MICA gene polymorphism in Takayasu's arteritis and Buerger's disease

Genetics of vasculitis

Systemic vasculitis encompasses a wide range of conditions characterized by varying degrees of inflammation in blood vessels. Although the etiology of vasculitis remains unclear, accumulated data suggest that it is triggered in genetically predisposed individuals by the concurrence of certain environmental factors. The importance of the genetic component has been consistently supported by evidence of familial aggregation, differential prevalence by ethnicity, and multiple genetic associations with disease susceptibility and severity reported in recent years. The strongest association signals in most vasculitides correspond to genetic variants within the HLA region, suggesting an important role of the immune system in its pathophysiology. However, each type of vasculitis has distinct defining HLA association markers, likely due to disease-specific differences in antigenic drivers. Furthermore, other genetic polymorphisms located outside the HLA region play an important role in susceptibility to different vasculitides. More recent research has assessed the shared genetic susceptibility evident across different vasculitides. Future studies should focus on the identification of genetic markers that can serve as reliable biomarkers for early diagnosis, prognosis, and treatment response in systemic vasculitis.

Association of MICA gene Exon-5 polymorphism in oral submucous fibrosis

OBJECTIVE

The present study was conducted to explore the allele frequencies of MICA gene Exon-5 transmembrane and to measure the circulatory MICA levels in various histologic grades of patients with oral submucous fibrosis (OSF) compared to healthy individuals.

STUDY DESIGN

We enrolled a total of 595 patients for this cross-sectional study and divided them into 2 groups: healthy controls (n = 320) and patients with OSF (n = 275). Further, patients with OSF were subdivided based on their histologic gradings. The genomic DNA was extracted followed by a polymerase chain reaction and genotyping using the ABI Prism DNA Sequencer (ThermoFisher Scientific, Inc., Waltham, MA, USA).

RESULTS

Our study showed that the A5 allele of the MICA gene in the Exon-5 region conferred significant risk for patients with OSF. With reference to the histologic gradings of OSF, we found that the MICA gene conferred statistically significant risk among patients with grade III OSF. On the other hand, the A8 allele of MICA gene in the Exon-5 region conferred significant protection among the overall OSF cohort and in the grade III of histologic grade. Finally, the circulatory human MICA levels were found to have a stepwise increase from grade I toward grade III in patients with OSF.

CONCLUSION

Our results suggested that the A5 allele in MICA might confer risk for the progression of OSF among the South Indian ethnic population.

Human leukocyte antigen class I (A, B) and class II (DRB1) allele and haplotype frequencies in Iranian patients with Buerger's disease

OBJECTIVE

The aim of this study was to investigate the human leukocyte antigen (HLA) class I (HLA-A and HLA-B) and II (HLA-DRB1) allele and haplotype frequencies in a group of Iranian patients with Buerger's disease (BD) in comparison with a normal healthy control group.

METHODS

A total of 70 unrelated male patients and 100 healthy controls from Sina Hospital, Tehran, Iran, belonging to the same ethnic background, were enrolled in this case-control study. HLA-A, B, and DRB1 typing were performed by polymerase chain reaction with sequence-specific primers (PCR-SSP).

RESULTS

The results of this case-control study showed that the frequency of the HLA-A*03:01 (odds ratio (OR) = 2.88, P value (Pv) = .002), HLA-A*29:01 (OR = 15.31, Pv < .001), HLA-DRB1*04:02 (OR = 3.41, Pv < .001), and HLA-DRB1*16:01 (OR = 8.16, Pv < .001) was significantly higher in BD patients compared with healthy controls, whereas the frequency of the HLA-DRB1*01:01 (OR = 0.03, Pv < .001) was significantly lower in BD patients. The most frequent extended haplotypes in our patients were HLA-A*02:01-B*55:01-DRB1*04:03.

CONCLUSION

This study is the first study evaluating an association between the HLA pattern and BD in the patients with BD from North West and North Iran.

