MHC class I chain related gene A (MICA) modulates the development of coeliac disease in patients with the high risk heterodimer DQA1*0501/DQB1*0201

Immune evasion by proteolytic shedding of natural killer group 2, member D ligands in Helicobacter pylori infection

Background

Helicobacter pylori (H. pylori) uses various strategies that attenuate mucosal immunity to ensure its persistence in the stomach. We recently found evidence that H. pylori might modulate the natural killer group 2, member 2 (NKG2D) system. The NKG2D receptor and its ligands are a major activation system of natural killer and cytotoxic T cells, which are important for mucosal immunity and tumor immunosurveillance. The NKG2D system allows recognition and elimination of infected and transformed cells, however viruses and cancers often subvert its activation. Here we aimed to identify a potential evasion of the NKG2D system in H. pylori infection.

Methods

We analyzed expression of NKG2D system genes in gastric tissues of H. pylori gastritis and gastric cancer patients, and performed cell-culture based infection experiments using H. pylori isogenic mutants and epithelial and NK cell lines.

Results

In biopsies of H. pylori gastritis patients, NKG2D receptor expression was reduced while NKG2D ligands accumulated in the lamina propria, suggesting NKG2D evasion. In vitro, H. pylori induced the transcription and proteolytic shedding of NKG2D ligands in stomach epithelial cells, and these effects were associated with specific H. pylori virulence factors. The H. pylori-driven release of soluble NKG2D ligands reduced the immunogenic visibility of infected cells and attenuated the cytotoxic activity of effector immune cells, specifically the anti-tumor activity of NK cells.

Conclusion

H. pylori manipulates the NKG2D system. This so far unrecognized strategy of immune evasion by H. pylori could potentially facilitate chronic bacterial persistence and might also promote stomach cancer development by allowing transformed cells to escape immune recognition and grow unimpeded to overt malignancy.

HLA-DQ2/8 and COVID-19 in Celiac Disease: Boon or Bane

The SARS-CoV-2 pandemic continues to pose a global threat. While its virulence has subsided, it has persisted due to the continual emergence of new mutations. Although many high-risk conditions related to COVID-19 have been identified, the understanding of protective factors remains limited. Intriguingly, epidemiological evidence suggests a low incidence of COVID-19-infected CD patients. The present study explores whether their genetic background, namely, the associated HLA-DQs, offers protection against severe COVID-19 outcomes. We hypothesize that the HLA-DQ2/8 alleles may shield CD patients from SARS-CoV-2 and its subsequent effects, possibly due to memory CD4 T cells primed by previous exposure to human-associated common cold coronaviruses (CCC) and higher affinity to those allele's groove. In this context, we examined potential cross-reactivity between SARS-CoV-2 epitopes and human-associated CCC and assessed the binding affinity (BA) of these epitopes to HLA-DQ2/8. Using computational methods, we analyzed sequence similarity between SARS-CoV-2 and four distinct CCC. Of 924 unique immunodominant 15-mer epitopes with at least 67% identity, 37 exhibited significant BA to HLA-DQ2/8, suggesting a protective effect. We present various mechanisms that might explain the protective role of HLA-DQ2/8 in COVID-19-afflicted CD patients. If substantiated, these insights could enhance our understanding of the gene-environment enigma and viral-host relationship, guiding potential therapeutic innovations against the ongoing SARS-CoV-2 pandemic.

Search for Genetic Predictors of Adult Autoimmune Polyendocrine Syndrome in Monozygotic Twins

Autoimmune polyendocrine syndromes (APS) are a heterogeneous group of diseases characterized by the presence of autoimmune dysfunction of 2 or more endocrine glands and other non-endocrine organs. The components of the syndrome can manifest throughout life: in childhood—APS type 1 (the juvenile type) and in adulthood—APS type 2, 3, and 4 (the adult types). Adult types of APS are more common in clinical practice. It is a polygenic disease associated with abnormalities in genes encoding key regulatory proteins of the major histocompatibility complex (MHC). The search of for candidate genes responsible for mutations in adult APS is continuing. Genetic predisposition is insufficient for the manifestation of the APS of adults, since the penetrance of the disease, even among monozygotic twins, does not approach 100% (30–70%). The article presents the case of isolated Addison’s disease and APS type 2 in monozygotic twins with a revealed compound heterozygosity in the candidate gene VTCN1.

Prevalance of Celiac Disease in Patients with Inflammatory Bowel Disease in Turkish Population

Background

Celiac disease (CD) and inflammatory bowel disease (IBD) involve inflammation of the gastrointestinal lumen, which environmental, genetic, and immunological factors have a role in their pathogenesis. The prevalence of celiac disease in IBD ranges from 0% to 14%. In this study, our aim was to determine the prevalence of CD in IBD patients followed by us who are attending the hospital or outpatient clinic over a period of time of seven years.

Methods

Seven hundred and fifty nine patients (425 M, 334 F, mean age: 46.75, 396 ulcerative colitis (UC), 363 Crohn's disease (CrD)) diagnosed and followed up for IBD between January 2009 and July 2016 were evaluated retrospectively, and clinical, demographic, laboratory, and endoscopic data were collected.

Results

CD was investigated in 79 (%10.4) inflammatory bowel disease patients according to symptoms, and in 5.06% (n = 4) of them, we diagnosed CD. The most common indication for investigating for CD was iron deficiency anemia unreponsive to iron supplementation.

Conclusions

We did not find an increased prevalance of celiac disease in Turkish IBD patients in this study. In the presence of refractory iron deficiency anemia without any other cause in IBD patients, investigations for celiac disease should be considered.

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.

Overview of biomarkers for diagnosis and monitoring of celiac disease

Among the adverse reactions caused by wheat, celiac disease (CD) is the longest studied and best-known pathology. The more recently defined non-celiac gluten sensitivity (NCGS) presents with symptoms which are often indistinguishable from CD. Diagnosis of CD is based on serologic, molecular, and bioptic testing. The IgA anti-transglutaminase (tTG) test is considered highly important, as it shows high sensitivity and specificity and its levels correlate to the degree of intestinal damage. Small bowel biopsy can be avoided in symptomatic patients with IgA anti-tTG levels above 10× the manufacturer's cut-off. Recently, tests of anti-deamidated peptides of gliadin (DGP) have replaced classic anti-native gliadin (AGA) tests. DGP assays have a considerably higher diagnostic accuracy than AGA assays, especially in the IgG class, and can replace anti-tTG tests in patients with selective IgA deficiency. The combination of IgG anti-DGP plus IgA anti-tTG assays show greater sensitivity than a single test, with very high specificity. EMA tests have great diagnostic accuracy but are not recommended by all the latest guidelines because they are observer dependent. Biopsy must still be considered the gold standard for CD diagnosis. HLA-DQ genotyping can be used to screen asymptomatic children and in cases of histology/serology disagreement. About half of NCGS patients are DQ2 positive and have IgG AGA. To diagnose NCGS, first CD and wheat allergy must be excluded; then the wheat dependence of symptoms must be verified by a gluten-free diet and subsequent gluten challenge.

