Analysis of microsatellite polymorphism around the HLA-B locus in Iranian patients with Behçet's disease

Diversity of HLA class I and class II alleles in Iran populations: Systematic review and Meta-Analaysis

The human leukocyte antigen (HLA) system plays an essential role in the peptides antigen presentation and more regulation of immune responses. Regarding all HLA molecules' associations with various diseases and their clinical utilities in understanding drug reactions or prediction of transplantation outcome, there is a need for much more extensive HLA data generated from Asian countries.

METHOD

A comprehensive search was conducted in electronic databases between 1990 and 2021 to identify relevant articles to HLA frequency in the normal Iranian population. Two independent reviewers screened and selected the eligible studies. After data extraction, the meta-analysis was performed using STATA version 14. The overall frequencies and their 95% confidence intervals (CIs) were obtained using the random-effects model.

RESULTS

Among 1141 studies 78 were eligible for this study and the sample sizes varied from 14 to 15,600. The most frequent alleles of HLA class I were HLA-A*02 (22%; 95%CI: 20-24%; I² = 88.63%), -B*35 (18%; 95%CI: 16-21%; I² = 90.95%), -C*12 (18%; 95%CI: 13-22%; I² = 89.51%). HLA-DQA1*01 (42%; 95%CI: 40-44%; I² = 56.80%), -DQB1*03 (38%; 95%CI: 35-42%; I² = 92.38%), and -DRB1*11 (24%; 95%CI: 22-26%; I² = 90.72%) were the most frequent alleles of HLA class II in Iran.

DISCUSSION

Our meta-analysis results point out that the comprehensive report of HLA allele frequency in the Iranian population could be helpful as reference data for planning and managing transplantation and immune disease treatment in Iran.

Indonesians Human Leukocyte Antigen (HLA) Distributions and Correlations with Global Diseases

In Human, Major Histocompatibility Complex known as Human Leukocyte Antigen (HLA). The HLA grouped into three subclasses regions: the class I region, the class II region, and the class III region. There are thousands of polymorphic HLAs, many of them are proven to have correlations with diseases. Indonesia consists of diverse ethnicity people and populations. It carries a unique genetic diversity between one and another geographical positions. This paper aims to extract Indonesians HLA allele data, mapping the data, and correlating them with global diseases. From the study, it is found that global diseases, like Crohn's disease, rheumatoid arthritis, Graves' disease, gelatin allergy, T1D, HIV, systemic lupus erythematosus, juvenile chronic arthritis, and Mycobacterial disease (tuberculosis and leprosy) suspected associated with the Indonesian HLA profiles.

MICA*049, not MICA*009, is associated with Behçet's disease in a Chinese population

Behçet’s disease (BD) is a multi-systemic inflammatory disease. Previous reports indicated that MICA*009 confers susceptibility to BD. MICA*049 differs from MICA*009:01, a major MICA*009 subtype, only at codon 335 in exon 6. However, the potential association of MICA*049 with BD  has not been addressed. In this study, we differentiated association among MICA*049, MICA*009 and HLA-B*51 with BD. A Han Chinese cohort consisting of 41 BD patients and 197 ethnically matched controls were examined with sequencing and T-ARMS-PCR for genotyping of MICA, and ARMS-PCR for HLA-B*51. The phenotype frequency of MICA*049 (41.5% versus 8.1%, OR = 8.01, P = 1.91 × 10⁻⁸) and HLA-B*51 (46.3% versus 15.7%, OR = 4.62, P = 1.21 × 10⁻⁵) were significantly higher in BD patients than those in controls, whereas MICA*009 showed no significant difference between the two groups (17.1% versus 13.2%, OR = 1.35, P = 0.51). After stratification for the effect of HLA-B*51, MICA*049 was still associated with BD in HLA-B*51 negative patients (OR = 40.61, P = 0.02). Our results indicate that MICA*049, not MICA*009, is a risk factor to BD, and that is independent from HLA-B*51 in the Han Chinese cohort.