Effects of aspirin combined with cilostazol on thromboangiitis obliterans in diabetic patients

The present study explored the effects of aspirin combined with cilostazolin in the treatment of diabetic patients with thromboangiitis obliterans and the effects on the related inflammatory factors. A total of 90 diabetic patients with thromboangiitis obliterans admitted to Weifang People's Hospital from August 2015 to June 2017 were selected and divided into the control group (n=45) and the combination group (n=45). Patients in the control group were given aspirin, and those in the combination group were given aspirin combined with cilostazol. Before treatment and 6 weeks after treatment, the clinical data including ankle-brachial index (ABI), 6-min walk test (6MWT) and test data including serum inflammatory factors interleukin (IL)-8, IL-6 and matrix metalloprotease (MMP)-2 and MMP-9 of the two groups were collected for quantitative and statistical analysis. Compared with those in the control group, the ABI and 6MWT in the combination group could be effectively reduced, and the differences were statistically significant (P<0.05). At the same time, cilostazol combined with aspirin could effectively reduce the levels of serum inflammatory factors MMP-2 and MMP-9 in patients, except for nitric oxide (NO), and the differences were statistically significant (P<0.05). Compared with that before treatment, the control and the combination group can significantly improve the clinical symptoms of the patients, and aspirin combined with cilostazol can effectively improve the clinical curative effect of diabetic patients with thromboangitis obliterans and delay the progression of the disease.

The genetics of Takayasu arteritis

Takayasu arteritis (TAK) is a rare systemic vasculitis that is characterized by granulomatous inflammation of the aorta and its major branches. The cellular and biochemical processes involved in the pathogenesis of TAK are beginning to be elucidated, and implicate both cell and antibody-mediated autoimmune mechanisms. In addition, the underlying etiology to TAK may be explained, at least in part, by a complex genetic contribution. The most well-recognized genetic susceptibility locus for the disease is the classical HLA allele, HLA-B*52, which has been confirmed in several ethnicities. The genetic susceptibility with HLA-B*52, as well as additional classical alleles and loci, implicate both HLA class I and class II involvement in TAK. Furthermore, genetic associations with genes encoding immune response regulators, pro-inflammatory cytokines and mediators of humoral immunity may directly relate to disease mechanisms. Non-HLA susceptibility loci that have been recently established for TAK with a genome-wide level of significance include FCGR2A/FCGR3A, IL12B, IL6, RPS9/LILRB3, and a locus on chromosome 21 near PSMG1. In this review, we present the complex genetic predisposition to TAK and discuss how recent findings identified potential targets in the pathogenesis and treatment of the disease.

Buerger's disease: providing integrated care

Buerger’s disease, also known as thromboangiitis obliterans (TAO), is a segmental inflammatory disease affecting small- and medium-sized vessels, which is strongly associated with tobacco use. Although the etiology is still unknown, recent studies suggest an immunopathogenesis. Diagnosis is based on clinical and angiomorphologic criteria, including age, history of smoking, clinical presentation with distal extremity ischemia, and the absence of other risk factors for atherosclerosis, autoimmune disease, hypercoagulable states, or embolic disease. Until now, no causative therapy exists for TAO. The most important therapeutic intervention is smoking cessations and intravenous prostanoid infusions (iloprost). Furthermore, effective analgesia is crucial for the treatment of ischemic and neuropathic pain and might be expanded by spinal cord stimulation. Revascularization procedures do not play a major role in the treatment of TAO due to the distal localization of arterial occlusion. More recently, immunoadsorption has been introduced eliminating vasoconstrictive G-protein-coupled receptor and other autoantibodies. Cell-based therapies and treatment with bosentan were also advocated. Finally, a consequent prevention and treatment of wounds and infections are essential for the prevention of amputations. To achieve better clinical results, integrated care in multidisciplinary and trans-sectoral teams with emphasis on smoking cessation, pain control, wound management, and social care by professionals, social workers, and family members is necessary.

Revisited HLA and non-HLA genetics of Takayasu arteritis--where are we?