Immunogenetic biomarkers in inflammatory bowel diseases: Role of the IBD3 region

Many studies have demonstrated the linkage between the IBD3 region (6p21.1-23), an area which encompasses the famous human leukocyte antigen (HLA) complex, and Crohn’s disease (CD) or ulcerative colitis (UC). IBD3 is the only region that meets genome-wide significance, and provides stronger evidence of the linkage than 16p13.1-16q12.2 (IBD1), the locus that contains the susceptibility gene CARD15. However, despite these findings, IBD3 susceptibility genes remain elusive and unclear due to the strong linkage disequilibrium, extensive polymorphism, and high gene density that characterize this area and also due to varying allele frequencies in populations around the world. This area presents an extremely high abundance of genes, including the classical and non-classical major histocompatibility complex (MHC) class I and II genes, and other genes, namely MHC class III genes tumor necrosis factor (TNF)-α and -β, and Hsp, whose proteins play key functions in immunological processes. To date, it is not clear which genes within the MHC family contribute to the IBD pathogenesis, although certain HLA alleles have been associated with IBD. Recent insights into the biological function of other genes encoded within the IBD3 region, such as the MHC class I chain-related (MIC) genes, have led investigators to a more comprehensive exploration of this region. MHC class I chain-related molecule A (MICA) is highly polymorphic and interacts with NKG2D, its receptor on the surface of NK, Tγδ and T CD8⁺ cells. Increased expression of MICA in intestinal epithelial cells and increased expression of NKG2D in CD4⁺ T cells (lamina propria) in patients with CD have also been reported. MICA alleles have also been associated with IBD, and a variation at amino acid position 129 of the α2-heavy chain domain seems to categorize MICA alleles into strong and weak binders of NKG2D receptor, thereby influencing the effector cells’ function. In this regard, a relevant role of MICA-129-Val/Met single nucleotide polymorphism has recently been implicated in the pathogenesis of IBD. TNF-α and -β also play an important role in inflammatory response. In fact, IBD is commonly treated with TNF-α inhibitors. Additionally, polymorphisms of TNF-α gene are known to affect the gene expression level and particular TNF-α genotypes may influence the response of IBD patients treated with TNF-α inhibitors.

Diversity and characterization of polymorphic 5' promoter haplotypes of MICA and MICB genes

The major histocompatibility complex (MHC) class I-related chain A (MICA) and B (MICB) are ligands for the natural killer group 2, member D (NKG2D) activating receptor expressed on natural killer (NK) cells, natural killer T (NKT) cells, CD8+ T cells and γδ T cells. Natural killer group 2, member D (NKG2D) ligand expression is stress-related and upregulated by infected or oncogenic cells leading to cytolysis. MICA and MICB genes display considerable polymorphism among individuals and studies have investigated allelic association with disease and relevance of MICA in transplantation, with variable success. It is now known that promoters of MICA and MICB are polymorphic with some polymorphisms associating with reduced expression. We sequenced International Histocompatibility Workshop (IHW) cell line DNA to determine promoter types and alleles encoded by exons 2-6. We found 8 of 12 known MICA promoter polymorphisms and although promoter P7 dominated, other promoters associated with the same allele. For example, MICA*002:01 had promoters P3, P4 or P7 and the common MICA*008:01/04 type had P1, P6 or P7. Similarly, we sequenced 8 of 12 known MICB promoter haplotypes. Some coding region defined MICB alleles had a single promoter, for example, MICB*002:01 and promoter P9, whereas the promiscuous MICB*005 allele had promoters P1, P2, P5, P6, P10 or P12. The results indicate potential for variation in expression of MICA and MICB ligands between individuals with the same allelic types. If differential expression by polymorphic MICA and MICB promoters is confirmed by functional studies, involvement of these genes in disease susceptibility or adverse transplantation outcomes may require knowledge of both promoter and allelic types to make meaningful conclusions.

Autoantibodies against MHC class I polypeptide-related sequence A are associated with increased risk of concomitant autoimmune diseases in celiac patients

BACKGROUND

Overexpression of autologous proteins can lead to the formation of autoantibodies and autoimmune diseases. MHC class I polypeptide-related sequence A (MICA) is highly expressed in the enterocytes of patients with celiac disease, which arises in response to gluten. The aim of this study was to investigate anti-MICA antibody formation in patients with celiac disease and its association with other autoimmune processes.

METHODS

We tested serum samples from 383 patients with celiac disease, obtained before they took up a gluten-free diet, 428 patients with diverse autoimmune diseases, and 200 controls for anti-MICA antibodies. All samples were also tested for anti-endomysium and anti-transglutaminase antibodies.

RESULTS

Antibodies against MICA were detected in samples from 41.7% of patients with celiac disease but in only 3.5% of those from controls (P <0.0001) and 8.2% from patients with autoimmune disease (P <0.0001). These antibodies disappeared after the instauration of a gluten-free diet. Anti-MICA antibodies were significantly prevalent in younger patients (P <0.01). Fifty-eight patients with celiac disease (15.1%) presented a concomitant autoimmune disease. Anti-MICA-positive patients had a higher risk of autoimmune disease than MICA antibody-negative patients (P <0.0001; odds ratio = 6.11). The risk was even higher when we also controlled for age (odds ratio = 11.69). Finally, we found that the associated risk of developing additional autoimmune diseases was 16 and 10 times as high in pediatric patients and adults with anti-MICA, respectively, as in those without.

CONCLUSIONS

The development of anti-MICA antibodies could be related to a gluten-containing diet, and seems to be involved in the development of autoimmune diseases in patients with celiac disease, especially younger ones.

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.

Association study of MICA-TM polymorphism with inflammatory bowel disease in the South Tunisian population

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory disorders of the gastro-intestinal tract with unknown etiology. Both environmental and genetic factors are involved in the pathogenesis of these inflammatory bowel diseases (IBD).

AIM

The purpose of the present study was to determine the association between the polymorphism of the transmembrane region of MICA (MICA-TM), and the genetic susceptibility in Tunisian patients with IBD.

PATIENTS AND METHODS

A total of 102 Tunisian patients (66 with UC, 36 with CD) and 123 healthy controls were enrolled in our study. MICA-TM was genotyped by a semiautomatic fluorescent-labelled PCR method, amplicons were analysed on an ABI Prism 310 genotyper. Comparisons of allele frequencies between patients and controls, and between patients' subgroups were performed using SPSS 13.0.

RESULTS

No MICA allele was significantly increased in both groups of IBD compared to controls. The MICA-A5.1 allele was significantly decreased in CD patients (p=0.006, pc=0.03). In UC, MICA-A6 was associated with the presence of extraintestinal manifestations (p=0.04, pc=0.2), whereas MICA-A5 was associated with late age of onset (p=0.04). In CD, MICA-A6 was significantly increased in active disease patients when compared to moderately active or inactive disease (p=0.03, pc=0.15).

