HLA-DQ associations with autoimmune disease

BIITE: A Tool to Determine HLA Class II Epitopes from T Cell ELISpot Data

Activation of CD4+ T cells requires the recognition of peptides that are presented by HLA class II molecules and can be assessed experimentally using the ELISpot assay. However, even given an individual's HLA class II genotype, identifying which class II molecule is responsible for a positive ELISpot response to a given peptide is not trivial. The two main difficulties are the number of HLA class II molecules that can potentially be formed in a single individual (3-14) and the lack of clear peptide binding motifs for class II molecules. Here, we present a Bayesian framework to interpret ELISpot data (BIITE: Bayesian Immunogenicity Inference Tool for ELISpot); specifically BIITE identifies which HLA-II:peptide combination(s) are immunogenic based on cohort ELISpot data. We apply BIITE to two ELISpot datasets and explore the expected performance using simulations. We show this method can reach high accuracies, depending on the cohort size and the success rate of the ELISpot assay within the cohort.

Immunogenetics of drug-induced skin blistering disorders. Part II: Synthesis

The overall immunopathogenesis relevant to a large series of disorders caused by a drug or its associated hyperimmune condition is discussed based upon examining the genetics of severe drug-induced bullous skin problems (sporadic idiosyncratic adverse events including Stevens–Johnson syndrome and Toxic epidermal necrolysis). New results from an exemplar study on shared precipitating and perpetuating inner causes with other related disease phenotypes including aphtous stomatitis, Behçets, erythema multiforme, Hashimoto’s thyroiditis, pemphigus, periodic fevers, Sweet’s syndrome and drug-induced multisystem hypersensitivity are presented. A call for a collaborative, wider demographic profiling and deeper immunotyping in suggested future work is made.

The anti-oxidant defence response in individuals with the indeterminate form of Chagas disease (American trypanosomiasis)

In previous studies in animal models, Trypanosoma cruzi-induced oxidative stress and damage have sometimes been controlled by the host's anti-oxidant defence responses. The role of the anti-oxidant defence responses, such as the activities of the anti-oxidant enzymes glutathione peroxidase (GPx) and superoxide dismutase (SOD), in protection against inflammation and damage have now been investigated in humans infected with T. cruzi. The subjects were 32 asymptomatic but seropositive individuals with the indeterminate form of Chagas disease, 18 symptomatic and seropositive patients with the chronic disease, and 50 seronegative and apparently healthy controls. The inflammatory process was explored using serum concentrations of tumour necrosis factor (TNF) and NO. The serum concentrations of GPx in the patients in the indeterminate phase of infection were similar to those in the controls but much higher than those in the chronic cases (P=0.001). The serum concentrations of SOD in the patients in the indeterminate phase of infection were not only significantly higher than those in the cases of chronic Chagas disease (P=0.0004) but also significantly higher than those in the controls (P<0.001). The seropositive subjects had significantly higher serum concentrations of TNF and NO than the controls (P<0.01 for each) and the cases of chronic Chagas disease had significantly higher serum concentrations of TNF and NO than the subjects with the indeterminate form of the disease (P<0.01 for each). It therefore appears that the host's anti-oxidant defence responses (at least in terms of elevated concentrations of SOD) may inhibit inflammation during the indeterminate phase of Chagas disease.

Human leucocyte antigen class II association in idiopathic bronchiectasis, a disease of chronic lung infection, implicates a role for adaptive immunity

The aetiology of idiopathic bronchiectasis, a lung disease where chronic inflammation and bacterial infection leads to progressive lung damage, is unknown. A possible role for natural killer cells has been highlighted previously. However, a role for adaptive immunity is suggested by the presence of CD4 and CD8 T cells in diseased lung tissue. Evidence of a human leucocyte antigen (HLA) class II disease association would further implicate a role for adaptive immunity. To establish if there is any HLA association, we analysed HLA-A, HLA-B, HLA-DQA1, HLA-DQB1 and HLA-DRB1 alleles in patients with idiopathic bronchiectasis and controls. Genomic DNA from 92 adults with idiopathic bronchiectasis and 101 healthy controls was analysed by polymerase chain reaction with sequence-specific primers. We found an increase in the prevalence of HLA-DRB1*01 DQA1*01/DQB1*05 genes in idiopathic bronchiectasis; that is, the HLA-DR1, DQ5 haplotype (odds ratio 2.19, 95% confidence interval 1.15-4.16, P = 0.0152) compared with control subjects. The association with HLA-DR1, DQ5 implicates a role for CD4 T cells restricted by these molecules in susceptibility to the progressive lung damage seen in this disease. This may operate either through influencing susceptibility to specific pathogens or to self-reactivity and requires further investigation.