Takayasu arteritis (TAK) is an immune-mediated vasculitis affecting large arteries first reported in 1908 from Japan. Case reports of familial onset of TAK from Japan and other countries indicated genetic contribution to TAK onset beyond ethnicity. Genetic studies of TAK have been performed mainly addressing the human leukocyte antigen (HLA) locus. HLA genetic studies of TAK that have previously been reported are reviewed in this manuscript. HLA-B*52:01 is associated with TAK beyond population. Many of the associations other than HLA-B*52:01 can be explained by a haplotype with HLA-B*52:01. HLA-B*67:01 is a novel susceptibility HLA-B allele to TAK confirmed in the Japanese population. Further independent associations are suggested in the HLA locus. Involvement of the 171st and 67th amino acid residues with TAK onset has been indicated. The 67th amino acid may explain the difference in susceptibility effects to TAK and Behçet's disease between HLA-B*52:01 and *51:01. HLA-B*52:01 is associated not only with TAK susceptibility but also with clinical phenotypes. Recent genome-wide association studies of TAK revealed multiple non-HLA susceptibility genes. In particular, the IL12B region seems to have a central role in TAK onset and its progression. Whether TAK and giant cell arteritis (GCA), the other vasculitis affecting large arteries, are the same disease is an interesting question to address in spite of different clinical manifestations between the two diseases. GCA is associated with HLA-DR4, which is not associated with TAK. GCA is not associated with HLA-Bw52. These two diseases seem not to share non-HLA susceptibility loci based on the recent genetic studies.

NKG2D stimulated T-cell autoreactivity in giant cell arteritis and polymyalgia rheumatica

OBJECTIVE

To investigate functional expression of NKG2D on CD4 and CD8 T-cells in patients with giant cell arteritis (GCA) and polymyalgia rheumatica (PMR).

METHODS

Peripheral blood was drawn from patients with GCA (n=16), PMR (n=78) and healthy controls (HC, n=64). Tissue samples were obtained from GCA patients and controls. Proliferation and cytokine production assays were performed using CFSE and intracellular IFN-γ or TNF-α staining, respectively, and flow cytometry analysis. Immunofluorescence and immunohistology were applied to analyse the presence of NKG2D-expressing T-cells and NKG2D-ligands in temporal arteries, respectively. mRNA levels of NKG2D-ligands were determined by RT-PCR.

RESULTS

In both GCA and PMR patients, NKG2D was preferentially expressed on senescent CD4CD28(-) and CD8CD28(-), as well as on CD8CD28 T-cells. Frequencies of senescent T-cells were increased in GCA and PMR patients compared to HC. In GCA tissue samples, infiltrating T-cells were predominately CD28(-). NKG2D expressing T-cells concentrated around the vasa vasorum of the adventitia. Antigenic stimulation induced rapid up-regulation of NKG2D on CD4CD28(-) and CD4CD28 T-cells, whereas TNF-α and interleukin-15 enhanced NKG2D expression on senescent CD4 and CD8 T-cells only. NKG2D cross-linkage augmented anti-CD3 triggered proliferation, IFN-γ and TNF-α production of CD8 T-cells. In CD4CD28(-) T-cells, NKG2D ligation resulted in increased IFN-γ production only. NKG2D ligands were expressed in temporal arteries from GCA patients, particularly in the adventitial and medial layers of affected vessels.

CONCLUSIONS

NKG2D is functionally expressed on CD4CD28(-) and CD8 T-cells in GCA and PMR. NKG2D-ligands are present in temporal arteries and may co-stimulate NKG2D expressing T-cells.

Impaired endothelial-dependent and endothelium-independent vasodilatation in patients with thromboangiitis obliterans

BACKGROUND

Endothelial dysfunction is the key process in the development of atherosclerosis. The aim of our study was to evaluate endothelial dysfunction measured by the noninvasive technique of Celermajer that plays a role in the pathogenesis of thrombangitis obliterans.

METHODS

A total of 36 patients with thrombangitiis obliterans ([TAO]; mean age 44.9 ± 1.3 years) were compared with 30 healthy individuals (mean age 36.1 ± 1.8 years). High frequency ultrasound was used to measure changes in response to reactive hyperemia (leading to flow-mediated endothelium-dependent dilatation) and in response to 0.4 mg sublingual nitroglycerin ([NTG]; leading to NTG-induced, endothelium-independent dilatation).