CONCLUSION

Some clinical features of CD and UC may be influenced by specific MICA-TM alleles. In our South Tunisian population, MICA plays a disease modifying role, rather than being an important gene in the susceptibility for developing IBD.

Atypical celiac disease: from recognizing to managing. Gastroenterol Res Pract. 2012;2012:637187. [PMID: 22811701 PMCID: PMC3395124 DOI: 10.1155/2012/637187]

The nonclassic clinical presentation of celiac disease (CD) becomes increasingly common in physician's daily practice, which requires an awareness of its many clinical faces with atypical, silent, and latent forms. Besides the common genetic background (HLA DQ2/DQ8) of the disease, other non-HLA genes are now notably reported with a probable association to atypical forms. The availability of high-sensitive and specific serologic tests such as antitissue transglutuminase, antiendomysium, and more recent antideamidated, gliadin peptide antibodies permits to efficiently uncover a large portion of the submerged CD iceberg, including individuals having conditions associated with a high risk of developing CD (type 1 diabetes, autoimmune diseases, Down syndrome, family history of CD, etc.), biologic abnormalities (iron deficiency anemia, abnormal transaminase levels, etc.), and extraintestinal symptoms (short stature, neuropsychiatric disorders, alopecia, dental enamel hypoplasia, recurrent aphtous stomatitis, etc.). Despite the therapeutic alternatives currently in developing, the strict adherence to a GFD remains the only effective and safe therapy for CD.

Clinical profile of coexisting conditions in type 1 diabetes mellitus patients

AIMS

Type 1 diabetes mellitus (T1DM) is associated with various genetic and autoimmune diseases implicated in its etiopathogenesis. We hereby profile the clinical association of such diseases among patients from our center.

METHODS

Consecutive patients of T1DM presenting to department of Endocrinology from May 1997 to December 2011 were retrospectively analyzed in context of associated clinical profile.

RESULTS

Among 260 patients diagnosed as T1DM, 21 (8%) had hypothyroidism, 4 (1.5%) had hyperthyroidism and 2 (0.7%) had primary adrenal insufficiency. Eighteen patients (7%) had celiac disease, 9 (3.5%) had Turner's syndrome, 5 patients (1.9%) had Klinefelter's syndrome, whereas Down's syndrome and Noonan's syndrome was present in 2 and 1 patients (0.7%) respectively. One patient had Wolframs' syndrome and 1 patients had myasthenia gravis. Systemic lupus erythematosus and rheumatoid arthritis were present in 3 and 1 patients respectively. Total of 5 patients with cerebral palsy, 4 cases with deaf mutism, 4 cases with acute psychosis and 16 patients with depression were noted. Mean age of study patients was 20.8±9.8 years (range, 3-23 years).

CONCLUSION

Various conditions including genetic (Down, Turner, Noonan, and Klinefelter's), autoimmune (thyroid and adrenal disorders, myasthenia gravis, SLE, rheumatoid arthritis) and central nervous system diseases were the associated diseases encountered in our patients. Routine screening is required for early diagnosis and treatment of associated co morbidities.

HLA and MICA genes in patients with tuberculosis in Brazil

Major histocompatibility complex (MHC) genes have been investigated because of their crucial role in the defense against pathogens and their high degree of polymorphism. We performed a case-control study to assess a genetic association of MHC genes with susceptibility to tuberculosis (TB). The allelic lineages HLA-A*02 and B*18 were significantly less frequent in TB patients (n = 112, 44.6% women) than in controls (n = 224, 51.5% women): 18.8% vs 26.5%; odds ratio (OR) = 0.64; P = 0.037 and 2.7% vs 6.9%; OR = 0.37; P = 0.041. The negative association with haplotype HLA-B*18-MICA*018 (2.3% patients vs 6.4% controls; OR = 0.34; P = 0.035) was significant as a consequence of strong linkage disequilibrium (D' = 0.827 for patients and 0.923 for controls). These findings suggest a trend toward protection of the HLA-A*02 and HLA-B*18 alleles.

Prevalence of celiac disease in multiple sclerosis

BACKGROUND

Celiac disease (CD) is a common systemic disease related to a permanent intolerance to gluten and is often associated with different autoimmune and neurological diseases. Its mean prevalence in the general population is 1-2% worldwide. Our aim was to study the prevalence of celiac disease in a prospective series of Multiple Sclerosis (MS) patients and their first-degree relatives.

METHODS

We analyzed the prevalence of serological, histological and genetic CD markers in a series of 72 MS patients and in their 126 first-degree relatives, compared to 123 healthy controls.

RESULTS

Tissue IgA-anti-transglutaminase-2 antibodies were positive in 7 MS patients (10%), compared to 3 healthy controls (2.4%) (p < 0.05). OR: 5.33 (CI-95%: 1.074-26.425). No differences were found in HLA-DQ2 markers between MS patients (29%) and controls (26%) (NS).We detected mild or moderate villous atrophy (Marsh III type) in duodenal biopsies, in 8 MS patients (11.1%). We also found a high proportion of CD among first-degree relatives: 23/126 (32%). Several associated diseases were detected, mainly dermatitis 41 (57%) and iron deficiency anemia in 28 (39%) MS patients. We also found in them, an increased frequency of circulating auto-antibodies such as anti-TPO in 19 (26%), ANA in 11 (15%) and AMA in 2 (3%).

CONCLUSIONS

We have found an increased prevalence of CD in 8 of the 72 MS patients (11.1%) and also in their first-degree relatives (23/126 [32%]). Therefore, increased efforts aimed at the early detection and dietary treatment of CD, among antibody-positive MS patients, are advisable.

An influence of HLA-A, B, DR, DQ, and MICA on the occurrence of Celiac disease in patients with type 1 diabetes

Celiac disease (CD) is more common in individuals with insulin dependent diabetes mellitus (T1D) than in the general population. HLA class II molecules DQ8 (DQB1*0302-DQA1*0301) and DQ2 (DQB1*0201-DQA1*0501) have been identified as key genetic risk factors in both diseases. While DQ8 conveys a higher risk for T1D, DQ2 is more frequent in CD. Less is known about the contribution of HLA class I. The gut immune system has been implicated in the pathogenesis of both diseases. The MICA, which is mainly expressed in the gastrointestinal epithelium and recognized by gammadeltaT lymphocytes and natural killer (NK) cells via the NKG2D, might play a role. The aim of our study was to identify possible HLA class I and MICA alleles and conserved extended haplotypes as risk factors for the development of CD in T1D. Three groups consisting of 37 individuals with T1D and CD, 67 individuals with only T1D and 70 controls were analyzed. HLA class I and MICA alleles were determined using Luminex technology. An occurrence of CD in individuals with T1D was most significantly associated with B*08 (P = 7.3 x 10(-13)), contributing more than any of the HLA class II alleles (DRB1*0301, P = 5.00 x 10(-10); DQB1*0201, P = 7.65 x 10(-8)). Moreover, the association with CD became stronger when B*08(B*08-DQA*0501-DQB1*0201-DRB1*0301, P = 5.07 x 10(-12)) was present in the DRB1*0301-DQB1*0201-DQA1*0501 (P = 5.00 x 10(-10)) extended haplotype. We suggest a combined influence of alleles present in the MICA*008-B*08-A1-DR3-DQ2 extended haplotype on the development of CD in Slovenian individuals with T1D, where B*08 or/and a gene located close to it may play an important role, independently of HLA class II.

