Pathogenesis of autoimmune diseases associated with 8.1 ancestral haplotype: a genetically determined defect of C4 influences immunological parameters of healthy carriers of the haplotype

Low C4A copy numbers and higher HERV gene insertion contributes to increased risk of SLE, with absence of association with disease phenotype and disease activity

Low copy numbers (CNs) of C4 genes are associated with systemic autoimmune disorders and affects autoantibody diversity and disease subgroups. The primary objective of this study was to characterize diversity of complement (C4) and C4-Human Endogenous Retrovirus (HERV) gene copy numbers in SLE. We also sought to assess the association of C4 and C4-HERV CNs with serum complement levels, autoantibodies, disease phenotypes and activity. Finally, we checked the association of C4 and HERV CNs with specific HLA alleles. Genomic DNA from 70 SLE and 90 healthy controls of south Indian Tamil origin were included. Demographic, clinical and serological data was collected in a predetermined proforma. CNs of C4A and C4B genes and the frequency of insertion of 6.4kb HERV within C4 gene (C4AL, C4BL) was determined using droplet digital polymerase chain reaction (ddPCR). A four digit high resolution HLA genotyping was done using next generation sequencing. In our cohort, the total C4 gene copies ranged from 2 to 6. Compared to controls, presence of two or less copies of C4A gene was associated with SLE risk (p = 0.005; OR = 2.79; 95% CI = 1.29-6.22). Higher frequency of HERV insertion in C4A than in C4B increases such risk (p = 0.000; OR = 12.67; 95% CI = 2.80-115.3). AL-AL-AL-BS genotype was significantly higher in controls than SLE (9%vs1%, p = 0.04; OR = 0.15, 95% CI = 0.00-0.16). Distribution of HLA alleles was not different in SLE compared to controls as well as in SLE subjects with ≤ 2 copies and > 2 copies of C4A, but HLA allele distribution was diverse in subjects with C4B ≤ 2 copies and > 2 copies. Finally, there was no correlation between the C4 and the C4-HERV diversity and complement levels, autoantibodies, disease phenotypes and activity. In conclusion, our data show that, low C4A copy number and higher insertion of HERV-K in C4A increases the risk for SLE. C4 and C4-HERV CNs did not correlate with serum complements, autoantibodies, disease phenotypes and activity in SLE. Further validation in a larger homogenous SLE cohort is needed.

Clinical Status, Nutritional Behavior, and Lifestyle, and Determinants of Community Well-Being of Patients from the Perspective of Physicians: A Cross-Sectional Study of Young Older Adults, Nonagenarians, and Centenarians in Salerno and Province, Italy

Longevity is rightly considered one of the greatest achievements of modern society. Biomedical research has shown that aging is the major risk factor for many diseases, so to find the right answers to aging it is necessary to identify factors that can positively influence longevity. This study investigated the clinical status, nutritional behavior, lifestyle, and social and community determinants of the well-being of young older adults and nonagenarians/centenarians in Salerno and province through the judgment of their physicians. Data were collected through an online survey. Multivariate Poisson and logistic regression models were used to calculate significant predictors of the outcomes of interest. The interesting finding was that cardiovascular disease was a risk factor for young older adults, while it was a protective factor for nonagenarians/centenarians, meaning that as age increased, heart problems tended to decrease. Certain foods were found to be a significant protective factor for both young older adult and nonagenarian-centenarian patients. In addition, psychosomatic disorders were found to be determinant for the young older adults, while depression was a risk factor for the nonagenarians/centenarians because they were not always gratified by their long lives and often felt like a burden on the family. The protective significant variable among the determinants of community well-being for both young older adults and nonagenarians/centenarians was the retention of honorary achievement. Based on our results, we are able to support the hypothesis of a difference between the young older adults and the nonagenarians/centenarians in clinical status, nutritional behaviors, lifestyle, and determinants of community well-being. However, societies need more social and educational programs that are able to build "a new idea of old age" by improving and supporting the young older adults and the nonagenarians/centenarians, with the goal of intergenerational solidarity, well-being, and social inclusion, as well as preventive interventions on lifestyles and nutrition, which will allow us to provide a new key to understanding aging.