HLA-DQA is associated with abdominal aortic aneurysms in the Belgian population

Chronic inflammation and autoimmunity likely contribute to the pathogenesis of abdominal aortic aneurysms (AAAs). The aim of this study was to investigate the role of autoimmunity in the etiology of AAAs using a genetic association study approach with human leukocyte antigen (HLA) polymorphisms (HLA-DQA1, -DQB1, -DRB1 and -DRB3-5 alleles) in 387 AAA cases and 426 controls. We observed an association with the HLA-DQA1 locus among Belgian males, and found a significant difference in the HLA-DQA1*0102 allele frequencies between AAA cases and controls. In conclusion, this study showed potential evidence that the HLA-DQA1 locus harbors a genetic risk factor for AAAs suggesting that autoimmunity plays a role in the pathogenesis of AAAs.

Evidence for association between the HLA-DQA locus and abdominal aortic aneurysms in the Belgian population: a case control study

BACKGROUND

Chronic inflammation and autoimmunity likely contribute to the pathogenesis of abdominal aortic aneurysms (AAAs). The aim of this study was to investigate the role of autoimmunity in the etiology of AAAs using a genetic association study approach with HLA polymorphisms.

METHODS

HLA-DQA1, -DQB1, -DRB1 and -DRB3-5 alleles were determined in 387 AAA cases (180 Belgian and 207 Canadian) and 426 controls (269 Belgian and 157 Canadian) by a PCR and single-strand oligonucleotide probe hybridization assay.

RESULTS

We observed a potential association with the HLA-DQA1 locus among Belgian males (empirical p = 0.027, asymptotic p = 0.071). Specifically, there was a significant difference in the HLA-DQA1*0102 allele frequencies between AAA cases (67/322 alleles, 20.8%) and controls (44/356 alleles, 12.4%) in Belgian males (empirical p = 0.019, asymptotic p = 0.003). In haplotype analyses, marginally significant association was found between AAA and haplotype HLA-DQA1-DRB1 (p = 0.049 with global score statistics and p = 0.002 with haplotype-specific score statistics).

CONCLUSION

This study showed potential evidence that the HLA-DQA1 locus harbors a genetic risk factor for AAAs suggesting that autoimmunity plays a role in the pathogenesis of AAAs.

T-cell apoptosis and differential human leucocyte antigen class II expression in human thymus

Relatively little is known of the details of human leucocyte antigen (HLA) expression and thymocyte selection in human thymus. In both humans and mice major histocompatibility complex (MHC) molecules have been described which show a highly restricted thymic expression. Such patterns may offer clues about cellular interactions in thymic selection because transgenic mice with MHC expression targeted to specific thymic sites show altered T-cell receptor (TCR) repertoire selection. We have analysed human thymic HLA class II expression, relating the expression pattern to sites of thymocyte apoptosis. While HLA-DQ is poorly expressed by most peripheral antigen-presenting cells (APC), thymus stains strongly for HLA-DQ as well as for HLA-DR. HLA-DM is abundant in medulla but weakly expressed by cortical cells. Class II expression in Hassall's corpuscles (HC) is unusual in several respects: we have previously shown them to be encircled by HLA-DO+ epithelial cells and here further demonstrate that HC are negative for HLA-DR and HLA-DP, but often positive for HLA-DQ and HLA-DM. Transcriptional control of HLA class II products at this site is thus unlike cells that have previously been studied. Apoptotic thymocytes are restricted to the cortex and the corticomedullary junction. However, a minority of apoptotic cells are visible in the medulla, these being found in the HLA-DQ positive HC. The apoptotic thymocytes in HC can be CD4+ single positive (SP), CD8+ SP or CD4+CD8+ double-positive (DP). This study thus shows that the HC within human thymic medulla are noteworthy both for their unusual hierarchy of HLA class II expression and because they are the only medullary site of thymocyte apoptosis. We propose that HC are a site at which mature thymocytes receive activation/tolerization signals from peptides reprocessed from apoptotic cells. The differential HLA transcriptional control at this site may indicate that specific T-cell subpopulations are affected.

HLA-DQA1 and -DQB1 genotyping by PCR-RFLP, heteroduplex and homoduplex analysis

PCR-RFLP typing methods for DQA1 and DQB1 in conjunction with the analysis of heteroduplex and homoduplex patterns have allowed a simple method for typing all of the major DQA1 and DQB1 alleles. This method has advantages over PCR amplification with sequence-specific primers (PCR-SSP), PCR hybridization with sequence-specific oligonucleotide probes (PCR-SSO) and other PCR-RFLP strategies for typing DQ alleles. The analysis of heteroduplex and homoduplex patterns can be used in conjunction with other PCR typing systems such as PCR-SSP as a confirmatory step with little additional work. In addition, a PCR-RFLP strategy was designed for resolving the DQB1*0602 and DQB1*0603 alleles, which involved the use of a primer containing a base mutation, creating a new restriction site which distinguished the two alleles. These techniques have enabled resolution of the major homozygous and heterozygous combinations of these DQA1 and DQB1 alleles. The PCR-RFLP technique does not require the large number of oligonucleotides that are necessary for both the PCR-SSP and PCR-SSO techniques and is thus both time and cost effective for infrequent or small numbers of samples.