Association analysis of MICA gene polymorphism and MICA-129 dimorphism with inflammatory bowel disease susceptibility in a Spanish population

MICA is located at 46 kb centromeric of HLA-B, is highly polymorphic and interactions with NKG2D, its receptor on the surface of NK, Tgammadelta, and T CD8 lymphocytes. A variation at amino acid position 129 of the alpha2-heavy chain domain seems to categorize MICA alleles into strong and weak binder of NKG2D receptor, and thereby to influence effector cell function. Our aim was to study allele polymorphism of MICA and the functionally relevant dimorphism (129val/met) of MICA gene in inflammatory bowel disease (IBD) patients in our population. DNA was obtained from IBD patients (n = 88) and unrelated healthy Murcians (n = 154) and used to MICA genotyping using polymerase chain reaction-sequence-specific oligonucleotides. We did not find statistical differences in the distribution of MICA alleles between the IBD and control groups. However, we found a higher frequency of MICA-129met/met and a lower frequency of MICA-129val/met genotypes in IBD patients (mainly in ulcerative colitis) than in controls (pc = 0.02). These preliminary data could suggest a relevant role of MICA-129-val/met SNP (weak/strong binders of NKG2D receptor) in the pathogenesis of IBD.

Prevalence of celiac disease in inflammatory bowel diseases: An IG-IBD multicentre study

BACKGROUND

An association has been described in case reports between celiac disease and inflammatory bowel diseases. The aim of the present study is to assess the prevalence of celiac disease in a large series of Italian patients with inflammatory bowel disease.

METHODS

The Italian Group for Inflammatory Bowel Disease conducted a multicentre study between January 2002 and December 2004, in which 22 gastroenterology centres in Italy enrolled 1711 consecutive outpatients with inflammatory bowel disease. 860 (50.2%) had Crohn's disease (415 females, mean age 40, range 18-75), 791 (46.2%) had ulcerative colitis (371 females, mean age 40, range 18-80), and 60 (3.5%) had indeterminate colitis (27 females, mean age 40, range 18-78). All patients underwent serological testing for anti-endomysial antibodies and anti-tissue transglutaminase antibodies; if positive upper GI endoscopy with duodenal biopsy was performed.

RESULTS

Nine of the 1711 patients (0.5%) had serological and histological findings compatible with the diagnosis of celiac disease; six of them had ulcerative colitis and three had Crohn's disease.

CONCLUSIONS

Overall we found a lower risk of celiac disease in our cohort of inflammatory bowel disease patients than in the general population; prevalence of celiac disease was higher in patients with ulcerative colitis than in those with Crohn's disease.

HLA class II polymorphism in children with coeliac disease in Tunisia: is there any influence on clinical manifestation?

OBJECTIVE

To elucidate the HLA DRB1, DQB1 and DQA1 polymorphism in Tunisian children with typical form of coeliac disease (CD) in comparison with those from mass screening (atypical and silent CD).

MATERIALS AND METHODS

We recruited three groups: group I: 40 CD children diagnosed according to the ESPGHAN criteria. group II: 40 healthy controls matched with sex, age and geographic origin. group III: 38 CD children coming from mass screening in schoolchildren. HLA class II DRB1, DQB1 and DQA1 alleles were typed by PCR-sequence-specific primer.

RESULTS

Comparing the groups I and II, we found a pronounced increase of the susceptible alleles HLA DRB1*03 (relative risk, RR = 4.18, Pc = 0.001), DQB1*02 (RR = 7.9, Pc<0.0001) and DQA1*0501 (RR = 4.1, Pc = 0.001). As for protective alleles, we detected a high frequency of DRB1*13 (RR = 0.059, Pc = 0.001), DQA1*0102 (RR = 0.071, Pc = 0.009) and DQB1*06 (RR = 0.125, Pc = 0.0042). Haplotype analysis showed that the main combination observed was the conformation of DQ2 (DQA1*0501-DQB1*02) in 36 patients from group I and 30 from group III. There was no statistically significant difference between the groups I and III according to the distribution of the different alleles.

CONCLUSION

We confirmed in this study the high frequency of DQ2 haplotype in CD patients and we identified new protective alleles DRB1*13, DQA1*0102 and DQB1*06. However, HLA polymorphism seems to have no evident impact on clinical outcome of CD.

Gammadelta T cells and the lymphoid stress-surveillance response

The investigation of gammadelta T cells has identified a rapid lymphoid stress-surveillance response to microbial and nonmicrobial tissue perturbation. In addition to providing local protection, this response provides an immediate source of cytokines, chemokines, and other functions that can substantially affect downstream, adaptive immunity. Recent studies have identified striking mechanisms by which gammadelta cells meet the requirements of stress surveillance. For example, high response frequencies can reflect a unique nature of antigen engagement by the T cell receptor (TCR), developmental focusing of the repertoire by selection events, or the use of nonclonotypic receptors to initiate responses. Likewise, rapid functional deployment can be facilitated by the preprogramming of gammadelta cells during development. Additionally, gammadelta cells can directly influence adaptive immunity by functioning as antigen-presenting cells. With lymphoid stress surveillance likely to underpin numerous aspects of inflammation, tumor immunology, infectious disease, and autoimmunity, this perspective considers its properties and its emerging potential for clinical manipulation.

Genetic influence of the nonclassical major histocompatibility complex class I molecule MICB in multiple sclerosis susceptibility

It has been widely reported that the major histocompatibility complex (MHC) class II region provides the main genetic contribution to multiple sclerosis (MS) susceptibility. However, recent studies have suggested that the MHC class I region may also contribute to the development of MS. In this study, we investigated the possible association of the human leukocyte antigen (HLA)-B, MHC class I chain-related gene B (MICB) and MHC class I chain-related gene A (MICA) genes, located in the MHC class I region, with MS susceptibility. For this purpose, we analyzed the distribution of HLA-DR, HLA-B, MICB and MICA alleles in 121 MS patients and 156 healthy controls. Neither HLA-B nor MICA alleles were found to be associated with MS susceptibility, and only the frequency of HLA-DRB1*01 allele was found to be increased in controls (31% vs 14%, P(c) = 0.011). However, MICB*004 allele frequency was significantly increased in MS patients (46.3% vs 23.3%, P(c) < 0.001, odds ratio = 2.82, 95% confidence interval = 1.68-4.73). Although, MICB*004 and HLA-DRB1*15 belong to the AH 7.1 ancestral haplotype, the association of MICB*004 to MS susceptibility was found to be independent of HLA-DRB1*15 in our population. This and previous studies clearly suggest that the MHC class I, in addition to class II, could be involved in MS susceptibility.

