLC22A5 genes with type 1 diabetes: a case control study.

BACKGROUND: Type 1 diabetes (T1D) is a chronic, autoimmune and multifactorial disease characterized by abnormal metabolism of carbohydrate and fat. Diminished carnitine plasma levels have been previously reported in T1D patients and carnitine increases the sensitivity of the cells to insulin. Polymorphisms in the carnitine transporters, encoded by the SLC22A4 and SLC22A5 genes, have been involved in susceptibility to two other autoimmune diseases, rheumatoid arthritis and Crohn's disease. For these reasons, we investigated for the first time the association with T1D of six single nucleotide polymorphisms (SNPs) mapping to these candidate genes: slc2F2, slc2F11, T306I, L503F, OCTN2-promoter and OCTN2-intron. METHODS: A case-control study was performed in the Spanish population with 295 T1D patients and 508 healthy control subjects. Maximum-likelihood haplotype frequencies were estimated by applying the Expectation-Maximization (EM) algorithm implemented by the Arlequin software. RESULTS: When independently analyzed, one of the tested polymorphisms in the SLC22A4 gene at 1672 showed significant association with T1D in our Spanish cohort. The overall comparison of the inferred haplotypes was significantly different between patients and controls (chi2 = 10.43; p = 0.034) with one of the haplotypes showing a protective effect for T1D (rs3792876/rs1050152/rs2631367/rs274559, CCGA: OR = 0.62 (0.41-0.93); p = 0.02). CONCLUSION: The haplotype distribution in the carnitine transporter locus seems to be significantly different between T1D patients and controls; however, additional studies in independent populations would allow to confirm the role of these genes in T1D risk.