CTLA4+49G allele associates with early onset of type 1 diabetes in North Indians.

Type 1 diabetes (T1D) is a complex autoimmune disease with strong genetic influence. In this study, we investigated +49A/G SNP (rs 231775) in exon 1 of cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) by PCR-RFLP and its influence as a risk factor for the disease in the North Indian population. This polymorphism at codon 17 results in an amino acid substitution (Thr/Ala) in the leader peptide of the molecule. The study included 232 patients with T1D (age at onset of disease (AOD): 0.5-37 years) and 305 ethnically matched healthy controls. The DNA obtained from these 537 individuals was amplified using a set of specific primers followed by restriction enzyme digestion with Fnu4HI. The +49G allele as well as its homozygous genotype G/G was observed to be significantly higher in patients as compared to the healthy controls {(37.3% vs. 25.6%, P = 4.96E(-05) , OR = 1.73; 95%CI = 1.33-2.25) (15.52% vs. 6.6%, P = 0.001, OR = 2.62; 95% CI = 1.48-4.63) respectively}. The frequency of G/G genotype was significantly higher in patients with early age at onset of disease (AOD:<12 years) as compared to that in the late-onset patients with AOD: ≥12 years (21.1% vs. 10.6%, P = 0.042, OR = 2.26; 95% CI = 1.09-4.67) as well as to that in the healthy controls (21.1% vs. 6.6%, P = 0.00004, OR = 3.8; 95% CI = 2.01-7.2). Further analysis revealed that the median AOD significantly reduced (P = 0.049) from 14 years in patients with A/A genotype to 11 and 10 years in those with A/G and G/G genotypes, respectively. These results suggest that CTLA4+49G allele, particularly in homozygous G/G condition, associates with early onset of T1D.

Association of PTPN22+1858C/T polymorphism with Type 1 diabetes in the North Indian population.

A nonsynonymous SNP +1858C/T (rs2476601) in the protein tyrosine phosphatase, nonreceptor type 22(PTPN22) gene leading to Arg 620 Trp substitution is known to be associated with susceptibility to type 1 diabetes (T1D) and several other autoimmune diseases. We studied this polymorphism in 145 T1D patients and 210 healthy controls from North India. The minor allele +1858T was observed to be significantly increased among patients as compared to healthy controls (2.76% vs 0.5%, P = 0.027, OR = 5.93; 95% CI = 1.4-24.8). The association was also observed at the level of heterozygous C/T genotype (5.5% vs 0.95%, P = 0.026, OR = 6.07; 95% CI = 1.43-25.6). The T allele and C/T genotype were predominantly found among patients who were positive for both glutamic acid decarboxylase 65 (GAD65) and insulin antigen 2 (IA2) autoantibodies and showed significantly increased frequencies (10%, P = 0.034, OR = 11.67; 95% CI = 1.58-84.1 and 20%, P = 0.031, OR = 13.0; 95% CI = 1.66-97.5, respectively) as compared to patients negative for these autoantibodies (0.95% and 1.9%, respectively). The results suggest that the PTPN22+1858T allele is positively associated with T1D in the North Indian population.

16(th) IHIW: analysis of HLA population data, with updated results for 1996 to 2012 workshop data (AHPD project report).

We present here the results of the Analysis of HLA Population Data (AHPD) project of the 16th International HLA and Immunogenetics Workshop (16IHIW) held in Liverpool in May-June 2012. Thanks to the collaboration of 25 laboratories from 18 different countries, HLA genotypic data for 59 new population samples (either well-defined populations or donor registry samples) were gathered and 55 were analysed statistically following HLA-NET recommendations. The new data included, among others, large sets of well-defined populations from north-east Europe and West Asia, as well as many donor registry data from European countries. The Gene[rate] computer tools were combined to create a Gene[rate] computer pipeline to automatically (i) estimate allele frequencies by an expectation-maximization algorithm accommodating ambiguities, (ii) estimate heterozygosity, (iii) test for Hardy-Weinberg equilibrium (HWE), (iv) test for selective neutrality, (v) generate frequency graphs and summary statistics for each sample at each locus and (vi) plot multidimensional scaling (MDS) analyses comparing the new samples with previous IHIW data. Intrapopulation analyses show that HWE is rarely rejected, while neutrality tests often indicate a significant excess of heterozygotes compared with neutral expectations. The comparison of the 16IHIW AHPD data with data collected during previous workshops (12th-15th) shows that geography is an excellent predictor of HLA genetic differentiations for HLA-A, -B and -DRB1 loci but not for HLA-DQ, whose patterns are probably more influenced by natural selection. In Europe, HLA genetic variation clearly follows a north to south-east axis despite a low level of differentiation between European, North African and West Asian populations. Pacific populations are genetically close to Austronesian-speaking South-East Asian and Taiwanese populations, in agreement with current theories on the peopling of Oceania. Thanks to this project, HLA genetic variation is more clearly defined worldwide and better interpreted in relation to human peopling history and HLA molecular evolution.