Comprehensive analysis of the association between UBAC2 polymorphisms and Behçet's disease in a Japanese population

Behçet’s disease (BD) is reportedly associated with polymorphisms of the ubiquitin-associated domain containing 2 (UBAC2) gene in Turkish, Italian, and Chinese populations. Here we investigated whether UBAC2 polymorphisms were associated with BD in a Japanese population. Using data from 611 Japanese BD patients and 737 Japanese controls who participated in our previous genome-wide association study, we analyzed the 58 genotyped single-nucleotide polymorphisms (SNPs) in the region 100 kb upstream and downstream of UBAC2. We also performed imputation analysis in the region, with 562 imputed SNPs included in the statistical analyses. Association testing revealed that the T allele of rs9517723 in the lncRNA LOC107984558 was significantly associated with ocular and central nervous system (CNS) lesions and showed the strongest association under the recessive model (TT vs. CT+CC: ocular lesion, Pc = 0.0099, OR = 1.56; CNS lesion, Pc = 0.0052, OR = 3.42). Expression analysis revealed that rs9517723 TT homozygotes showed significantly increased UBAC2 expression (P < 0.05). Our findings suggest that enhanced UBAC2 expression associated with the homozygous risk allele (TT) of rs9517723 could induce overactivation of ubiquitination-related pathway, resulting in the development of ocular and CNS lesions in BD.

Associations between major histocompatibility complex class I chain-related gene A polymorphisms and susceptibility to Behcet's disease. A meta-analysis

OBJECTIVE

The purpose of this work was to investigate whether major histocompatibility complex class I chain-related gene A (MICA) polymorphisms are associated with susceptibility to Behcet's disease (BD).

METHODS

A meta-analysis was conducted on the associations between the MICA-transmembrane (TM) A6 allele and the 009 allele of MICA exon 2-4 (MICA*009) and BD with or without HLA-B51 overall and in each ethnic group.

RESULTS

Fifteen comparison studies were included in this meta-analysis. The meta-analysis revealed a significant association between the MICA-TM A6 allele and BD in European, Asian, and Arab populations [odds ratio (OR) 1.436, 95 % confidence interval (CI) 1.111-1.857, p = 0.006; OR 1.999, 95 % CI 1.551-2.575, p = 8.0 × 10(-8); OR 1.333, 95 % CI 1.058-2.300, p = 0.025, respectively,]). Stratification by HLA-B51 showed an association between the MICA-TM A6 allele and BD with HLA-B51 in the overall group and in the European population. Meta-analysis showed a significant association between the MICA*009 allele and BD in the overall group (OR 3.948, 95 % CI 2.680-5.815, p < 1.0 × 10(-8)) and in the European population (OR 3.392, 95 % CI 2.118-5.433, p = 5.6 × 10(-6)). A significant association was found between the MICA*009 allele and B51-positive BD.

CONCLUSION

This meta-analysis shows that the MICA-TM A6 allele and the MICA*009 allele are associated with BD susceptibility in various ethnic populations, and that MICA alleles are in strong linkage disequilibrium with HLA-B51 in BD.

A meta-analysis of the association between Behçet's disease and MICA-A6

Behçet's disease (BD) is a multi-system inflammatory condition with unknown cause, characterized by a triple-symptom complex of recurrent oral aphthous ulcers, genital ulcers, and uveitis and skin lesions. It predominantly affects people living around the Mediterranean basin and in Japan. The effects of the major histocompatibility complex class I chain related gene A (MICA) A6 allele on susceptibility to Behçet's disease (BD) have been reported previously, however, their results have been unreliable. The present study aimed to determine whether an association between the MICA-A6 allele and BD susceptibility exists. A total of 12 case-control studies, examining the association between MICA-A6 and BD and involving 752 cases and 1,175 controls were included in the present meta-analysis. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. The results of meta-analysis revealed that the frequency of the MICA-A6 allele in the case group was significantly higher than those in the control groups (P<0.001, OR=2.43, 95% CI: 1.99-2.97). Sub-group analysis by ethnicity indicated that the association between of MICA-A6 gene to BD remained in Asian populations (5 cases and 731 controls) and Caucasian populations (242 cases and 444 controls) with OR=2.65, 95% CI: 2.07-3.38 and OR=2.23, 95% CI: 1.37-3.62, respectively. These findings demonstrate that MICA-A6 gene is associated with susceptibility to BD. The MICA-A6 gene may serve as an early diagnostic marker for BD in the future.

