Uma Kanga

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.

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.

Immunogenetics of autoimmune diseases in Asian Indians.

Abstract: The HLA class II molecules play a critical role in the processing and presentation of specific peptides derived from autoantigens of pancreatic beta cells or gluten for T cell scrutiny in IDDM and CD. In the present study, extended DR3‐positive haplotypes associated with autoimmunity in northern Indian patients have been reported. The haplotype A26‐B8‐DR3 was the most common autoimmunity‐favoring haplotype encountered among these patients. This association is, indeed, unique to Indian autoimmune patients, as it replaces the otherwise most commonly associated Caucasian haplotype A1‐B8‐DR3 (AH8.1) in this population. Further, CD patients revealed 100% association with DQB1*0201 along with DQA*0501 (97%) either in cis or trans configuration.

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 recipients 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.

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.

Genomic evaluation of HLA-DR3+ haplotypes associated with type 1 diabetes

We have defined three sets of HLA‐DR3+ haplotypes that provide maximum risk of type 1 disease development in Indians: (1) a diverse array of B8‐DR3 haplotypes, (2) A33‐B58‐DR3 haplotype, and (3) A2‐B50‐DR3 occurring most predominantly in this population. Further analysis has revealed extensive diversity in B8‐DR3 haplotypes, particularly at the HLA‐A locus, in contrast to the single fixed HLA‐A1‐B8‐DR3 haplotype (generally referred to as AH8.1) reported in Caucasians. However, the classical AH8.1 haplotype was rare and differed from the Caucasian counterpart at multiple loci. In our study, HLA‐A26‐B8‐DR3 (AH8.2) was the most common B8‐DR3 haplotype constituting >50% of the total B8‐DR3 haplotypes. Further, A2‐B8‐DR3 contributed the maximum risk (RR = 48.7) of type 1 diabetes, followed by A2‐B50‐DR3 (RR = 9.4), A33‐B58‐DR3 (RR = 6.6), A24‐B8‐DR3 (RR = 4.5), and A26‐B8‐DR3 (RR = 4.2). Despite several differences, the disease‐associated haplotypes in Indian and Caucasian populations share a frozen DR3‐DQ2 block, suggesting a common ancestor from which multiple haplotypes evolved independently.

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 β2-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.

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.

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.

Differential expression of HLA-G and ILT-2 receptor in human tuberculosis: Localized versus disseminated disease.

Human leukocyte antigen-G (HLA-G) is an anti-inflammatory and immunosuppressive molecule that can modulate immune cell activation. The role of HLA-G in tuberculosis, an immune-mediated and chronic bacterial disease remains to be elucidated. We investigated the expression profile of soluble and membrane bound HLA-G in pulmonary TB (PTB), TB pleural effusion (TB-PE, localized disease) and Miliary TB (disseminated form). The expression of HLA-G receptor, ILT-2 was also determined on the immune cells. We observed that the plasma sHLA-G levels were significantly increased in Miliary TB than in TB-PE patients. In contrast, immunophenotyping revealed that the percent frequency of CD3(+) T cells expressing HLA-G was significantly reduced in Miliary TB as compared to TB-PE, whereas frequency of CD14(+) monocytes expressing HLA-G was significantly higher in TB-PE patients. Strikingly in the TB-PE cases, comparison of disease site, i.e. pleural effusion with peripheral blood showed increased expression of both soluble and surface HLA-G, whereas ILT-2 expressing cells were reduced at the local disease site. Furthermore, we demonstrated that in TB-PE cases, HLA-G expression on CD3(+) T cells was influenced by broad spectrum MMP inhibitor. Thus, differential expression of HLA-G could potentially be a useful biomarker to distinguish different states of TB disease.