Distinctive clinical presentation and pathogenic specificities of anti-AK5 encephalitis

Limbic encephalitis (LE) with antibodies against adenylate kinase 5 (AK5) has been difficult to characterize because of its rarity. In this study, we identified 10 new cases and reviewed 16 previously reported patients, investigating clinical features, IgG subclasses, human leukocyte antigen (HLA), and CSF proteomic profiles. Patients with anti-AK5 LE were mostly men (20/26, 76.9%) of median age 66 years old (range 48-94). Predominant symptom was severe episodic amnesia in all patients, frequently associated with depression (17/25, 68.0%). Weight loss, asthenia, and anorexia were also highly characteristic, being present in 11/25 (44.0%) patients. Although epilepsy was always lacking at disease onset, seizures developed later in a subset of patients (4/25, 16.0%). All patients presented CSF abnormalities, such as pleocytosis (18/25, 72.0%), oligoclonal bands (18/25, 72.0%), and increased Tau (11/14, 78.6%). Temporal lobe hyper-intensities were almost always present at disease onset (23/26, 88.5%), evolving nearly invariably toward a severe atrophy in subsequent MRIs (17/19, 89.5%). This finding was in line with a poor response to immunotherapy, with only 5/25 (20.0%) patients responding. IgG1 was the predominant subclass, being the most frequently detected and the one with highest titres in nine CSF-serum paired samples. Temporal biopsy from one of our new cases showed massive lymphocytic infiltrates dominated by both CD4+ and CT8+ T-cells, intense granzyme B expression, and abundant macrophages/microglia. HLA analysis in 11 patients showed a striking association with HLA-B*08:01 (7/11, 63.6%; OR = 13.4, 95% CI [3.8-47.4]), C*07:01 (8/11, 72.7%; OR = 11.0, 95% CI [2.9-42.5]), DRB1*03:01 (8/11, 72.7%; OR = 14.4, 95% CI [3.7-55.7]), DQB1*02:01 (8/11, 72.7%; OR = 13.5, 95% CI [3.5-52.0]), and DQA1*05:01 (8/11, 72.7%; OR = 14.4, 95% CI [3.7-55.7]) alleles, which formed the extended haplotype B8-C7-DR3-DQ2 in 6/11 (54.5%) patients (OR = 16.5, 95% CI [4.8-57.1]). Finally, we compared the CSF proteomic profile of five anti-AK5 patients with that of 40 controls and 10 cases with other more common non-paraneoplastic LE (five with antibodies against leucine-rich glioma inactivated 1 and five against contactin-associated protein-like 2), as well as 10 cases with paraneoplastic neurological syndromes (five with antibodies against Yo and five against Ma2). These comparisons revealed, respectively, 31 and seven significantly up-regulated proteins in anti-AK5 LE, mapping to apoptosis pathways and innate/adaptive immune responses. These findings suggest that the clinical manifestations of anti-AK5 LE result from a distinct T-cell mediated pathogenesis, with major cytotoxicity-induced apoptosis leading to a prompt and aggressive neuronal loss, likely explaining the poor prognosis and response to immunotherapy.

Collagenous Colitis Is Associated With HLA Signature and Shares Genetic Risks With Other Immune-Mediated Diseases

BACKGROUND & AIMS

Collagenous colitis (CC) is an inflammatory bowel disorder with unknown etiopathogenesis involving HLA-related immune-mediated responses and environmental and genetic risk factors. We carried out an array-based genetic association study in a cohort of patients with CC and investigated the common genetic basis between CC and Crohn's disease (CD), ulcerative colitis (UC), and celiac disease.

METHODS

DNA from 804 CC formalin-fixed, paraffin-embedded tissue samples was genotyped with Illumina Immunochip. Matching genotype data on control samples and CD, UC, and celiac disease cases were provided by the respective consortia. A discovery association study followed by meta-analysis with an independent cohort, polygenic risk score calculation, and cross-phenotype analyses were performed. Enrichment of regulatory expression quantitative trait loci among the CC variants was assessed in hemopoietic and intestinal cells.

RESULTS

Three HLA alleles (HLA-B∗08:01, HLA-DRB1∗03:01, and HLA-DQB1∗02:01), related to the ancestral haplotype 8.1, were significantly associated with increased CC risk. We also identified an independent protective effect of HLA-DRB1∗04:01 on CC risk. Polygenic risk score quantifying the risk across multiple susceptibility loci was strongly associated with CC risk. An enrichment of expression quantitative trait loci was detected among the CC-susceptibility variants in various cell types. The cross-phenotype analysis identified a complex pattern of polygenic pleiotropy between CC and other immune-mediated diseases.

CONCLUSIONS

In this largest genetic study of CC to date with histologically confirmed diagnosis, we strongly implicated the HLA locus and proposed potential non-HLA mechanisms in disease pathogenesis. We also detected a shared genetic risk between CC, celiac disease, CD, and UC, which supports clinical observations of comorbidity.