Association between Functional MICA-TM and Behcet's Disease: A Systematic Review and Meta-analysis

The relationships between polymorphisms of the trans-membrane(TM) region located in the major histocompatibility complex (MHC) class I chain-related gene A (MICA) and Behcet's disease (BD) have been discussed previously, however, the results were contradictory. In this study, we thoroughly assess whether MICA-TM gene variants are associated with BD by means of a systematic review and meta-analysis. Our study focused on the effects of polymorphisms of MICA-A4, A5, A5.1, A6, and A9 from the included articles. Sixteen previous original publications representing 1,555 BD patients and 2,086 unrelated healthy controls analyzed the association of BD with MICA-TM gene polymorphisms. For the five alleles, MICA-A6 showed a strongly positive correlation with BD patients and could be viewed as an increased risk factor of BD (OR = 2.34, 95%CI: 2.02-2.70). Furthermore, MICA-A4, A5, A5.1, and A9 exhibited negative associations with BD (OR = 0.71, 95%CI: 0.58-0.86; OR = 0.75, 95%CI: 0.63-0.90; OR = 0.63, 95%CI: 0.44-0.91; OR = 0.70, 95%CI: 0.58-0.84, respectively). Our meta-analysis confirmed MICA-A6 could be responsible for BD in three ethnic regions and should probably be treated as a risk factor for BD. MICA-A4, A5, A5.1, and A9 could be regarded as protective factors, especially in the Middle East and East Asia.

Associations of MICA Polymorphisms with Inflammatory Rheumatic Diseases

Inflammatory rheumatic diseases are characterized by inflammation resulting from the immune dysregulation that usually attacks joints, skin and internal organs. Many of them are considered as complex disease that may be predisposed by multiple genes and/or genetic loci, and triggered by environmental factors such as microbiome and cellular stress. The major histocompatibility complex class I chain-related gene A (MICA) is a highly polymorphic gene that encodes protein variants expressed under cellular stress conditions, and these MICA variants play important roles in immune activation and surveillance. Recently, accumulating evidences from both genetic and functional studies have suggested that MICA polymorphisms may be associated with various rheumatic diseases, and the expression of MICA variants may attribute to the altered immune responses in the diseases. The objective of this review is to discuss potential genetic associations and pathological relevance of MICA in inflammatory rheumatic diseases that may help us to understand pathogenesis contributing to the development of these diseases.

Identification of a susceptibility locus in STAT4 for Behçet's disease in Han Chinese in a genome-wide association study

OBJECTIVE

To identify susceptibility loci for Behçet's disease (BD) and elucidate their functional role.

METHODS

A genome-wide association study (GWAS) and functional studies were conducted. A total of 149 patients and 951 controls were enrolled in the initial GWAS, and 554 patients and 1,159 controls were enrolled in the replication study. Real-time polymerase chain reaction, luciferase reporter assay, and enzyme-linked immunosorbent assay were performed.

RESULTS

Our GWAS and replication studies identified a susceptibility locus around STAT4 (single-nucleotide polymorphisms [SNPs] rs7574070, rs7572482, and rs897200; P = 3.36 × 10(-7) to 6.20 × 10(-9) ). Increased expression of STAT4 was observed in individuals carrying the rs897200 risk genotype AA. Consistent with the idea that STAT4 regulates the production of interleukin-17 (IL-17) and interferon-γ, IL17 messenger RNA and protein levels were increased in individuals carrying the rs897200 risk genotype AA. Interestingly, the risk allele A of rs897200 creates a putative transcription factor binding site. To test whether it directly affects STAT4 transcription, an in vitro luciferase reporter gene assay was performed. Higher transcription activity was observed in individuals carrying the risk allele A, suggesting that rs897200 is likely to directly affect STAT4 expression. Additionally, 2 SNPs, rs7574070 and rs7572482, which are tightly linked with rs897200, were cis-expression quantitative trait loci (eQTL) SNPs, suggesting that SNP rs897200 is an eQTL SNP. Most importantly, the clinical disease severity score was higher in individuals with the rs897200 risk genotype AA.

CONCLUSION

These findings strongly suggest that STAT4 is a novel locus underlying BD. We propose a model in which up-regulation of STAT4 expression and subsequent STAT4-driven production of inflammatory cytokines, such as IL-17, constitute a potential pathway leading to BD.