Role of killer immunoglobulin-like receptor-ligand interactions in human leukocyte antigen-matched sibling hematopoietic stem cell transplantation.

INTRODUCTION: Killer immunoglobulin-like receptor (KIR)-ligand mismatches lead to natural killer cell alloreactivity after hematopoietic stem cell transplantation (HSCT). However, their clinical impact on HSCT outcomes is controversial due to complexity of KIR haplotypes, genotypes, and phenotypes as well as their diversity among patient populations. The present study investigated the role of KIR-ligand interactions in human leukocyte antigen (HLA)-matched sibling transplants. METHODS: The recipient cohort, which included patients diagnosed with aplastic anemia, acute leukemia, and myelodysplastic syndrome, received granulocyte-colony stimulating factor (G-CSF)-mobilized peripheral blood stem cells. HLA typing was performed using polymerase chain reaction - sequence specific oligo probes (PCR-SSO). The KIR genotype of the donors and the ligands C1 (Asparagine 80), C2 (Lysine 80), and Bw4 recipient typings were performed using polymerase chain reaction - sequence specific primers (PCR-SSP). We assessed acute and chronic graft-versus-host disease (GVHD), relapse, and overall survival. RESULTS: While 84.5% of donors carried a Bx KIR, 15.5% carried the AA haplotype. The effect of a recipient's lack of ligands among 88.5% of cases was associated with 39% of subjects developing GvHD. Lack of C1 may lead to manifestations of acute GvHD and lack of C2 to manifestation of chronic GvHD. The presence of both C1 and C2 seemed to be protective against both forms of GvHD. The role of two Bw4 alleles, threonine (T) or isoleucine (I) at position 80, was evaluated. 73% of recipients who carried Bw4 80(I) versus 27% with the Bw4 80(T) allele. The presence of Bw4-80(T) allele appeared to reduce the risk of GvHD, indicating its stronger inhibitory effect than its 80(I) counterpart. CONCLUSION: KIR-ligand interactions influenced HSCT outcomes.

Audit of peripheral stem cell transplantation for aplastic anemia in multitransfused infected patients.

INTRODUCTION: Allogeneic hematopoietic stem cell transplantation is a curative modality for aplastic anemia; the preferred stem cell source is bone marrow. However, allogeneic peripheral blood stem cell transplantation (PBSCT) used in high-risk patients is associated with higher risk of chronic graft-versus-host disease (GVHD). Our center receives multitransfused, alloimmunized, infected, late referrals for transplant. METHODS: Forty-one patients of median age 22 years (range 8-37) received allogeneic-PBSCT from human leukocyte antigen (HLA)-matched sibling donors. The median time since diagnosis was 12 months (range 4-65) and median pretransplant transfusions were 37 (range 6-160). Six patients were platelet refractory and one alloimmunized for pan-red blood cell (RBC) antigens. Several patients had pretransplant icterus or renal dysfunction and 26 (63.4%) had unresponsive bacterial/fungal infections. Our conditioning regimen included fludarabine 30 mg/m(2) for 6 days (days -10 to -5), cyclophosphamide 60 mg/kg/d for 2 days (days -6 to -5), and antithymocyte globulin (ATGAM) 30 mg/kg/d for 4 days (day -4 to -1), which was reduced to 2 days in 2 patients. We used standard GVHD prophylaxis with cyclosporine and methotrexate on days 1, 3, 6, 11. RESULTS: The median follow-up period was 29 months (range 6-78) and median engraftment time 10 days (range 8-17). Thirty-one patients (75.6%) were treated for infections, with 20 of these on antifungals for preexisting infections. There were two graft rejections and 10 (24.4%) deaths, with three intracranial hemorrhages, two rejections with infection, three cases of refractory GVHD (acute/overlap syndrome) with cytomegalovirus reactivation, and two invasive fungal infections. Overall incidence of acute GVHD was 39% with 2 grade IV cases. Ten (25%) cases developed chronic GVHD, with extensive GVHD in four. CONCLUSION: With more experience using shortened course of ATGAM, HLA-matched donor transfusions, and availability of newer antifungals, we have been able to decrease PBSCT-related mortality. Further improvement will be possible with early referrals.