Autoimmune diseases and 8.1 ancestral haplotype: An update

The aim of the present review is to provide an update of the current research into the pathogenesis of autoimmune diseases associated with 8.1 ancestral haplotype. This is a common Caucasoid haplotype carried by most people who type for HLA-B8, DR3. Numerous genetic studies reported that individuals with certain HLA alleles have a higher risk of specific autoimmune disorders than those without these alleles. However, much remains to be learned about the heritability of autoimmune conditions. Recently, progress and advances in the field of genome-wide-association studies have revolutionized the capacity to perform large, economically feasible, and statistically robust analyses of HLA within 8.1 ancestral haplotype, and understand its contribute to autoimmune events. In this paper, the characteristic features of this haplotype that might give rise to diverse autoimmune phenotypes are reviewed, focusing on the contribution of the HLA-DRB1 gene, the most polymorphic sequence within the HLA II region.

Multiallelic copy number variation in the complement component 4A (C4A) gene is associated with late-stage age-related macular degeneration (AMD)

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of vision loss in Western societies with a strong genetic component. Candidate gene studies as well as genome-wide association studies strongly implicated genetic variations in complement genes to be involved in disease risk. So far, no association of AMD with complement component 4 (C4) was reported probably due to the complex nature of the C4 locus on chromosome 6.

METHODS

We used multiplex ligation-dependent probe amplification (MLPA) to determine the copy number of the C4 gene as well as of both relevant isoforms, C4A and C4B, and assessed their association with AMD using logistic regression models.

RESULTS

Here, we report on the analysis of 2645 individuals (1536 probands and 1109 unaffected controls), across three different centers, for multiallelic copy number variation (CNV) at the C4 locus. We find strong statistical significance for association of increased copy number of C4A (OR 0.81 (0.73; 0.89);P = 4.4 × 10(-5)), with the effect most pronounced in individuals over 78 years (OR 0.67 (0.55; 0.81)) and females (OR 0.77 (0.68; 0.87)). Furthermore, this association is independent of known AMD-associated risk variants in the nearby CFB/C2 locus, particularly in females and in individuals over 78 years.

CONCLUSIONS

Our data strengthen the notion that complement dysregulation plays a crucial role in AMD etiology, an important finding for early intervention strategies and future therapeutics. In addition, for the first time, we provide evidence that multiallelic CNVs are associated with AMD pathology.

Clinical Role of Human Leukocyte Antigen in Health and Disease

Most of the genes in the major histocompatibility complex (MHC) region express high polymorphism that is fundamental for their function. The most important function of human leukocyte antigen (HLA) molecule is in the induction, regulation of immune responses and the selection of the T cell repertoire. A clinician's attention is normally drawn to a system only when it malfunctions. The HLA system is no exception in this regard, but in contrast to other systems, it also arouses interest when it functions well - too well, in fact. Population studies carried out over the last several decades have identified a long list of human diseases that are significantly more common among individuals that carry particular HLA alleles including inflammatory, autoimmune and malignant disorders. HLA-disease association is the name of this phenomenon, and the mechanism underlying is still a subject of hot debate. Social behaviours are affected by HLA genes and preference for HLA disparate mates may provide 'good genes' for an individual's offspring. Also, certain HLA genes may be associated with shorter life and others with longer lifespan, but the effects depend both on the genetic background and on the environmental conditions. The following is a general overview of the important functional aspects of HLA in health and diseases.

Association between Human Leukocyte Antigens (HLA-A, -B, and -DR) and end-stage renal disease in Kuwaiti patients awaiting transplantation

The number of patients with end stage renal disease (ESRD) is increasing considerably worldwide. Human Leukocyte Antigens (HLAs) are relevant for the expression of many immunological diseases and contribute to the development of different nephropathies. Therefore, we aimed from the present work to investigate the possible association between the frequency of HLA-A, -B, and -DR antigens and ESRD in Kuwaiti patients awaiting renal transplant. HLA-A, -B, and -DR typing was performed by complement-dependent cytotoxicity (CDC) method for 334 patients with ESRD awaiting renal transplantation and 191 healthy controls. The frequency of HLA-B8 antigen was significantly higher in ESRD patients (OR = 2.62, p = 0.001, pc = 0.038), and the frequency of HLA-A28, HLA-DR11 antigens was significantly higher in healthy controls (OR 0.42, p = 0.0001; pc = 0.0021, and OR = 0.44, p = 0.0007, pc = 0.01 respectively). While the HLA-B8 antigen may be a susceptibility risk factor for development of ESRD, the HLA-A28, and HLA-DR11 antigens may be protective against development of ESRD in Kuwaiti population.