New insights into the pathogenesis of Behçet's disease

Behçet's disease (BD) is a recurrent systemic inflammatory disorder of unknown origin characterized by oral and genital mucous ulcer, uveitis, and skin lesions. Involvement of large vessels, central nervous system (CNS), gastrointestinal tract and thrombotic events are less frequent but can be life threatening. The aim of this review is to provide new insights into the pathogenesis of BD. Over the past year substantial advances have been done in the understanding of the genetic [1,2] and immunology [3] of BD. BD is at the crossroad between autoimmune and autoinflammatory syndromes. In common with autoimmune diseases BD shares class I MHC association. However, in contrast to autoimmune disorders, BD has clinical features that seem to be mostly autoinflammatory. The pathogenesis of BD is still unknown, but major determinants of the genetic and immune system abnormalities have been reported recently. Triggering infectious factors are supposed to participate in the outbreak of BD in genetically predisposed patients. Two recent large genome-wide association study (GWAS) conducted in Turkey and Japan reported association between single nucleotide polymorphism (SNP) of interleukin (IL)-10 and IL-23R/IL-12RB2 genes and BD. New insights into the perturbations of T cell homeostasis of BD recently emerged. We have recently demonstrated the promotion of Th17 responses and the suppression of regulatory T cells (Tregs) that were driven by interleukin (IL)-21 production and that correlates with BD activity. Inflammatory cells within BD inflammatory lesions included mostly neutrophils, Th1 and Th17 cells, and cytotoxic CD8+ and γδ T cells. Altogether, the recent progresses in the knowledge of BD pathogenesis pave the way for innovative therapy.

Lack of an association of PD-1 and its ligand genes with Behcet's disease in a Chinese Han population

BACKGROUND

Behcet's disease is a chronic, multi-systemic autoimmune disease. Programmed cell death 1 (PD-1) gene is one of non-human leucocyte antigen genes. It has been demonstrated to be associated with several autoimmune diseases. However, only a few studies have addressed the association of ligand genes of PD-1, PD-L1 and PD-L2 with autoimmune disease. The purpose of this study was to analyze the potential association of the PD-1 and its ligand genes with Behcet's disease in a Chinese Han population.

METHODOLOGY/PRINCIPAL FINDINGS

Four single-nucleotide polymorphism (SNPs) rs2227981 and rs10204525 of PD-1, rs1970000 of PD-L1 and rs7854303 of PD-L2 were genotyped in 405 Behcet's patients and 414 age-, sex-, ethnic-matched healthy controls using polymerase chain reaction-restriction fragment length polymorphism assay. The results revealed that there were no significant differences in the genotype and allele frequencies of PD-1 rs2227981 and rs10204525 between the Behcet's patients and controls. A similar result was found for PD-L1 rs1970000 versus healthy controls. Only the C allele and the CC genotype of PD-L2 rs7854303 were identified in patients and controls. Stratification analysis based on gender and clinical findings did not show any associations between PD-1 or its ligand polymorphisms and Behcet's disease.

CONCLUSIONS/SIGNIFICANCE

None of the currently studied SNPs, PD-1 rs2227981 and rs10204525, PD-L1 rs1970000 and PD-L2 rs7854303, are associated with the susceptibility to Behcet's disease in a Chinese Han population. More studies are needed to confirm these findings in Behcet's patients with other ethnic backgrounds.

Genetic susceptibility to Behcet's disease: role of genes belonging to the MHC region

OBJECTIVE

To review the progress in the field of MHC-related genetic susceptibility to Behçet's disease (BD).

METHOD

Systematic review of the English literature between 1 January 1980 and 31 January 2010 using Medline. Case-control, population-based, observational cohort studies investigating the association between BD and HLA-B*51 subtypes, classical and non-classical HLA alleles and other HLA-related genes were selected. The geographical distribution of BD and these susceptibility genes was also taken into consideration. Case and familial case reports were excluded except for case series with more than two patients.

RESULTS

Ninety articles plus 17 obtained from other sources were included in the systematic review. We have found high evidence that a core component of genetic susceptibility to BD is within the MHC region being primarily related to an HLA-B*51 subtype: HLA-B*5101/B*510101. Moreover, HLA-A*26, HLA-B*15, HLA-B*5701 and TNF-α -1031C were independently associated with BD. Data suggest that other HLA (HLA-C, HLA-DR) and HLA-related [MHC Class I chain-related gene A (MIC-A), TNF-α] genes may play a role in BD co-susceptibility or pathogenesis. Finally, the distinctive geographical distribution of BD suggested an evolutionary selection of HLA-B*51 subtypes as the major susceptibility factors for BD.

CONCLUSION

Further studies must be addressed to clarify the functional relevance of the different genes found to be associated with disease susceptibility and the potential interactions between genes located within and outside the MHC region.