A novel HLA-DPB1 allele, DPB1*125:01, identified by sequence-based typing in an Indian individual.

A novel DPB1*125:01 allele differs from DPB1*26:01:02 at two positions in exon 2, leading to changes at codons 9 and 35.

Asian Indian donor marrow registry: All India Institute of Medical Sciences experience.

A major limitation in hematopoietic stem cell transplantation (HSCT) is the availability of a genetically matched donor, particularly with respect to the human leukocyte antigens (HLA)-linked immune response genes located on chromosome 6 in humans. During the last 5 years, a total of 688 patients requiring HSCT underwent HLA testing in our department to identify a matched donor from their families. The sibship size ranged from 1 to > or =5 in all disease categories, except thalassemia major where the majority of patients had only 1 sibling. Family genotype analysis revealed that 39.3% of the total number of patients had an HLA-matched sibling and that families with sibship size of > or =4 had a higher probability (68.8%) compared with those with sibship size of < or =3 (29.7%). Because the Indian population is characterized by the presence of novel HLA alleles and unique haplotypes (HLA-A*0211, B*2707, A*26-B*08-DRB1*03), patients with rare HLA alleles have much less probability of finding an unrelated optimally matched donor than those with common HLA phenotypes. Smaller family size and unique HLA profile are limitations that can be overcome by developing unrelated volunteer marrow donor registries. The Asian Indian Donor Marrow Registry at our institute is regularly providing services to such patients.

Immunogenetic association and thyroid autoantibodies in juvenile autoimmune thyroiditis in North India.

OBJECTIVES: Autoimmune thyroid diseases (AITD) encompass a number of conditions that have in common cellular and humoral responses targeting the thyroid gland. Interactions between susceptibility genes and environmental triggers are thought to initiate an autoimmune response to thyroid antigens leading to disease manifestation. Commencement of the disease in childhood leads to the presumption that genetics may have an important role in the causation of the disease. DESIGN: The present study was aimed at evaluating the human leucocyte antigen (HLA) encoded susceptibility to develop juvenile autoimmune thyroiditis (JAT) in patients from North India. PATIENTS: We studied 48 consecutive patients of JAT along with 176 first-degree relatives for their thyroid function (FT4, TSH) and anti-thyroid peroxidase antibody status (AbTPO). MEASUREMENTS: HLA studies were carried out using serology for HLA-class I antigens and DNA analysis of HLA-class II alleles. The data were compared with a cohort of 308 ethnically matched healthy individuals. RESULTS: We observed overt hypothyroidism in 50% and AbTPO positivity in 70.8% of the index cases. Among the first-degree relatives, goitre was observed in 51.7%, thyroid dysfunction in 28.4% and AbTPO in 29.5% of individuals. Of the 37 relatives who underwent fine-needle aspiration cytology (FNAC), 60% had evidence of chronic lymphocytic thyroiditis (CLT). A strong positive association of HLA-DRB1*1404 was observed with the JAT (35.4%vs. 10.4%, chi2 = 19.8, Pc = 0.0001). We also observed a higher (72%, P = 0.03) paternal transmission of HLA-DRB1*1404 to affected offspring in comparison to unaffected offspring. HLA-DRB1*03 was also increased among JAT patients but did not reach statistical significance. CONCLUSION: These studies point towards an important role of immune modifying genes, such as HLA, in influencing susceptibility to juvenile-onset AITD.

Molecular diversity of the HLA-A*19 group of alleles in North Indians: possible oriental influence.