Myasthenia Gravis: paradox versus paradigm in autoimmunity

Myasthenia Gravis (MG) is a paradigm of organ-specific autoimmune disease (AID). It is mediated by antibodies that target the neuromuscular junction. The purpose of this review is to place MG in the general context of autoimmunity, to summarize the common mechanisms between MG and other AIDs, and to describe the specific mechanisms of MG. We have chosen the most common organ-specific AIDs to compare with MG: type 1 diabetes mellitus (T1DM), autoimmune thyroid diseases (AITD), multiple sclerosis (MS), some systemic AIDs (systemic lupus erythematous (SLE), rheumatoid arthritis (RA), Sjogren's syndrome (SS)), as well as inflammatory diseases of the gut and liver (celiac disease (CeD), Crohn's disease (CD), and primary biliary cirrhosis (PBC)). Several features are similar between all AIDs, suggesting that common pathogenic mechanisms lead to their development. In this review, we address the predisposing factors (genetic, epigenetic, hormones, vitamin D, microbiota), the triggering components (infections, drugs) and their interactions with the immune system [1,2]. The dysregulation of the immune system is detailed and includes the role of B cells, Treg cells, Th17 and cytokines. We particularly focused on the role of TNF-α and interferon type I whose role in MG is very analogous to that in several other AIDS. The implication of AIRE, a key factor in central tolerance is also discussed. Finally, if MG is a prototype of AIDS, it has a clear specificity compared to the other AIDS, by the fact that the target organ, the muscle, is not the site of immune infiltration and B cell expansion, but exclusively that of antibody-mediated pathogenic mechanisms. By contrast, the thymus in the early onset subtype frequently undergoes tissue remodeling, resulting in the development of ectopic germinal centers surrounded by high endothelial venules (HEV), as observed in the target organs of many other AIDs.

Peripheral hypertrophic subepithelial corneal degeneration: characterization, treatment and association with human leucocyte antigen genes

PURPOSE

To evaluate the efficacy of keratectomy in treating irregular astigmatism caused by peripheral hypertrophic subepithelial corneal degeneration (PHSD) and to study the possible underlying immunological risk factors.

MATERIALS AND METHODS

Patients (14 eyes) with diagnosed PHSD were treated with superficial keratectomy with or without the assistance of phototherapeutic keratectomy (VisX S4; VisX Inc., Santa Ana, CA, USA). Thirteen patients were subjected to analysis of human leucocyte antigen (HLA) genes, complement C4 gene numbers and total plasma immunoglobulin levels. Immunological risk factors between patients and a control group comprising 150 individuals were compared.

RESULTS

The mean preoperative best spectacle corrected visual acuity (BCVA) improved from 0.16 ± 0.22 (LogMAR scale range 0-0.7) to 0.06 ± 0.13 (-0.1-0.4) (p < 0.01). The mean preoperative astigmatism decreased significantly from 3.8 ± 2.1 D (range 1.2-8.2) to 2.1 ± 1.4 (range 0.6-5.0, p = 0.02) based on corneal topography. The HLA-B*44 allele and the ancestral haplotype (AH) 8.1 were found significantly more often in PHSD patients than in controls (both p = 0.03). No differences in the C4 genes were found.

CONCLUSIONS

Astigmatism secondary to PHSD can be effectively treated with keratectomy. Peeling of the fibrotic tissue reduced astigmatism and improved visual performance. We suggest that HLA-B*44 allele and AH 8.1 haplotype are immunological factors predisposing to the development of PHSD. The consequent disruption/alteration of the limbal barrier may lead to corneal peripheral fibrous formation inducing astigmatism.

Tumor necrosis factor B (TNFB) genetic variants and its increased expression are associated with vitiligo susceptibility

Genetic polymorphisms in TNFB are involved in the regulation of its expression and are found to be associated with various autoimmune diseases. The aim of the present study was to determine whether TNFB +252A/G (rs909253) and exon 3 C/A (rs1041981) polymorphisms are associated with vitiligo susceptibility, and expression of TNFB and ICAM1 affects the disease onset and progression. We have earlier reported the role of TNFA in autoimmune pathogenesis of vitiligo, and we now show the involvement of TNFB in vitiligo pathogenesis. The two polymorphisms investigated in the TNFB were in strong linkage disequilibrium and significantly associated with vitiligo. TNFB and ICAM1 transcripts were significantly increased in patients compared to controls. Active vitiligo patients showed significant increase in TNFB transcripts compared to stable vitiligo. The genotype-phenotype analysis revealed that TNFB expression levels were higher in patients with GG and AA genotypes as compared to controls. Patients with the early age of onset and female patients showed higher TNFB and ICAM1 expression. Overall, our findings suggest that the increased TNFB transcript levels in vitiligo patients could result, at least in part, from variations at the genetic level which in turn leads to increased ICAM1 expression. For the first time, we show that TNFB +252A/G and exon 3 C/A polymorphisms are associated with vitiligo susceptibility and influence the TNFB and ICAM1 expression. Moreover, the study also emphasizes influence of TNFB and ICAM1 on the disease progression, onset and gender bias for developing vitiligo.