Increased prevalence of celiac disease without gastrointestinal symptoms in adults MICA 5.1 homozygous subjects from the Campania area

OBJECTIVES

Polymorphisms in the major histocompatibility complex class I chain-related gene A may influence its binding to the Natural Killer Cell Receptor G2D (NKG2D). We looked for polymorphisms in major histocompatibility complex class I chain-related gene A exon 5 and in Human Leukocyte Antigen (HLA)-DQ/DR in adult coeliac disease patients to determine whether they affected coeliac disease phenotypes.

METHODS

Adult coeliac disease patients with (n=98) and without (n=93) gastrointestinal symptoms (gastrointestinal symptoms+/gastrointestinal symptoms-) and 108 control subjects from Campania (Italy) were characterized by Polymerase Chain Reaction (PCR) sequence specific oligonucleotide followed by PCR sequence specific primer assays for HLA DQ/DR, and by PCR followed by capillary electrophoresis for major histocompatibility complex class I chain-related gene A exon 5 polymorphisms. Immunoglobulin A (IgA) anti-transglutaminase antibodies were also evaluated by immunosorbent assay.

RESULTS

Five different major histocompatibility complex class I chain-related gene A alleles were detected in both coeliac disease patients and control subjects. The major histocompatibility complex class I chain-related gene A 5.1 allele occurred more frequently in patients than in controls (p<0.05), and the major histocompatibility complex class I chain-related gene A 5.1/5.1 homozygous genotype increased the risk of gastrointestinal symptoms- coeliac disease (OR=2.79, 95% CI 1.15-6.79). Gastrointestinal symptoms- coeliac disease patients bearing major histocompatibility complex class I chain-related gene A 5.1/5.1 alleles showed lower anti-transglutaminase levels (18U/L) than the gastrointestinal symptoms+ coeliac disease patients (35U/L). HLA-DQ2/DQ8 genotypes did not differ between gastrointestinal symptoms+ and gastrointestinal symptoms- coeliac disease, although DQ8 tended to be more frequent in gastrointestinal symptoms- coeliac disease (11.7%) than in gastrointestinal symptoms+ coeliac disease (6%).

CONCLUSIONS

Our study shows that a double dose of the major histocompatibility complex class I chain-related gene A 5.1 allele could predispose to the onset of gastrointestinal symptoms- coeliac disease. We can hypothesize that a lower level of immunological involvement in gastrointestinal symptoms- coeliac disease patients is associated with absence of gastrointestinal symptoms. This test could represent a second step in the genetic typing of high-risk subjects such as first-degree relatives of coeliac disease patients positive for the DQ2/DQ8 molecule.

Homozygosity for premature stop codon of the MHC class I chain-related gene A (MIC-A) is associated with early activation of islet autoimmunity of DR3/4-DQ2/8 high risk DAISY relatives

We hypothesized that homozygosity for the major histocompatibility complex (MHC) class I chain-related gene A (MIC-A)5.1 allele with premature stop codon would increase diabetes risk of individuals followed from infancy in the DAISY study (Diabetes Autoimmunity Study in the young). Forty five percent (10/22) of relatives (siblings and offspring cohort, SOC) who developed anti-islet autoantibodies were MIC-A5.1/5.1 homozygous. Of SOC individuals without autoantibodies, 12/58 (19%, p = 0.02) were MIC-A5.1 homozygous. By life table analysis of expression of autoantibodies, DR3-DQ2/ DR4-DQ8 more than 50% of MIC-A5.1 homozygous children became autoantibody positive by 7 years of age, compared to delayed development of autoantibodies for non-MIC-A5.1/5.1 DR3-DQ2/ DR4-DQ8 children (p = 0.005). For DR3-DQ2/DR4-DQ8 nonrelatives, the risk of activating anti-islet autoimmunity remained low even with MIC-A5.1 homozygosity suggesting that there are additional factors contributing to the marked risk of relatives compared to the general population with the DR3-DQ2/DR4-DQ8 genotype.

Genome-wide linkage analysis of 160 North American families with celiac disease

Celiac disease (CD) is a common autoimmune disease caused by exposure to the protein gliadin in wheat, and related prolamins in barley and rye. The prevalence of the disease in the US is 1:133. The aim of this study was to identify non-human leukocyte antigen (HLA) loci that predispose to CD. A genome-wide search of 405 microsatellite markers was performed on DNA samples from 160 families with a minimum of two cases of CD. Multipoint, parametric and non-parametric linkage (NPL) analyses were performed. Locations on chromosomes 1q, 3q, 6p, 6q, 7q, 9q and 10q showed linkage statistics (NPL scores or heterogeneity logarithm of the odds (HLOD) scores) of approximately 2.0 or larger. The greatest evidence for linkage outside of chromosome 6 was on 7q and 9q. An NPL score of 2.60 occurred at position 151.0 on 7q and a HLOD score of 2.47 occurred at position 144.8 on 9q under a recessive model. As expected, there was highly significant linkage to the HLA region on 6p, with NPL and HLOD scores exceeding 5.50. In conclusion, this genome-wide linkage analysis represents one of the largest such studies of CD. The most promising region is a putative locus on 7q, a region reported independently in previous genome-wide searches.

Celiac disease

Celiac disease (CD) is a common autoimmune disorder, induced by the intake of gluten proteins present in wheat, barley and rye. Contrary to common belief, this disorder is a protean systemic disease, rather than merely a pure digestive alteration. CD is closely associated with genes that code HLA-II antigens, mainly of DQ2 and DQ8 classes. Previously, it was considered to be a rare childhood disorder, but is actually considered a frequent condition, present at any age, which may have multiple complications. Tissue transglutaminase-2 (tTG), appears to be an important component of this disease, both, in its pathogenesis and diagnosis. Active CD is characterized by intestinal and/or extra-intestinal symptoms, villous atrophy and crypt hyperplasia, and strongly positive tTG auto-antibodies. The duodenal biopsy is considered to be the "gold standard" for diagnosis, but its practice has significant limitations in its interpretation, especially in adults. Occasionally, it results in a false-negative because of patchy mucosal changes and the presence of mucosal villous atrophy is often more severe in the proximal jejunum, usually not reached by endoscopic biopsies. CD is associated with increased rates of several diseases, such as iron deficiency anemia, osteoporosis, dermatitis herpetiformis, several neurologic and endocrine diseases, persistent chronic hypertransami-nasemia of unknown origin, various types of cancer and other autoimmune disorders. Treatment of CD dictates a strict, life-long gluten-free diet, which results in remission for most individuals, although its effect on some associated extraintestinal manifestations remains to be established.