The present study aims to determine the genetic diversity of the HLA-A19 allelic family in the North Indian and Japanese populations. The HLA-A*19 group of alleles occurred at similar frequencies in North Indians and Japanese as in Caucasians. All the known serological splits of HLA-A19 were observed among the North Indians, i.e. A*33 (15.6%), A*32 (8.6%), A*31 (3.5%), A*30 (3%), A*29 (1.2%) and A*74 (0.77%), while only A*30 (0.7%), A*31 (17.6%) and A*33 (11.7%) were observed in the Japanese. High resolution analysis indicated that the A*29, A*30, A*31 and A*32 alleles were represented by only single subtypes among the North Indians while the HLA-A*33 group comprised two alleles, A*3301 (4.3%) and A*3303 (43.7%). All 15 of the HLA-A*33 positive samples from the Tamil population of South India were found to be A*3303. One novel subtype of A*33, A*3306 was also observed in the North Indian sample. Conversely, only one subtype each of A*30, A*31 and A*33 was encountered in the Japanese population, of which A*3101 and A*3303 were the most frequent (58.5% and 39%, respectively, among the HLA-A*19 group of alleles). All other subtypes of A19 were not found in the Japanese in the present study. The study suggests a significant amount of genetic admixture in the North Indian gene pool from other racial groups, with profound oriental influence.

Influence of HLA compatibility on renal graft survival using live unrelated & cadaver donors in India.

BACKGROUND & OBJECTIVES: Living unrelated donor (LURD) renal transplantation has shown a rising trend over the last 5 yr at our center following the passing of The Transplantation of Human Organs Act by the Government of India in 1994. In this paper, the results of LURD and cadaver (CAD) donor renal transplantation are compared. We have also looked into factors that have a bearing on graft survival such as the extent of HLA mismatch (MM), infections, acute rejections (AR), donor age and sex. METHODS: A total of 42 LURD and 25 CAD renal transplants performed between March 1994 and February 1999 has been included in the study. HLA typing, panel reactive antibody (PRA) screening and T and B cell cross match assay were performed by the complement dependent cytotoxicity (CDC) method for all patients. RESULTS: The graft survival rates were generally higher in the LURD category as compared to the CAD group and were significant at 6 month period (90 vs 56%, P = 0.002). A follow up of the patients up to 60 months revealed a matching effect since the 3, 4 allele MM group had better survival rates as compared to the 5, 6 MM group. Twenty six of the 67 recipients (39%) experienced episodes of acute rejection (AR). Patients with 3, 4 MM had fewer such episodes than those with 5, 6 allele MM (P < 0.05). Of the 32 deaths, 20 were those with a functional kidney, of which 15 were caused by severe infections. INTERPRETATION & CONCLUSION: Better HLA matching ensures fewer episodes of rejection and better long term graft survival in comparison to the poorly matched grafts. The graft survival for LURD recipients was appreciably higher than that of CAD recipients.

Common HLA-B8-DR3 haplotype in Northern India is different from that found in Europe.

The aim of this study was to determine whether a common diabetic haplotype, including human leukocyte antigen (HLA)-B8 and HLA-DR3, in Northern India is the same haplotype as the European HLA-B8-DR3 haplotype. DNA samples from Northern Indian subjects selected on the basis of HLA-B8 and HLA-DR3 were tested for microsatellite and single nucleotide polymorphism alleles throughout the major histocompatibility complex (MHC). It was found that the Indian samples represent a conserved haplotype in which all alleles were shared by Indian subjects with HLA-B8 and HLA-DR3, but were different to those that are characteristic of the European 8.1 ancestral haplotype. The Indian and European haplotypes share HLA-B*0801, HLA-DRB1*0301 and HLA-DQB1*02 but differ for subtypes of HLA-Cw*07 and HLA-DRB3 and all central MHC alleles tested. In contrast, Indian subjects selected on the basis of HLA-B58 ( 1-17) and HLA-DR3 shared the same alleles at other MHC loci as have been described in the common Chinese haplotype with HLA-B58/17 and HLA-DR3. A third haplotype, HLA-B50/21 and HLA-DR3, was also found to be highly conserved but shares little in common with the other two HLA-DR3-containing Indian haplotypes.

Molecular diversity of the HLA-B27 gene and its association with disease.