HLA associations and Löfgren's syndrome

Patients with sarcoidosis can be subgrouped according to organ engagement and clinical manifestations. One such subgroup is Löfgren's syndrome (LS), constituting a distinct group of sarcoidosis patients with typical clinical manifestations, separate genetic associations and an immune response that seems to differ from that of non-LS patients. In particular, LS patients have strong associations with HLA-DRB1 alleles, and the well-known association with HLA-DRB1*03 is particularly striking. This particular HLA-DRB1 allele is also a very strong marker within that particular group of patients for a prognostically favorable disease course. This article will mainly discuss genetic associations with LS, and the possible implications of such associations.

Gender and the regulation of longevity: implications for autoimmunity

For humans and other animals, gender has an influence not only on their physical attributes, but also on life span. In humans, females have a longer life span than males. The reasons for this are not entirely clear. The role of gender in the regulation of longevity may be linked to gender specific genetic differences, including the expression of sex hormone patterns and the changes in these patterns during an individual's lifetime. In addition, the effect of sex hormones on other physiologic responses to environmental influences on cellular stress and oxidative damage may play a role in longevity. Gender can impact many disease states, including autoimmune diseases, and the factors that affect the development of autoimmune diseases and the regulation of longevity may share common mechanistic pathways. Other factors that may play a role include telomere and telomerase related differences, caloric restriction and changes in mitochondrial DNA. Inflammatory and regulatory pathways such as insulin/IGF signaling and Target of Rapamycin (TOR) signaling may also play a role in longevity and aging-related diseases such as Alzheimer's. The role of gender differences in the regulation of these pathways or factors is not entirely clear. The role of X-chromosome inactivation in longevity has also yet to be fully elucidated.

HLA-DRB1 allele frequencies and C4 copy number variation in Finnish sarcoidosis patients and associations with disease prognosis

Sarcoidosis is a multiorgan immune-mediated disease of unknown etiology with varying clinical pictures. We studied 3 genes in the major histocompatibility complex region (HLA-DRB1 and complement C4A and C4B) in patients with resolved disease after a 2-year follow-up (n = 90) and in patients whose disease was still active at that time point (n = 98) and compared them with controls (n = 150). Our primary aim was to detect genetic differences between the patient groups. We observed that the susceptibility allele for sarcoidosis was HLA-DRB1*15:01 (p = 0.011; odds ratio [OR] = 1.67) and the protective allele was HLA-DRB1*01:01 (p = 0.001; OR = 0.43). HLA-DRB1*03:01 was associated with resolving disease when compared with the persistent group (p = 0.011; OR = 2.22). The probability of having resolving disease was even greater if the patient had HLA-DRB1*03:01 and did not have extrapulmonary lesions (p = 0.001; OR = 3.39). By evaluating amino acid variants of the HLA-DRB1 gene, we determined that specific amino acids in pockets 4, 7, and 9 were associated with the prognosis of sarcoidosis. Our results support the importance of HLA-DRB1 as a predisposing gene for sarcoidosis. Particularly, HLA-DRB1*03:01 and polymorphisms of DRB1 pocket residues were associated with a favorable prognosis. Thus, accurate categorization of disease phenotype and HLA-DRB1 sequencing offer a basis for disease course estimation of sarcoidosis.

Ancestral haplotype 8.1 and lung disease severity in European cystic fibrosis patients

BACKGROUND

The clinical course of cystic fibrosis (CF) lung disease varies between patients bearing identical CFTR mutations. This suggests that additional genetic modifiers may contribute to the pulmonary phenotype. The highly conserved ancestral haplotype 8.1 (8.1AH), carried by up to one quarter of Caucasians, comprises linked gene polymorphisms on chromosome 6 that play a key role in the inflammatory response: LTA +252A/G; TNF -308G/A, HSP70-2 +1267A/G and RAGE -429T/C. As inflammation is a key component inducing CF lung damage, we investigated whether the 8.1AH represents a lung function modifier in CF.

METHODS

We analyzed the lung function of 404 European CF patients from France (n=230), Germany (n=95) and UK (n=79). FEV(1) differences between 8.1AH carriers and non-carriers were calculated in each country and pooled using a random effects model.

RESULTS

The frequency of 8.1AH carriers was similar between French (22%), German (29%) and UK (27%) patients. We found that 8.1AH carriers had significantly lower FEV(1), adjusted for age classes and countries (P<0.04, mean FEV(1) difference -6.4% CI95% [-12.4%, -0.5%]). No difference was observed with respect to BMI Z-scores and chronic colonization with P. aeruginosa.