Etiopathogenesis of Behçet's disease with emphasis on the role of immunological aberrations

Behçet's disease (BD) is a chronic multisystemic inflammatory disorder of unknown origin consisting of oral aphthous ulcers, ocular symptoms, skin lesions, and genital ulcerations. It has many features in common with systemic vasculitides and is more prevalent in countries along the ancient Silk route. Immune-mediated mechanisms play a major role in the pathogenesis of the disease, and inflammatory mediators are also involved. BD is not considered to be an autoimmune disorder, and the character of the disease needs to be clarified. Immunological aberrations in BD have been extensively studied by many investigators; genetic factors have been related to disease susceptibility, but their exact role in the development of disease is uncertain. Environmental factors such as infectious agents have also been implicated in the etiology of BD. However, the etiopathogenesis of the disease remains to be elucidated. Factors involved in the immunopathogenesis of BD with emphasis on the role of immunological aberrations are analyzed in this review.

Genetics of Behçet disease inside and outside the MHC

BACKGROUND

Behçet disease (BD) is a rare, chronic, systemic, inflammatory disorder characterised by recurrent ocular, genital and skin lesions. Although its aetiology is still uncertain, an intricate interplay between the environment (eg, viruses) and the host seems to initiate and/or perpetuate the disease, although the mechanism remains speculative. Since the identification of HLA-B*5101 (and more recently of MICA) as a susceptibility locus for BD, the identification of additional genetic locus/loci, whether inside, or perhaps more importantly outside the MHC has clearly stalled.

OBJECTIVE

To carry out a genome-wide association study (GWAS) of BD.

METHODS

300 Japanese patients with BD and an equal number of controls were recruited. The samples were screened using a dense panel of 23 465 microsatellites (MS) covering the entire genome.

RESULTS

The six best (of a total of 147) positively associated MS with BD were identified. Of these six, two were located within the human leucocyte antigen (HLA) class I region itself. Although one of these was clearly reminiscent of the association with HLA-B, the second, not in linkage disequilibrium with the former, was in the telomeric side of the class I region and remained to be formally identified. HLA genotyping and haplotype analysis conclusively led to the deciphering of a dual, independent, contribution of two HLA alleles to the pathogenesis of BD: HLA-B*5101 and HLA-A*26.

CONCLUSIONS

This GWAS highlights the premier genetic susceptibility locus for BD as the major histocompatibility complex itself, wherein reside two independent loci: HLA-B and HLA-A.

Investigation of the association between Toll-like receptor 2 gene polymorphisms and Behçet's disease in Japanese patients

Behçet's disease (BD) is a chronic systemic inflammatory disorder characterized by recurrent ocular symptoms, oral and genital ulcers, and skin lesions. The etiology of BD is still uncertain, but genetic and environmental factors likely both play an important role in BD development. In the present study, we investigated whether polymorphisms of Toll-like receptor 2 (TLR2), previously reported to recognize BD candidate antigens, are associated with BD. Two hundred Japanese patients with BD and 128 Japanese healthy controls were recruited. We genotyped five single-nucleotide polymorphisms (SNPs) in the TLR2 gene and assessed the allele/genotype diversity between cases and controls for all SNPs. No significant differences in the frequency of TLR2 alleles, genotypes, and haplotypes in the BD cases were detected compared with the controls. These data indicate that TLR2 polymorphisms do not play an important role in the development of BD.

Common genetic determinants of uveitis shared with other autoimmune disorders

Uveitis is a complex multifactorial autoimmune disease of the eye characterized by inflammation of the uvea and retina, degeneration of the retina, and blindness in genetically predisposed patients. Using the rat model of experimental autoimmune uveitis (EAU), we previously identified three quantitative trait loci (QTL) associated with EAU on rat chromosomes 4, 12, and 10 (Eau1, Eau2, and Eau3). The primary goal of the current study is to delineate additional non-MHC chromosomal regions that control susceptibility to EAU, and to identify any QTLs that overlap with the QTLs of other autoimmune diseases. Using a set of informative microsatellite markers and F(2) generations of resistant and susceptible MHC class II-matched rat strains (F344 and LEW), we have identified several new significant or suggestive QTLs on rat chromosomes 2, 3, 7, 10, and 19 that control susceptibility to EAU. A protective allele was identified in the susceptible LEW strain in the Eau5 locus at D7Wox18, and epistatic interactions between QTLs were found to influence the severity of disease. The newly identified regions (Eau4 through Eau9) colocalize with the genetic determinants of other autoimmune disease models, and to disease-regulating syntenic regions identified in autoimmune patients on human chromosomes 4q21-31, 5q31-33, 16q22-24, 17p11-q12, 20q11-13, and 22q12-13. Our results suggest that uveitis shares some of the pathogenic mechanisms associated with other autoimmune diseases, and lends support to the "common gene, common pathway" hypothesis for autoimmune disorders.