Killer Ig-like receptor (KIR) genotype and HLA ligand combinations in ulcerative colitis susceptibility

Killer immunoglobulin-like receptors (KIRs) are expressed on natural killer cells and some T-cell subsets and produce either activation or inhibitory signals upon binding with the appropriate human leucocyte antigen (HLA) ligand on target cells. Recent genetic association studies have implicated KIR genotype in the development of several inflammatory conditions. Ulcerative colitis (UC) is an inflammatory disorder of the colonic mucosa that results from an inappropriate activation of the immune system driven by host bacterial flora. We developed a polymerase chain reaction-sequence specific primer (SSP)-based assay to genotype 194 UC patients and 216 control individuals for 14 KIR genes, the HLA-Cw ligand epitopes of the KIR2D receptors and a polymorphism of the lectin-like-activating receptor NKG2D. Initial analysis found the phenotype frequency of KIR2DL2 and -2DS2 to be significantly increased in the UC cohort (P=0.030 and 0.038, respectively). Logistic regression analysis revealed a protective effect conferred by KIR2DL3 in the presence of its ligand HLA-Cw group 1 (P=0.019). These results suggest that KIR genotype and HLA ligand interaction may contribute to the genetic susceptibility of UC.

Clinical behavior of multiple sclerosis is modulated by the MHC class I-chain-related gene A

It is well known that certain HLA class II alleles confer an increased risk for developing multiple sclerosis (MS). Recent studies have suggested HLA class I as a region that may also contribute to the development of MS. In this study, we investigated the association between HLA-DR, HLA-B alleles, and major histocompatibility complex (MHC) class I-chain-related gene A (MICA) transmembrane (MICA-TM) polymorphisms and disease progression in 104 MS patients and 116 healthy controls. DR1 was found to be decreased in patients when compared with controls (p(c) = 0.012). Neither HLA-B nor HLA-DR alleles were found to be associated with MS susceptibility. Furthermore, the prevalence of MICA-A5 in patients with relapsing MS was 9% while the prevalence in progressive forms was 42% (p(c) = 0.0015). The extended haplotypes related to MICA-TM5 that were found in our population were DR7-MICA5-B64 (EH 64.1, delta(s) = 0.38), DR4-MICA5-B62 (EH 62.1, delta(s) = 0.28), and DR11-MICA5-B35 (EH35.1, delta(s) = 0.10), but none of them were found to be associated to MS susceptibility or disease progression. Our data could indicate a possible role of MICA-TM in MS prognosis.

MHC class I chain-related gene B promoter polymorphisms and celiac disease

The possibility that susceptibility to celiac disease (CD) might be influenced by the MHC class I chain-related gene family, MICA and MICB, has been previously reported. In this study, we analyzed the MICB promoter and examined the association of the polymorphisms found within such in a group of CD patients. To study the MICB promoter we sequenced the 5' flanking region of MICB gene in DNA from homozygous B-lymphoblastoid cell lines corresponding to the most frequent MICB alleles found in our population (MICB*00502, MICB*002, MICB*004, and MICB*008). DNA from a MICB*003 homozygous individual was also analyzed. Sequence analysis revealed six single nucleotide polymorphisms located at positions 45860 C/A, 45862 G/C, 45877 C/G, 46113 A/C, 46219 G/C, and 46286 G/C and an insertion of 2 bp --/AG at position 45944 according to the published genomic sequence. Those polymorphisms were found to be associated in four different haplotypes corresponding to different MICB alleles. Subsequently, 126 CD subjects and 117 healthy controls were typed by polymerase chain reaction using sequence-specific primers for these polymorphisms. MICB promoter polymorphism haplotypes were also found in our population and showed strong linkage disequilibrium with MICB alleles. MICB promoter polymorphism Haplotype 3, included in MICB*002 and MICB*008 alleles, was found to be overrepresented in CD patients (79.4% CD patients vs 45.3% healthy controls; p(c) < 0.0001; OR = 4.64; CI 95% = 2.64-8.16). Both MICB*008 and MICB*002 alleles were found as part of the CD susceptibility extended haplotypes B8/DR3/DQ2, B18/DR3/DQ2, and DR4/DQ8.

HLA and eye disease: a synopsis

Human leukocyte antigen (HLA) gene products have been implicated in the pathogenesis of an increasing number of eye diseases, mainly inflammatory in nature. This perspective reviews the current hypotheses for why HLA polymorphisms are associated with specific eye diseases. Statistical problems in studies involving HLA associations are discussed, and possible solutions outlined. The relevance of HLA testing in routine ophthalmic practice, its practical and cost implications is also assessed.

Complement factor B allotypes in the susceptibility and severity of coeliac disease in patients and relatives

The alternative pathway of complement plays an important role in the pathogenesis of coeliac disease (CD), where factor B (BF) is central to its activation. CD is a gluten-sensitive enteropathy that results from a complex interplay between genetic, immunologic, and environmental factors. In this study we evaluated the association of BF allotypes with the susceptibility and severity of CD, and with the presence of autoantibodies. Seventy-six non-related patients (56 female; 20 male; 2-77 years) and 150 first-degree relatives (87 female, 63 male; 2-75 years) were investigated. As controls, 97 healthy individuals were included (67 female;, 30 male; 1-71 years). The BF allotypes were determined by high-voltage agarose gel electrophoresis, followed by specific immunofixation. Disease severity was evaluated by anti-endomisial antibody (IgA-EmA) titres and histological findings of intestinal mucosa, which showed a high correlation (r = 0.8; P < 0.00001) in samples collected simultaneously. IgA-EmA was detected in all CD patients ingesting gluten, and in 13.3% of the relatives. The IgA-EmA, smooth muscle, mitochondrial, liver-kidney microsomal, nuclear, gastric parietal cells, and thyroid microsome antibodies were tested by indirect immunofluorescence. A significant decrease in BF S (P = 0.026) and an increasing tendency in BF SF allotype (P = 0.06) were observed in CD patients when compared to their relatives. On the other hand, BF S frequency was increased (P = 0.001 RR = 2.32) and BF SF (P = 0.002) decreased in the relatives when compared to the controls. No differences were observed in the distribution of BF phenotypes amongst the CD patients and the control group, and no association was found with CD severity or with the presence of autoantibodies. These results suggest BF SF as a CD susceptibility marker, and BF S as a protection marker of the disease amongst CD families in the Brazilian population.

Association of MHC class I chain related gene-A microsatellite polymorphism with the susceptibility to T1DM and LADA in Czech adult patients

The results in this study suggest that microsatellite polymorphism within the transmembrane region of MIC-A gene is associated with genetic susceptibility to adult-onset of type 1 diabetes mellitus (T1DM), MIC-A5.1 allele, corrected P = 0.001, whereas it is not associated with latent autoimmune diabetes in adults (LADA) in Czech population. According to our findings, we can hypothesize that adult-onset T1DM and LADA may have partly different immunogenetic aetiopathogenesis.