Abstract The human major histocompatibility complex (MHC) class I gene HLA-B27 bears a striking association with ankylosing spondylitis and related spondyloarthropathies. This association transcends all ethnic and geographical boundaries. The primary function of HLA-B27 as an MHC class I protein is to form a complex with ß2-microglobulin resulting in a structure that is capable of presenting short antigenic peptides for recognition by cytotoxic T lymphocytes. HLA-B27 represents a family of 23 closely related alleles (B (*) 2701-23) called subtypes of HLA-B27, most of which have evolved from B (*) 2705. Studies from different parts of the world reveal differences in the population distribution. HLA-B27 subtypes are characterized by nucleotide substitutions (mostly nonsynonymous) in exons 2 and 3 which encode α1 and α2 domains of the peptide binding groove respectively. Gene conversion, point mutation, genetic draft, and recombination events are various mechanisms leading to heterogeneity of HLA-B27 and its evolution. Clustering of differences in the C/F pockets of HLA-B27 influences the peptide binding. Thus variations in strength of disease association of various HLA-B27 subtypes may be due to differences in peptide interaction of HLA-B27 subtypes. Because the association between HLA-B27 and disease is not absolute, possible influence of other genes on disease susceptibility needs further investigation. In this regard, the role of several candidate genes that include non-B27 MHC genes, MHC-related genes, MHC genes involved in antigen processing and transplant, cytokine genes, and markers on other chromosomes may be important. Besides these significant developments, satisfactory answers to many unresolved issues are sought. Understanding the exact mechanism of the HLA-B27 and disease association is continuing to be a subject of many studies.

HLA-B27 alone rather than B27-related class I haplotypes contributes to ankylosing spondylitis susceptibility.

Characterization of non-B27 susceptibility genes will be required to know the pathogenesis of AS. The aim of this study was to examine whether ankylosing spondylitis (AS) susceptibility is controlled by B27 alone rather than B27 haplotypes and, whether other closely related class I loci, such as MICA and TNFA genes might play a role in AS. Three hundred eleven B27-positive samples from Caucasoid, Asian, and African populations were selected and genotypes were carried out by PCR/SSOP (HLA-B27 and HLA-C), PCR/SSP (MICA-TM polymorphism in the transmembrane region), PCR/SSCP (MICA alleles), and PCR-RFLP (TNF-alpha). Of these, 161 were AS patients, chosen in order to investigate the contribution of TNFA and MICA loci to AS in HLA-B27 positive individuals. Some findings can be concluded from the study: (a) No significant differences of TNF-alpha promoter alleles at position -308 and -238 (A/G) were found between AS patients and B27 matched alleles from healthy controls; (b) strong linkage disequilibrium was found between the B27 and the MICA alleles. The MICA-A4 was found to be in association with B*2705,02,03 and 08; MICA-A5 with B*2704 and B*2707 and MICA-A.5.1 with B*2706; (c) no significant differences of MICA alleles were found between AS and controls carrying the B27-associated alleles, and therefore no evidence is provided for an additional role of MICA gene in AS susceptibility; (d) there are a striking correlations between the structure of B27 extended haplotypes (from MICA region to HLA-C) and the ethnic distribution of these subtypes. The results of differential linkage disequilibrium with HLA-B27 subtypes suggest that B27 itself remains the primary gene for AS susceptibility, and TNFA and MICA are not involved in the pathogenesis of the disease.

Family studies and human leukocyte antigen class II typing in Indian probands with seizures in association with single small enhancing computed tomography lesions.

PURPOSE: To define the clinical features of the syndrome of seizures associated with single, small, enhancing computed tomography (CT) lesions (SSELs) in 235 Indian probands and seizure types among their family members. Human leukocyte antigen (HLA) class II genomic typing in randomly selected 41 probands was done to identify the role of hereditary factors in this syndrome. METHODS: The seizure types among 235 probands, their clinical outcome, and seizures in their family members were studied. Family data were collected on relatives of 212 additional probands with neurologic diseases other than epilepsy. HLA class II antigens were studied by using polymerase chain reaction (PCR) amplified DNA and sequence-specific oligonucleotide probe (PCR-SSOP) hybridization. RESULTS: The seizures in 86% were partial with or without generalization; 77% had fewer than five seizures before the first CT scan. Evanescent focal neurologic deficits after seizures were noted in 40%. Most patients (97%) were treated with a single antiepileptic drug (AED). Significant resolution of the CT scan lesion was noted within 6 months in 125 (53%) of 235 cases. Two thirds of patients had no seizures while taking a single AED, and an additional 18% had no seizures even after their AEDs were discontinued. Epilepsy among relatives of Indian probands having seizures in association with SSELs was more common as compared with relatives of probands with other neurologic diseases. A family history of seizures was noted in 21% probands, the ratio of affected first- to second-degree relatives was 4.3:1, and 60% of affected sibs had syndromic concordance with probands. There was a positive association of HLA-DRB1*13 (Pc = 0.036) with this syndrome. CONCLUSIONS: The syndrome of seizures in association with SSELs seems to be a benign localization-related epileptic syndrome. Our results of HLA studies point to an inherited susceptibility to an infective agent, which in most cases is of cysticercal etiology.