Association of Major Histocompatibility Complex Class I Chain-Related Gene A and HLA-B Alleles with Behçet's Disease in Turkey

PURPOSE

Behçet's disease (BD) is known to be associated with HLA-B*51 in many different ethnic groups. Recently, the major histocompatibility complex class I chain-related gene A (MICA), located near the HLA-B gene, has been proposed as a candidate gene for BD susceptibility in several ethnic groups. To compare the relative contribution of MICA polymorphisms and HLA-B*51 to BD in different ethnic groups, we studied MICA polymorphisms in Turkish BD patients.

METHODS

Thirty-three Turkish BD patients and 65 healthy controls were enrolled for analysis of polymorphisms in the extracellular domains of MICA.

RESULTS

The phenotype frequencies of MICA*009 were significantly higher in BD patients (75.8%) than in controls (29.2%) (P = 0.000015). HLA-B*51 was also significantly more frequent in BD patients (81.8%) than in controls (29.2%) (P = 0.0000007). A strong association existed between MICA*009 and HLA-B*51. To assess the confounding effect of MICA*009 on HLA-B*51, we performed a stratification analysis that showed that BD was distinctly associated only with HLA-B*51.

CONCLUSION

Our results indicate that the major susceptibility gene for BD is HLA-B*51 and that the association between MICA*009 and BD arises from a strong linkage disequilibrium with HLA-B*51. However, we suggest that MICA*009 likely elicits an immune effect secondary to BD.

HLA-B51 gene and its expression in association with Behçet’s Disease in Denizli Province of Turkey

Behçet's Disease (BD) is a multisystemic inflammatory disorder as a triad of symptoms including recurrent oral and genital aphthous ulceration, and uveitis with unknown pathogenesis. Many researchers have tried to investigate the association of HLA-B51 gene with the BD. We aimed to investigate the association of the HLA-B51 gene and its expression, also polymorphic structure by PCR, RT-PCR and sequence specific oligonucleotide primers and probes in BD patients (n: 35) and control group (n: 50). According to our results, we did not observe any association in between HLA-B51 gene, its polymorphism, expression and BD patients.

Linkage disequilibria between human leucocyte antigen-B and closely linked microsatellites in the Croatian population

The aim of the present study was to investigate polymorphism of D6S2927, STR_MICA, D6S2793, TNFa (D6S2792), TNFb and TNFd (D6S2789) microsatellites and linkage disequilibria between these loci and human leucocyte antigen (HLA)-B (previously tested) for better characterisation of extended HLA haplotypes. A total of 176 healthy unrelated Croatians were studied using polymerase chain reaction amplification and electrophoresis on 6% polyacrylamide gel in ALFexpress sequencer. Eight HLA-B/D6S2927 haplotypic associations (B*07/D6S2927-4, B*08/D6S2927-3, B*18/D6S2927-3, B*27/D6S2927-1, B*35/D6S2927-5, B*38/D6S2927-4, B*51/D6S2927-2 and B*61/D6S2927-1) showed strong association (P < 0.001, D > 0.5). Among 88 different HLA-B/STR_MICA haplotypic associations, seven combinations (B*07/STR_MICA-A5.1, B*08/STR_MICA-A5.1, B*15/STR_MICA-A5, B*18/STR_MICA-A4, B*27/STR_MICA-A4, B*38/STR_MICA-A9 and B*51/STR_MICA-A6) demonstrated high linkage (D> or = 0.3) with significant P value (P < 0.001). Strong associations were also observed for five HLA-B/D6S2793 haplotypes (B*07/D6S2793-CA17, B*08/D6S2793-CA24, B*13/D6S2793-CA18, B*14/D6S2793-CA14 and B*27/D6S2793-CA14). HLA-B*08/TNFb3 and HLA-B*50/TNFb7 were the strongest associations for HLA-B/TNFb. Nine HLA-B/TNFa combinations were observed with significant P value (B*07/TNFa11, B*08/TNFa2, B*13/TNFa7, B*18/TNFa10, B*27/TNFa6, B*37/TNFa9, B*38/TNFa10, B*39/TNFa13 and B*44/TNFa4). Out of six HLA-B/TNFd haplotypic associations with strong D value, HLA-B*08/TNFd2 and B*37/TNFd3 showed the highest statistical significance (P < 0.0001). These results provide data on the region around the HLA-B that is very attractive because of its contribution to genetic susceptibility for many HLA-associated diseases and therefore this information will help in all further HLA-B locus-associated disease studies.