RESULTS

Patients with TAO showed a lower but statistically not significant flow-mediated dilatation and a statistically significant reduced NTG-induced vasodilatation than the control group.

CONCLUSION

Our results suggest that both mechanisms play a role in patients with TAO, the endothelium-independent impaired vasodilatation even in a more significant way than the impaired endothelium-dependent vasodilatation.

Takayasu's arteritis is associated with HLA-B*52, but not with HLA-B*51, in Turkey

Introduction

HLA-B*51 and HLA-B*52 are two close human leukocyte antigen (HLA) allele groups with minor amino acid differences. However, they are associated with two different vasculitides (HLA-B*51 in Behçet's disease and HLA-B*52 in Takayasu's arteritis (TAK)) and with major clinical and immunological differences. In this study, we aimed to screen a large cohort of TAK patients from Turkey for the presence of HLA-B*51 and HLA-B*52 as susceptibility and severity factors.

Methods

TAK patients (n = 330) followed at a total of 15 centers were included in the study. The mean age of the patients was 37.8 years, and 86% were women. DNA samples from the patients and healthy controls (HC; n = 210) were isolated, and the presence of HLA-B*51 or HLA-B*52 was screened for by using PCR with sequence-specific primers.

Results

We found a significant association of HLA-B*52 with TAK (20.9% vs HC = 6.7%, P = 0.000, OR = 3.7, 95% CI = 2.02 to 6.77). The distribution of HLA-B*51 did not differ between TAK patients and HCs (22.7% vs 24.8%, OR = 0.9, 95% CI = 0.60 to 1.34). The presence of HLA-B*52 decreased in late-onset patients (> 40 years of age; 12.0%, P = 0.024, OR = 0.43, 95% CI = 0.20 to 0.91). Patients with angiographic type I disease with limited aortic involvement also had a lower presence of HLA-B*52 compared to those with all other disease subtypes (13.1% vs 26%, P = 0.005, OR = 0.43, 95% CI = 0.23 to 0.78).

Conclusions

In this study, the previously reported association of TAK with HLA-B*52 in other populations was confirmed in patients from Turkey. The functional relevance of HLA-B*52 in TAK pathogenesis needs to be explored further.

A single nucleotide polymorphism in the 3'-untranslated region of MyD88 gene is associated with Buerger disease but not with Takayasu arteritis in Japanese

Buerger disease (BD) and Takayasu arteritis (TA) are rare vascular disorders. Although their etiology and pathogenesis have not been elucidated, several studies have suggested the involvement of innate immunity. Myeloid differentiation primary-response protein 88 (MyD88) is a key signaling adaptor for all Toll-like receptors, which have a central role in innate immunity. In the present study, we evaluated the association of MyD88 with BD and TA. We conducted case-control studies in Japanese populations composing of 131 BD cases, 90 TA cases and 270 healthy controls to be genotyped for a single nucleotide polymorphism rs7744 A>G in the 3'-untranslated region of MyD88 gene. The frequency of GG genotype was significantly lower in the BD patients than in the controls (6.9 vs 15.9%, P=0.011, odds ratio=0.39, 95% confidence interval; 0.19, 0.81), although there was no significant difference in the genotype frequencies between the TA patients and controls. It was suggested that MyD88 may confer resistance to BD in Japanese. Because this is the first report of the association between MyD88 and BD, replication studies in other cohorts are required.

Synergistic contribution of CD14 and HLA loci in the susceptibility to Buerger disease