Immunogenetic analysis of Takayasu arteritis in Indian patients.

The distribution of HLA-A, B, C and DR antigens was determined in a cohort of 104 unrelated Indian patients with Takayasu arteritis (TA) belonging to the North Indian states of Punjab, Haryana, Uttar Pradesh and Delhi. The data was compared with healthy controls belonging to the same ethnic group. In addition, polymorphism in the MHC class I chain related A (MIC A) gene was studied in a group of 25 TA patients and 40 healthy controls. The data revealed a strong association of the disease with HLA-B5 (chi2=22.5, P<1 x 10(-6), RR=3.08) as well as its two common serological subtypes, B51 (chi2=20.5) and B52 (chi2=18.5). No particular association was observed with any of the five alleles of the MIC A gene, nor any linkage disequilibrium could be established with these alleles and those of HLA-B locus in this population. The observation suggest that HLA linked genes are definitely involved in the development of Takayasu arteritis and that the disease in Indian subjects is associated with HLA-B5 and its two serological subtypes, B51 as well as B52.

Seronegative spondyloarthropathies and HLA-B27 subtyes: a study in Asian Indians.

In this study, 60 HLA-B27+ve SSA patients and 17 healthy controls belonging to North India were analyzed to ascertain heterogeneity of the B27 molecule in this population. ID-IEF and PCR-SSOP technologies were used to analyze polymorphism in exon 2 and 3 of the HLA-B27 gene. Four different subtypes were encountered: B*2702,04,05 and 07. Other subtypes of B27 viz B*2701,03,06 and 08 were not encountered. B*2704 (common oriental subtype) and B*2705 (common Caucasian subtype) were the most common subtypes in the control and patient groups. B*2707 was less frequently encountered in both groups and B*2702 was found in only one AAU patient. B*2704 was the predominant subtype in the AS group (70.8%) compared to its frequency of 47% in healthy controls (RR = 2.73) while in the undiff SpA group, B*2705 occurred most frequently (73.1%, RR = 3.05). B27 subtypes segregated differently in males and females. 12 of the 17 male AS patients carried B*2704 as compared to 1 of 8 healthy males (X2 = 3.9, P < 0.05). On the other hand, in the undiff SpA, B*2705 was significantly raised in female patients (100%) as compared to healthy females (22.2%, X2 = 4.9, P < 0.05). Subtype distribution is indicative of racial admixture in the Asian Indian population.

HLA-B27 subtypes in Asian patients with ankylosing spondylitis. Evidence for new associations.

The aim of this study was to investigate the contribution of the different B27 subtypes to ankylosing spondylitis (AS) susceptibility. The polymerase chain reaction (PCR) in combination with the sequence-specific oligonucleotide probes (SSOs) was used to analyse the polymorphism in exon 2 and 3 of HLA-B27 in two Asian groups with different genetic HLA structures: Indian (I) and Thai (T) populations. The same number of AS patients (45) and healthy B27 positive donors (n = 17) from both populations were analysed in order to ascertain the B27 subtypes. Three different findings can be concluded from this study: 1) B*2707 has been found to be associated with AS in both populations. This association has not been previously reported in either ethnic group. 2) B*2704 is strongly associated with AS in the Thai patients (91% in AS vs. 47% in C; RR = 11.5; EF = 0.83). In contrast, B*2704 was found with similar frequency in Asian Indians AS patients and controls (41% in AS vs. 41% in C.). 3) B*2706 was found overrepresented in control populations and absent in AS patients (0% in AS vs. 47% in C.; pc < 10(-6)) showing the maximum value of protective fraction (PF = 1). The B*2706 negative association with AS has not been previously described in other ethnic groups and could indicate a protective effect of this subtype on AS susceptibility. The B*2706 allele has two changes relative to B*2704 at residue 114 (His to Asp) and 116 (Asp to Tyr) in the pockets D/E. The importance that these differences can play in the pathogenesis of AS are discussed.