CONCLUSIONS

These findings support the concept that 8.1AH is an important genetic modifier of lung disease in CF. To conclude, multiple linked genes outside the CF locus might explain some of the variability in lung phenotype.

Genotypic diversity of complement component C4 does not predict kidney transplant outcome

Gene copy number of complement component C4, which varies among individuals, may determine the intrinsic strength of the classical complement pathway. Presuming a major role of complement as an effector in transplant rejection, we hypothesized that C4 genetic diversity may partially explain the variation in allograft outcomes. This retrospective study included 1969 deceased-donor kidney transplants randomly selected from the Collaborative Transplant Study DNA bank. We determined recipient and donor gene copy number of total C4, C4 isotypes (C4A and C4B), and C4 gene length variants (C4L and C4S) by quantitative real-time PCR analysis. Groups defined according to recipient C4 gene copy number (low, intermediate, and high) had similar 10-year allograft survival. Genotypic groups showed comparable rates of graft dysfunction, treatment for rejection, immunological graft loss, hospitalization for infection, malignant disease, and death. Similarly, separate analyses of C4A, C4B, C4L, and C4S; combined evaluation of donor and recipient C4 genotype; or analysis of recipients with higher risk for rejection did not reveal considerable outcome effects. In conclusion, we did not demonstrate that C4 gene copy number associates with transplant outcome, and we found no evidence that the resulting variation in the strength of classical complement activation influences susceptibility to rejection.

Association of immunoglobulin A deficiency and elevated thyrotropin-receptor autoantibodies in two Nordic countries

Immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency, with suggested association with various types of autoimmunity, including Graves' disease. This study investigated the association of IgAD with elevated thyrotropin-receptor autoantibodies (TRAb). IgA was measured in TRAb-seropositive individuals from both Iceland (N = 299] and Sweden (N = 841]. In addition, TRAb levels were evaluated in 43 Icelandic and 50 Swedish IgAD individuals using Medizym TRA immunoassay, and positive samples were re-evaluated using BRAHMS TRAK human RIA. The IgAD individuals were HLA-genotyped to determine the HLA-B, DR, and DQ alleles. None of the 299 Icelandic TRAb-seropositive individuals had IgAD, whereas, a high prevalence of IgAD (14/841 (1:60)) was observed in the Swedish cohort (p = 0.027). The prevalence of TRAb-seropositivity in IgAD individuals was, however, increased in both cohorts. The HLA-DQ6 allele was associated with TRAb-seronegativity within the Icelandic IgAD cohort (p = 0.037). The prevalence of IgAD in TRAb-seropositive individuals in Sweden is 10 times higher than expected in the general population. Furthermore, TRAb seropositivity is common among IgAD individuals, both in Iceland and Sweden, suggesting a predisposition toward Graves' disease. These findings underline the significant association of IgAD with autoimmunity and its possible association with certain HLA-DQ alleles.

Major histocompatibility complex class II transactivator gene polymorphism: associations with Löfgren's syndrome

The major histocompatibility complex (MHC) class II transactivator (MHC2TA) is known as a master regulator for expression of MHC class II molecules. In the present study, we investigated the influence on the risk for sarcoidosis of two variants of the MHC2TA gene, selected from previous association studies of inflammatory diseases. Seven hundred and twenty-eight sarcoidosis patients and 873 controls matched by ethnicity were included in the study. Patients were classified as with Löfgren's syndrome (or not) as subphenotypes. Individuals were genotyped for two single nucleotide polymorphisms (SNPs) of the MHC2TA gene, rs3087456 A/G and rs11074932 C/T, and were human leukocyte antigen (HLA)-DRB1-typed. After correction for multiple testing, our data showed a significant association with Löfgren's syndrome in allelic model for the rs3087456 SNP, which was not detected in non-Löfgren's patients. A similar trend was noted for the rs11074932 SNP. These risk factors were independent of HLA-DRB1*03, which is known to be associated with Löfgren's syndrome. The finding of a new genetic association between Löfgren's syndrome and MHC2TA gene polymorphisms, which seems independent of HLA-DRB1*03 and relates to the expression of MHC class II molecules, strongly supports the idea that Löfgren's syndrome is a separate disease entity.