Buerger disease (BD) is an occulusive vascular disease of unknown etiology. Although cigarette smoking is a well-known risk factor of BD, genetic factors may also play a role in the etiology. Because chronic bacterial infection such as oral periodontitis is suggested to be involved in the pathogenesis of BD, gene polymorphisms involved in the infectious immunity might be associated with BD as the genetic factor(s). We have previously reported that HLA-DRB1*1501 and B54 was associated with BD in Japanese. In this study, polymorphisms in HLA-DPB1, DRB1 and B were analyzed in 131 Japanese BD patients and 227 healthy controls. In addition, we investigated a functional promoter polymorphism, -260 C > T, of CD14 that is a main receptor of bacterial lipopolysaccharide. It was found that the frequencies of CD14 TT genotype [37.4 vs. 24.2%, P = 0.008 OR = 1.87, 95% confidence interval (CI); 1.18, 2.97], DRB1*1501 (34.4 vs. 13.2%, P (c) = 4.4 x 10(-5), OR = 3.44, 95%CI; 2.06, 5.73) and DPB1*0501 (79.4 vs. 55.1%, P (c) = 4.7 x 10(-5), OR = 3.14, 95%CI; 1.93, 5.11) were significantly higher in the patients than in the controls, demonstrating that at least three genetic markers were associated with BD. Stratification analyses of these associated markers suggested synergistic roles of the genetic factors. Odds ratios ranged from 4.72 to 12.57 in individuals carrying any two of these three markers. These findings suggested that the susceptibility to BD was in part controlled by genes involved in the innate and adaptive immunity.

Multiple complications due to osteoradionecrosis in a patient with thromboangiitis obliterans

A case is presented of a patient with thromboangiitis obliterans (TAO) who developed severe necrosis of the intraoral soft tissues and maxillary and mandibular bone after radiotherapy for a cT2N0M0 squamous cell carcinoma of the soft palate. Multiple surgical procedures including partial resection of the mandible and maxilla and reconstruction of intraoral and extraoral defects with a pectoralis major myocutaneous flap and anterolateral thigh flap were performed with partial success. Although a causal relationship between TAO and the described complications cannot be verified, close monitoring of patients with TAO who are being treated with radiotherapy is advised.

Different immunophenotypes in Buerger's disease

Recently, we reviewed the morphology of 31 specimens of thromboangiitis obliterans (TAO, Buerger's disease) in a multivariate analysis and showed that certain novel features of the affected vessels are different from arteriosclerosis obliterans (ASO) and thromboembolism. However, the pathogenic concept of TAO is still controversial. We applied immunohistochemistry to 58 amputated lower extremities and five autopsy controls. At specific sites of the diseased vessels, different cellular components were immunotyped by CD3, CD4, CD20, CD31, CD68, actin and desmin. These results were carefully compared among different diagnostic groups of vasoocclusive lesions by statistical methods. Some unique characteristics of TAO were identified when compared with ASO or thromboembolism. Consistent with a primary inflammatory and immunogenic lesion, lymphocytes and especially CD4+ T cells emerged significantly in TAO vessels and their adventitia. In the subset of definite TAO cases defined by all clinical criteria, the linear arrangement of macrophages, and B- and T-lymphocytes along vascular elastic fibers was the most striking additional finding, suggesting elastic fibers are an important immunogen. However, this feature was not apparent in closely related cases, otherwise similar to TAO and different from ASO and thromboembolism. Thus, our results indicate a heterogeneous group of TAO diseases, suggesting that damage to elastic fibers may be a secondary change to primary inflammation.

MICA and MICB microsatellite alleles in HLA extended haplotypes

The present study is a contribution to the definition of the linkage disequilibrium relationship of MICA and MICB with adjacent loci and to the characterization of extended HLA haplotypes. These issues are of importance for the identification of disease associations and for a better definition of donor-recipient compatibility in bone-marrow grafts through the typing of haplospecific markers. The distribution of the five alleles of MICA and the 13 alleles of MICB microsatellites, located, respectively, in MICA transmembrane exon 5 and in MICB intron 1, was examined in 133 healthy Italian individuals previously typed for HLA class I, class II and complement loci and for the TNFa microsatellite. The MICB microsatellite was also analysed in 49 HTCLs for which MICA typing was already available. Very strong linkage disequilibria with HLA-B and TNFa were detected in the Italian population for both MICA and MICB microsatellite alleles, in spite of the high mutability rate of the larger MICB alleles. Some strong associations were also detected between MICB and DRB1. The strongest associations (P < 0.001, D' > 0.7) were those of MICA-A4 with HLA-B18, B27 and TNFa1, MICA-A5 with HLA-B35, B61 and B62, MICA-A5.1 with HLA-B7, B8, B13, B63 and MICB-CA24, MICA-A6 with HLA-B51, MICA-A9 with HLA-B39, B57 and TNFa2, MICB-CA14 with HLA-B14, B27 and TNFa1, MICB-CA15 with HLA-B52, TNFa4 and TNFa13, MICB-CA17 with HLA-B7 and TNFa11, MICB-CA18 with HLA-B13 and TNFa7, MICB-CA22 with HLA-B57, and MICB-CA24 with HLA-B8 and TNFa2. From pairwise associations in the random panel and results for the homozygous cell lines it was possible to deduce the MICA and MICB microsatellite alleles present in many of the well-known Caucasoid extended haplotypes.