MICA Polymorphism in a Population From North Morocco, Metalsa Berbers, Using Sequence-Based Typing

The MICA gene encodes a family of nonclassical major histocompatibility complex class I molecules. Data on MICA polymorphism in different populations are still limited. In the present study, MICA allele frequencies (af) were assessed in 82 unrelated healthy individuals from a Moroccan Berber population named Metalsa (ME) by means of sequence-based typing of exons 2, 3, 4, and 5. In consideration of the linkage disequilibrium existing between MICA and human leukocyte antigen (HLA) class I alleles, MICA/HLA-B, MICA/HLA-Cw, and MICA/HLA-A haplotype frequencies (hf) were estimated. A wide allelic distribution including 16 different MICA alleles was found in ME. The most common MICA alleles were MICA*00801 (af = 0.268), *004 (0.232), *00902 (0.140), *00901 (0.085), and *00901 (0.073). The most common MICA/HLA-B haplotypes were MICA*004-B*4403 and MICA*009-B*50 (hf = 0.113 for both these haplotypes). Some known MICA and HLA-B associations were confirmed in this population. Noteworthy was the high frequency of MICA*009 (af = 0.226); the high frequency of B*50 found in ME (af = 0.114) permitted us to evidence the associations of MICA*00902 with B*5001 (hf = 0.068) or *5002 (hf = 0.045), whereas MICA*00901 was mainly associated with B*5101 (hf = 0.038), which corresponds to the previously described association MICA*009/A6-HLA-B*51. This study extends the previous knowledge on MICA polymorphism to a North African white population and may have implications for disease associations and transplantation.

Genetic testing: who should do the testing and what is the role of genetic testing in the setting of celiac disease?

Celiac disease is a remarkable and common immune-mediated disorder determined by both the presence of characteristic HLA alleles (DQ2 and DQ8) and one of the best characterized environmental factors (gliadin) for any common autoimmune disease. The discovery of transglutaminase autoantibodies and the development of assays for these antibodies has allowed the identification of a large number of asymptomatic individuals with autoimmunity and intestinal biopsy evidence of celiac lesions. Further understanding of the sequelae of asymptomatic celiac disease, and the interaction between genetic susceptibility and environmental factors, are likely to alter fundamentally both genetic screening for celiac disease and its therapy.

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.

[Genetics and immunopathogenics aspects of the celiac disease: a recent vision]

BACKGROUND

Celiac disease, or gluten-sensitive enteropathy, is a strongly inherited condition. Although the genetic association of CD with the DQ2 and DQ8 HLA haplotypes has been known for long, others HLA and non-HLA genes are also important in the development of the disease. Celiac disease results of the combined effect of different normally functioning genes' products. The tissue damage in celiac disease is immunologically mediated and several effector mechanisms are responsible for the disease expression. The interplay between genetic, immunological and environmental factors explains the large spectrum of clinical, histological and serological alterations observed in the different stages of the disease development, pointing out to the polygenic nature of celiac disease.

CONCLUSION

The recent advances in the understanding of the immunopathogenesis, genetics and diagnoses of celiac disease have allowed the revision of strict concepts and previous criteria and their adequation to the new evidences, aiming a better diagnostic and orientation to celiac patients and relatives.

MICA response to gliadin in intestinal mucosa from celiac patients

MHC class I chain-related gene A (MICA), a putative independent susceptibility gene in autoimmune diseases, encodes a surface protein present in epithelial cells that binds to NKG2D, an activating receptor of NK, alphabeta and gammadelta T cells, and could function as a stress-inducible activator of the innate immune response. There is no evidence of a long-term implication of MICA in the celiac autoimmune process. However, it could be that gliadin activation of MICA occurs only during the initial stages of the disease. In order to determine whether MICA is activated in response to gliadin in patients with celiac disease (CD), small intestinal mucosa biopsy samples from ten long-standing celiac patients on a gluten-free diet and from five non-celiac individuals were incubated with and without gliadin for 4 h. Total RNA was purified and MICA, IFNG and NKG2D mRNA were quantified by fluorescent real-time RT-PCR. Expression levels were calculated relative to GAPDH. MICA expression was detected in both patients and controls, but incubation with gliadin induced a strong increase in samples from the treated CD group compared with the non-CD controls (P=0.028), while no differences were observed for IFNG or NKG2D mRNA levels. The gliadin-provoked over-expression of MICA in "normalized" tissues from CD patients suggests a role for this stress-induced activator of the immune response in the early stages of organ-specific autoimmune destruction, probably preceding the onset of inflammation.

A Direct Role for NKG2D/MICA Interaction in Villous Atrophy during Celiac Disease

MICA molecules interact with the NKG2D-activating receptor on human NK and CD8 T cells. We investigated the participation of the MICA/NKG2D pathway in the destruction of intestinal epithelium by intraepithelial T lymphocytes (IEL) in Celiac disease and its premalignant complication, refractory sprue. We show that MICA is strongly expressed at epithelial cell surface in patients with active disease and is induced by gliadin or its p31-49 derived peptide upon in vitro challenge, an effect relayed by IL-15. This triggers direct activation and costimulation of IEL through engagement of NKG2D, leading to an innate-like cytotoxicity toward epithelial targets and enhanced TCR-dependent CD8 T cell-mediated adaptive response. Villous atrophy in Celiac disease might thus be ascribed to an IEL-mediated damage to enterocytes involving NKG2D/MICA interaction after gliadin-induced expression of MICA on gut epithelium. This supports a key role for MIC/NKG2D in the activation of intraepithelial immunity in response to danger.

Human MHC class I chain related (MIC) genes: their biological function and relevance to disease and transplantation

Major histocompatibility complex (MHC) class I chain related (MIC) molecules show homology with classical human leukocyte antigen (HLA) molecules, but they do not combine with beta2 microglobulin, do not bind peptide and are not expressed on normal circulating lymphocytes. In response to stress, MIC proteins are expressed on the cell surface of freshly isolated gastric epithelium, endothelial cells and fibroblasts and engage the activating natural killer cell receptor NKG2D, which is found on many cells within the immune system. Despite the highly polymorphic nature of MIC genes, only one polymorphic position has been identified that appears to affect the binding of NKG2D. Alleles with a methionine at codon 129 have a 10-50-fold greater capacity to complex NKG2D than alleles with a valine at this position. Renal and pancreatic grafts with evidence of both acute and chronic rejection have been shown to express MIC proteins, and anti-MIC antibodies have been identified in the serum of these patients. Some MIC molecules which are expressed by tumours appear to shed and solubilize in plasma. This soluble form of MIC engages cells expressing NKG2D, rendering them inactive, and impairs tumour cytolysis. Similarly, a protein encoded by human cytomegalovirus (CMV) prevents MICB surface expression and subsequent NKG2D interaction. Whereas the benefit of solid organ transplantation may be hindered by the expression of MIC molecules on grafts, tumours and viruses may take advantage of the expression of MIC molecules on transformed and virus-infected cells in order to evade this recognition pathway.