The human Major Histocompatibility Complex as a paradigm in genomics research

Since its discovery more than 50 years ago, the human Major Histocompatibility Complex (MHC) on chromosome 6p21.3 has been at the forefront of human genetic research. Here, we review from a historical perspective the major advances in our understanding of the nature and consequences of genetic variation which have involved the MHC, as well as highlighting likely future directions. As a consequence of its particular genomic structure, its remarkable polymorphism and its early implication in numerous diseases, the MHC has been considered as a model region for genomics, being the first substantial region to be sequenced and establishing fundamental concepts of linkage disequilibrium, haplotypic structure and meiotic recombination. Recently, the MHC became the first genomic region to be entirely re-sequenced for common haplotypes, while studies mapping gene expression phenotypes across the genome have strongly implicated variation in the MHC. This review shows how the MHC continues to provide new insights and remains in the vanguard of contemporary research in human genomics.

HLA-B8, DR3: a new risk factor for graft failure after renal transplantation in patients with underlying immunoglobulin A nephropathy

BACKGROUND

The HLA-B8, DR3 haplotype has been associated with high immune reactivity. In this study, we have tested whether this haplotype has differential effect on graft survival in patients with IgAN compared with control patients.

METHODS

From the Eurotransplant Registry we analyzed graft survival of 1207 recipients with IgAN and 7935 control patients with non-glomerular diseases. Death-censored graft loss according to the HLA-B8, DR3 haplotype was calculated with Kaplan-Meier analysis and Cox-regression model was used to correct for various risk factors.

RESULTS

The frequency of the HLA-B8, DR3 haplotype was significantly lower in IgAN patients compared with controls (10.3% vs. 15.4%, p < 0.001). Ten-year graft survival was identical in the control group with and without the HLA-B8, DR3 haplotype (71.1% and 70.2%, respectively), but significantly worse in IgAN patients carrying the HLA-B8, DR3 haplotype compared with patients without it (52.5% vs. 69.1%, respectively, p = 0.009). The risk of graft loss was increased by 66% (HR 1.6, 95% CI 1.14, 2.29) in IgAN with the HLA-B8, DR3 haplotype and independent of well-known risk factors.

CONCLUSIONS

We have identified a new risk factor for graft loss unique to patients with IgAN. This finding emphasizes the exclusive immune characteristics of IgAN patients after transplantation.

Linkage analysis of the C4A/C4B copy number variation and polymorphisms of the adjacent steroid 21-hydroxylase gene in a healthy population

Genes encoding the steroid 21-hydroxylase (CYP21A2) and the complement component C4 proteins (C4A and C4B) are located in the MHC region in a strongly linked structure named RCCX module. Previous studies found that carriers of C4B gene deficiency (C4B*Q0) have higher risk for cardiovascular diseases. A potential explanation is that lacking the C4B gene may result in altered function of the neighboring CYP21A2 gene. Therefore we sequenced the CYP21A2 gene in 96 healthy individuals to identify polymorphisms and to characterize their linkage pattern. Fifty-three variations were detected including a new one which alters the TATA-box of the gene. Only three known mutations (V281L, Q318X and R479L) associated with congenital adrenal hyperplasia, were found in 7, 2 and 1 subjects, respectively. Linkage analysis revealed that some variations exhibit strong correlation with the C4 copy number polymorphism and constituents of the MHC III region. Rare alleles of three polymorphisms were identified as components of the 8.1 ancestral haplotype. Haplotyping and family study confirmed that the variant alleles of two intronic SNPs were constituents of haplotype blocks lacking the C4B gene. These results suggest that variations of CYP21A2 gene can be involved in disease associations of the 8.1 haplotype and the C4B*Q0 genotype.

Löfgren's syndrome: human leukocyte antigen strongly influences the disease course

RATIONALE

Sarcoidosis may consist of a number of distinct disease entities, one of which could be Löfgren's syndrome. Patients with Löfgren's syndrome have an acute onset of erythema nodosum (EN) and/or periarticular inflammation or arthritis of the ankles, with bilateral hilar lymphadenopathy (and in some cases parenchymal infiltrates) and usually fever. There is a known association between HLA-DRB1*03 and Löfgren's syndrome.

OBJECTIVES

To investigate whether human leukocyte antigen type influences clinical manifestations, including the disease course in Löfgren's syndrome.

METHODS

We clinically characterized and HLA-DRB1 typed 301 patients with Löfgren's syndrome. A total of 275 of the patients were followed for more than 2 years and classified as having a nonresolving or a resolving disease.

MEASUREMENTS AND MAIN RESULTS

Almost every DRB1*03-positive patient had a resolving disease within 2 years, and 49% of the DRB1*03-negative patients developed a nonresolving disease. Mucosal granulomas were identified significantly more often in DRB1*03-negative patients. Among DRB1*03-negative patients who were treated with oral steroids at disease onset, 80% developed a nonresolving disease.