Identification of MICA alleles with a long Leu-repeat in the transmembrane region and no cytoplasmic tail due to a frameshift-deletion in exon 4

MHC class I chain-related gene A (MICA) is located close to HLA-B gene and expressed in epithelial cells. The MICA gene is reported to be highly polymorphic as are the classical class I genes. To further assess the polymorphism in the MICA gene, we analyzed a total of 60 HLA-homozygous cells for the sequences spanning exons 2-6. In the analysis, four new MICA alleles were identified and six variations were recognized in exon 6. MICA*017, which was identified in three HLA-B57 homozygous cells (DBB, DEM and WIN), differed from MICA*002 in exon 3 and had a guanine deletion at the 3' end of exon 4. MICA*015 identified in an HLA-B45 homozygous cell (OMW) also had the same deletion that causes a frameshift mutation resulting in complete change of the transmembrane region and premature termination in the cytoplasmic tail; these alleles have a long hydrophobic leucine-rich region instead of the alanine repeat in the transmembrane region and terminate at the second position in the cytoplasmic domain. The frameshift deletion was found only in HLA-B45- or -B57-positive panels tested, suggesting a strong linkage disequilibrium between the deletion and B45 or B57. MICA*048, which was different in exon 5 from MICA*008, was identified in an HLA-B61 homozygous cell (TA21), while MICA*00901 identified in HLA-B51 homozygous cells (LUY and KT2) was distinguished from MICA*009 by exon 6.

Mapping MHC-encoded susceptibility and resistance in primary sclerosing cholangitis: the role of MICA polymorphism

BACKGROUND & AIMS

Recent studies suggest that major histocompatibility complex-encoded susceptibility to primary sclerosing cholangitis (PSC) maps to the HLA B-TNFA region on chromosome 6p21.3.

METHODS

The present study uses a standard polymerase chain reaction protocol to investigate the 16 common alleles of the MICA locus as candidates in 2 patient populations (King's College Hospital, London, and John Radcliffe Hospital, Oxford).

RESULTS

The MICA*002 allele was found in 4 of 62 (6.4%) patients and none of 50 patients vs. 41 of 118 (35%) controls (pc = 0.00018, odds ratio [OR] = 0.12, and P = 0.0000016, OR = 0.0, respectively). Overall, the MICA*008 allele was more common in PSC (gene frequency 66% vs. 48% of controls, P = 0.0023, OR = 2.11). However, unlike MICA*002 in which the difference was a result of the absence of MICA*002 heterozygotes, the MICA*008 association may be caused by an increased frequency of MICA*008 homozygosity in patients (58% vs. 22%, pc = 0.000015, OR = 5.01 and 58% vs. 22%, P = 0.0000056, OR = 4.51, respectively). Though MICA*008 is found on the ancestral 8.1 haplotype, stratification analysis indicates that this association is independent of B8 and other HLA haplotypes associated with PSC.

CONCLUSIONS

The MICA*002 allele has a strong dominant effect in reducing the risk of PSC, whereas the increased risk of disease associated with MICA*008 may be a recessive effect requiring 2 copies of the MICA*008 allele.