Microsatellite polymorphisms of the MICA gene among Japanese patients with Behçet's disease

BACKGROUND

Behçet's disease (BD) is a multisystemic inflammatory disease of unknown origin. Because some researchers have recently suggested a primary association of BD with the A6 allele of the human major histocompatibility complex class I chain-related A (MICA) gene, we investigated microsatellite polymorphisms of the MICA gene in subjects with and without BD.

METHODS

This was a case-control study of 23 Japanese patients with BD and 23 Japanese volunteers without BD who were compared for MICA microsatellite polymorphisms using the polymerase chain reaction (PCR). We also analysed associations between 5 MICA alleles and the clinical features of patients.

RESULTS

There was no significant difference between case patients and control subjects in phenotype frequencies. The MICA-A6 allele showed the strongest positive correlation with the human leukocyte antigen allele HLA-B51. Allele A5 showed a strong positive correlation with age at onset and a strong negative correlation with iridocyclitis and HLA-B51. A4 showed a strong negative correlation with ocular lesions and HLA-B51. Patients with the MICA-A6 allele had significantly higher HLA positivity than patients without the allele.

INTERPRETATION

While the MICA-A6 allele had no significant association with BD, it showed a strong association with HLA-B51. This finding suggests that an association between MICA-A6 and BD may be a secondary phenomenon related to HLA-B51. As several associations with MICA alleles and clinical features have been found, further investigation is expected to elucidate the biological mechanism of action of the MICA protein relative to disease onset.

Chromosome and sister chromatid exchange studies in Behcet's patients

Behcet's disease is a chronic multisystemic disease of unknown pathogenesis characterized by four major symptoms: oral aphthous ulcers, skin lesions, ocular symptoms and genital ulcerations. The disease is spread throughout the world, but it is most frequent in Turkey, Japan, Korea and China. Although HLA-Bw51 has been found to predominate in Behcet's cases, the genetic etiology has not yet been clarified. In this study, we investigated the chromosomal abnormalities and sister chromatid exchange rates in patients with Behcet's diseases. Thirty-eight patients with Behcet's disease (diagnosed for the first time) and 30 healthy subjects (as controls) were included in this study. Although numerical and structural chromosomal abnormalities were not detected in our patients, we found an increased rate of sister chromatid exchange in patients over the control groups (P < 0.01). On the basis of these results, we discuss the genetic etiology of Behcet's disease.

Associations of major histocompatibility complex class I chain-related molecule polymorphisms with Behcet's disease in Caucasian patients

HLA-B*51 is known to be associated with Behcet's disease (BD) in many ethnic groups. The pathogenic gene, however, may lie close to the HLA-B locus and therefore be in linkage disequilibrium with HLA-B*51. On the basis of the proximity of MIC genes to HLA-B, their expression pattern and their affinity for the activating NKG2D receptor on natural killer (NK) cells and gammadelta T cells, these molecules have been postulated as susceptibility factors in BD. DNA from 56 western European Caucasians with BD and 90 Caucasian controls were analysed by polymerase chain reaction using allele-specific primers for MICA and MICB alleles. An increased allele frequency of MICA*009 was found in the BD patient group (25.0%) when compared with the controls (7.2%). This was associated with a corresponding decrease in MICA*008 in the BD patients (36.6%) compared with the controls (46.7%), which was not significant. MICA*009 was strongly associated with the presence of HLA-B*51 in patients and controls. No significant difference in frequency of MICB alleles was found between patients and controls. Both HLA-B*51 and MICA*009 are strongly associated with BD in a pure Caucasian BD patient group, and the two alleles are in linkage disequilibrium. No MICB allele was found to associate significantly with the disease, an unexpected finding considering the close proximity of the MICA and MICB loci. Our results suggest that while MICB does not influence the development of BD, polymorphisms in MICA may be pathogenic, perhaps through the interaction with NK and gammadelta T cells.