MHC class I region plays a role in the development of diverse clinical forms of celiac disease in a Saharawi population

OBJECTIVE

The aim of this study was to investigate the association of MHC genes in the development of celiac disease (CD) and its diverse clinical forms in a Saharawi population.

METHODS

One hundred and twenty-five CD patients and 98 healthy controls were selected from the Saharawi refugee camps in Tindouf. All were investigated for the presence of antitransglutaminase 2 antibodies. Patients were divided into two groups according to their clinical manifestations: 70 typical and 55 atypical. Patients and controls were typed for HLA-B, DRB1, DQB1, and DQA1, and for MICA transmembrane polymorphism.

RESULTS

The frequency of HLA-DQ2 in Saharawi controls was notably increased compared with other populations. No differences in the distribution of DQ2 in either group of patients were found. However, the haplotype B8/DR3/DQ2 was notably overrepresented in atypical patients compared to typical ones (pc= 0.001). The MICA-A5.1 allele was increased in atypical CD patients compared to those with typical forms (pc= 0.0006). Finally, we found that the increased frequency of MICA-A5.1 in the atypical group was independent of the linkage disequilibrium with B8/DR3/DQ2 haplotype (p= 0.02).

CONCLUSIONS

The elevated prevalence of CD in Saharawi seems to be related to the high frequency of HLA-DQ2 in this population. However, the development of atypical or typical forms of the disease may be due to a gene or genes located in the class I side of the haplotype B8/DR3/DQ2, especially MICA. This appears not to be implicated in the susceptibility to CD but may play an important role in the development of the different forms of the disease.

Association of MHC class I related gene B (MICB) to celiac disease

BACKGROUND AND AIMS

Celiac disease (CD) is an enteropathic disorder characterized by strong association with HLA-DQ2. Our aim was to investigate whether MICB, a gene located in the MHC class I region, may contribute to CD susceptibility.

PATIENTS AND METHODS

Total of 133 CD patients, previously reported to be associated with MICA-A5.1, and 116 controls were initially analyzed. Twenty-eight additional DQ2-negative CD patients were also studied. MICB was typed by PCR using sequence-specific primers. HLA-B, -DRB1, -DQA1, -DQB1, and MICA were also typed.

RESULTS

The allele MICB0106 was strongly associated with CD (pc < 0.000001, odds ratio (OR) = 5.6, 95% confidence interval (CI) = 3.1-10.1) and it was overrepresented in atypical patients compared with typical ones (pc = 0.04, OR = 2.9, CI = 1.4-6.1). MICB0106 was part of DR3-DQ2 haplotype (B8-MICA-A5.1-MICB0106-DR3-DQ2), and consequently a strong linkage disequilibrium between MICB0106 with DQ2 (lambdas = 1) and MICA-A5.1 (lambdas = 0.55) was found. To analyze whether the association of MICB is independent of this haplotype, its association was also studied in DQ2-negative patients (n = 46). DQ8 (28%vs 9%, p = 0.0085, pc = NS) and MICB0104 (52%vs 30%, p = 0.01, pc = NS) were increased in DQ2-negative patients. MICA-A5.1 was significantly increased in atypical patients (p(c)= 0.001, OR = 6.4, CI = 2.2-18.4), and this association was independent of DQ2 and DQ8 (pc = 0.02, OR = 2.6, CI = 1.1-6.1).

CONCLUSIONS

The expression of MIC genes on enterocytes under stressful conditions and their function as ligands of intraepithelial gammadelta and CD8 T cells, together with the data presented here suggest a potential role of MIC genes in the pathogenesis of CD.

Defining the contribution of the HLA region to cis DQ2-positive coeliac disease patients

The major genetic susceptibility to coeliac disease is contributed by the human leukocyte antigen (HLA) region. The primary association is with the HLA-DQ2 molecule, encoded by the DQA1*05 and DQB1*02 alleles, which is expressed by over 90% of patients. The aim of our study was to perform an extensive scan of the entire HLA region to determine whether there is evidence for the presence of additional HLA susceptibility genes for coeliac disease in the Dutch population, acting independently of DQ2. In all, 16 microsatellite markers and the DQA1 and DQB1 genes were genotyped in simplex cis DQ2-positive coeliac disease families and cis DQ2-positive control families. Allele frequencies of markers on phase-known DQ2-positive haplotypes transmitted to patients were compared to a combined group of DQ2-positive nontransmitted and control haplotypes, thereby controlling for the DQ2 contribution. No significant differences at any of the marker loci were detected, suggesting that DQ2 is the major HLA risk factor for coeliac disease. Individuals homozygous for DQ2 or heterozygous for DQA1*05-DQB1*02/DQA1*0201-DQB1*02 were found to be at five-fold increased risk for development of coeliac disease (P<10(-8)). This risk seems to be conferred by the presence of a second DQB1*02 allele next to one DQA1*05-DQB1*02 haplotype, independently of the second DQA1 allele.

Familial occurrence of inflammatory bowel disease in celiac disease

BACKGROUND

The authors have previously reported a possible increased risk of the familial occurrence of Crohn's disease in patients with celiac disease.

AIM

The aim of the current study was to evaluate in a case-control study the familial occurrence of inflammatory bowel disease (IBD) in first-degree relatives of patients with celiac disease.

METHODS

One hundred eleven consecutive patients with biopsy-proven celiac disease were interviewed to ascertain whether IBD was present in first-degree relatives. The number of relatives, their ages, and possible IBD status were collected in a questionnaire. When a diagnosis of familial IBD was reported, the diagnosis was checked in the hospital records. Two hundred twenty-two controls matched for age and sex (111 from the general population and 111 from orthopedic wards) were also interviewed regarding the possible occurrence of IBD in first-degree relatives. The chi2 test was used to evaluate the difference in proportion of familial occurrence of IBD among individuals with celiac disease and controls.

RESULTS

Among 600 first-degree relatives of patients with celiac disease, 10 cases of IBD were identified among first-degree relatives (7 cases of ulcerative colitis and 3 cases of Crohn's disease), whereas only 1 case of IBD was identified among the 1,196 first-degree relatives of control patients (p < 0.01). When ulcerative colitis and Crohn's disease were analyzed separately, only the prevalence of ulcerative colitis was statistically significant (p </= 0.02).

CONCLUSIONS

This case-control study shows that there is a significantly increased prevalence of familial ulcerative colitis in patients with celiac disease. There was no significant increase in the prevalence of Crohn's disease in patients with celiac disease. The possible role of this association is discussed.