Lack of association between the Met196Arg polymorphism in the TNFR2 gene and autoimmune diseases accompanied by vasculitis including SLE in Japanese

A polymorphism in high-affinity receptor of TNF (TNFR2) gene, Met196Arg, was reported to be associated with systemic lupus erythematosus (SLE) in Japanese, whereas the association could not be found in Europeans at all and this represents an apparent discrepancy. The association, then, should be tested in other populations to clarify the possible involvement, if any, of the TNFR2 polymorphism in SLE or other related autoimmune diseases. The purposes of this study were to examine the TNFR2 polymorphism in Japanese patients with SLE and to investigate its association with other autoimmune diseases accompanied by vasculitis, mixed connective tissue disease, Buerger's disease, and Takayasu's arteritis. We found no association at all between the TNFR2 polymorphism and any autoimmune diseases including SLE in Japanese.

Vasa vasoritis, vasculitis and atherosclerosis

Takayasu arteritis, Buerger's diseases, temporal arteritis, vascular Behcet disease and inflammatory abdominal aortic aneurysm are classified in Japan as intractable vasculitides involving mainly large vessels, because their etiologies are not yet elucidated and, therefore, treatments for them were not yet established. Recent experimental and vascular biological studies, however, have focussed on the roles of virus infection in vasa vasorum (vasa vasoritis) and on the subsequent inflammatory vascular changes through HLA and/or other autoimmune mechanisms. Several studies including ours have demonstrated that these vascular inflammatory changes progress from the adventitial side to the intimal side of the vessel, finally complicating atherosclerotic changes in the intima. These vascular inflammatory changes are also recognized during progression of atherosclerosis and these observations strongly suggest that inflammation is a serious risk factor of atherosclerosis.

Restricted usage of T-cell receptor Vgamma-Vdelta genes and expression of costimulatory molecules in Takayasu's arteritis

To further investigate the immunological mechanisms involved in Takayasu's arteritis, we analyzed the T-cell receptor (TCR) Vgamma and Vdelta gene usage by infiltrating gammadelta T-cells and the expression of costimulatory molecules B7-1, B7-2, CD40, CD27 ligand (CD27L), CD30L, OX40L in the arterial tissue of a patient with Takayasu's arteritis. We found that the repertoires of TCR Vgamma as well as Vdelta gene transcripts of the infiltrating cells were restricted as compared with those of peripheral blood lymphocytes from a patient with Takayasu's arteritis. This strongly suggests that gammadelta T-cells as well as alphabeta T-cells, as we previously reported, were specifically involved in the pathogenesis of Takayasu's arteritis. We also found that B7-1, B7-2, CD40, CD27L, CD30L, and OX40L were expressed in the arterial tissue, suggesting the roles for these costimulatory molecules in T-cell-mediated vascular injury in Takayasu's arteritis. Our findings strongly support the involvement of T-cell-mediated immunological mechanisms in the pathogenesis of Takayasu's arteritis.

Mapping of the HLA-linked genes controlling the susceptibility to Takayasu's arteritis

To further define the HLA-linked genes controlling the susceptibility to Takayasu's arteritis, polymorphisms in five microsatellites around the HLA-B and MICA genes, C1-2-A, MIB, C1-4-1, C1-2-5, and C1-3-1, were investigated in 91 Japanese patients with Takayasu's arteritis and 248 healthy Japanese controls. It was found that allele 238 of C1-2-A [60.4% in patients vs. 29.8% in controls, odds ratio (OR)=3.59, P(c)<0.000004], allele 332 of MIB (22.0% vs. 6. 1%, OR=4.32, P(c)<0.0003), allele 208 of C1-2-5 (47.3% vs. 24.6%, OR=2.75, P(c)=0.001), and allele 291 of C1-3-1 (62.6% vs. 44.8%, OR=2.07, P(c)<0.02) were significantly associated with the disease. Combined analyses of polymorphisms in the HLA-B and MICA genes with those in the microsatellites suggest that there are two different disease-susceptible loci for Takayasu's arteritis; one is mapped near the C1-2-A locus and the other is more closely linked to the HLA-B gene than to the MICA gene, because there are at least two different disease-associated HLA-B haplotypes, HLA-B*52 and -B*39.2 haplotypes, in which the disease-associated C1-2-A allele is shared in common.