MHC class I chain-related gene A-A5.1 allele is associated with ulcerative colitis in Chinese population

The human MHC class I chain-related gene A (MICA) plays a role in regulating protective responses by intestinal epithelial Vdelta1 gamma delta T cells and the polymorphism of MICA were reported to be related to several autoimmune diseases. The present study aimed to investigate the association of the microsatellite polymorphisms of TM region of MICA gene with the susceptibility to ulcerative colitis (UC) in Chinese population. The microsatellite polymorphisms of the MICA were genotyped in unrelated 86 Chinese patients with UC and 172 ethnically matched healthy controls by a semiautomatic fluorenscently labelled PCR method. All the subjects were the Chinese with Han nationality. The frequency of MICA-A5.1 homozygous genotype and A5.1 allele were significantly increased in UC patients compared with healthy controls (22.1%versus 7%, P = 0.0009, Pc = 0.0126, OR = 3.781, 95%CI: 1.738-8.225 and 30.2%versus 17.4%, P = 0.0014, Pc = 0.007, OR = 2.051, 95%CI: 1.336-3.148, respectively). Adjusted the effects of gender and age at onset, MICA-A5.1 homozygous genotype and A5.1 allele were also increased in the UC patients. Moreover MICA-A5.1 allele was significantly increased in frequency in the female UC patients (38.2%versus 21.0%, P = 0.0095, Pc = 0.0475, OR = 2.326, 95%CI: 1.234-4.382). Logistic regression analysis also revealed that gender was independently associated with UC patients carried MICA-A5.1 allele (P = 0.046, OR (male) = 0.511, 95% CI: 0.264-0.987). Although the UC patients with extensive colitis (32.5%versus 17.4% in the healthy controls, P = 0.005, Pc = 0.025) and the UC patients with extraintestinal manifestations (36%versus 17.4% in the healthy controls, P = 0.0039, Pc = 0.0195) were more likely to carry the MICA-A5.1 allele, EIMs was associated with extent of disease (P < 0.0001, OR (with EIMs) = 3.511, 95% CI 1.747-7.056) and MICA-A5.1 allele was not associated with UC patients with extensive colitis or with EIMs in the logistic regression analysis. Therefore, the MICA-A5.1 homozygous genotype and A5.1 allele were closely associated with UC and the MICA-A5.1 allele was positively associated with the female UC patients in Chinese population.

Beh??et??s syndrome and the nervous system

PURPOSE OF REVIEW

Behçet's syndrome (BS) is a multi-system, vascular-inflammatory disease of unknown origin, involving the nervous system in a subgroup of patients. The syndrome is rare, but as patients with BS are young and frequently present with an acute or subacute brainstem syndrome or hemiparesis, as well as with other various neurological manifestations, the syndrome is often included in the differential diagnosis of multiple sclerosis, stroke of the young adult, and another wide range of neurological disorders. The present review summarizes the neurological involvement in BS, and emphasizes recent clinical concepts and ethiopathogenetic findings.

RECENT FINDINGS

Over the last years the growing clinical and imaging evidence had suggested that neurological involvement in BS may be subclassified into two major forms: one, which is seen in the majority of patients, may be characterized as a vascular-inflammatory CNS disease, with focal or multifocal parenchymal involvement; the other, which has few symptoms and a better neurological prognosis, may be caused by isolated cerebral venous sinus thrombosis and intracranial hypertension. These two types rarely occur in the same individual, and their pathogenesis is likely to be different. A nonstructural vascular type headache is relatively common, whereas isolated behavioral syndromes and peripheral nervous system involvement are rare.

SUMMARY

The involvement of the nervous system in BS is heterogeneous as clinical and imaging data reveal. Currently it is unknown which factors determine or have a role in the development of neurological involvement, but some progress has been achieved in understanding the neurological spectrum of the syndrome, which may lead to a better management of these patients.

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.

Behçet syndrome

PURPOSE OF REVIEW

Interest in Behçet syndrome (BS), although the condition is rare in many parts of the world, is increasing as judged by the growing number of related publications and scientific meetings.

RECENT FINDINGS

Recent work reconfirmed the following without further insight into their meaning in pathogenesis: males have a more severe course; one third of the patients have a thrombophilia; papulopustular lesions and arthritis go together; gammadelta T are increased; and HLA B51 is still the main genetic association. Presence of increased levels of antibodies to Saccharomyces cerevisiae and the proposal of alpha-enolase as the target antigen of antiendothelial cell antibodies, known to be present also in BS, are observations that might help in delineating the unknown pathogenesis. For management, preliminary yet promising experience with the use of anti-tumor necrosis factor agents is being reported. SUMMARY When compared with 2 decades ago, we know considerably more and can do more about BS.