CONCLUSIONS

Patients with Löfgren's syndrome have a different disease course depending on whether they are DRB1*03 positive or not. This observation has clinical implications, and by comparing DRB1*03-positive and DRB1*03-negative patients with Löfgren's syndrome, we can search for additional markers of importance for developing a resolving or a nonresolving disease, respectively.

Polymorphisms of TNF-alpha and LT-alpha genes in multiple myeloma

Allelic distribution of -308 G>A (TNF 1/2) polymorphism of the TNF-alpha, and the +252 A>G promoter polymorphism of the LT-alpha gene, the 1267 A>G polymorphism of the HSP70-2 gene as well as the -429 T>C promoter polymorphism of the RAGE gene were tested in 94 MM cases and 141 controls. Significantly less MM patients than controls carried the TNF2 allele (p=0.018) and the TNF2-LTA 252G haplotype (p=0.025). The difference was, however, restricted to the females, as well as the relatively young (<69 years) subjects. By contrast, we did not find differences with the other SNPs tested.

The 8.1 ancestral MHC haplotype is strongly associated with colorectal cancer risk

Many recent data indicate that some alleles encoded in the central major histocompatibility complex (MHC) region (Class III) of short arm of chromosome 6 may modify the risk of cancer development. Therefore we determined 4 single nucleotide polymorphisms (SNPs) of this region (TNF-alpha -308 G > A, RAGE -429 T > C, HSP70-2 -1267 A > G, LTA 252 A > G) in genomic DNA samples from 183 Hungarian patients with colorectal cancer and 141 age matched control subjects representing the Hungarian population of the same age and gender. No significant differences were found in either SNP tested. When, however, three- or four-locus haplotypes consisting of known constituents of the so-called 8.1 ancestral haplotype (8.1AH) were considered, marked differences were observed. Frequency of TNF-alpha -308A, RAGE -429C, HSP70-2 -1267G, LTA 252G (8.1AH) haplotype was significantly (p = 0.006) more frequent (19.1%) among patients than in the controls (7.7%). Age- and gender-adjusted ratio of the 8.1AH carriers vs. non-carriers to have colorectal cancer was 2.514 (1.130-5.594). This risk was higher in <or=67 years old subjects (4.073 (1.317-12.596)) and in females (3.771 (1.302-10.927). These findings-consistent with similar recent results with ovarian cancer-indicate that carriers of the 8.1AH, encoding for an altered immune response and known to be associated with alterations of several immune functions and autoimmune diseases have an increased risk for some cancer types. These findings may contribute to better understanding how the defense mechanisms against tumors could be enhanced/strengthened.

Genetic Control of Immune Response in Carriers of the 8.1 Ancestral Haplotype: Correlation with Levels of IgG Subclasses: Its Relevance in the Pathogenesis of Autoimmune Diseases

Ancestral haplotype (AH) 8.1(HLA-A1, Cw7, B8, TNFAB*a2b3, TNFN*S, C2*C, Bf*s, C4A*Q0, C4B*1, DRB1*0301, DRB3*0101, DQA1*0501, DQB1*0201) seems to be associated with susceptibility to autoimmune diseases. Different mechanisms are probably involved in increasing autoimmunity, such as unbalanced cytokine production and the lack of C4A protein. So AH 8.1 modifies immune response in many ways. In this study we demonstrate that IgG2 serum levels were significantly lower in 8.1 AH carriers than in 8.1 AH non-carriers. On the contrary, as regards IgG1, IgG3, IgG4 serum levels, no significant differences were observed between the two groups. In AH 8.1 carriers low IgG2 levels might take to slower clearance of the infectious agent and hence to a lasting presence of it. The persistence of infectious antigens could determine an increased production of autoantibodies with a higher risk of cross-reactions.

Immunogenetics, gender, and longevity

In this article we discuss relevant data on aging, longevity, and gender with particular focus on inflammation gene polymorphisms which could affect an individual's chance to reach the extreme limit of human life. The present review is not an extensive revision of the literature, but rather an expert opinion based on selected data from the authors' laboratories. In 2000-2005 in the more developed regions, the life expectancy at birth is 71.9 years for men (78.3 in Japan) and 79.3 years for women (86.3 in Japan). Indeed, gender accounts for important differences in the prevalence of a variety of age-related diseases. Considering people of far-advanced age, demographic data document a clear-cut prevalence of females compared to males, suggesting that sex-specific mortality rates follow different trajectories during aging. In Italy this female/male ratio is relatively lower (about 5/1; F/M ratios are usually 5-6:1 in other developed countries), but significant differences have been observed between Italian regions in the distribution of centenarians by gender--from two women per man in the South to more than eight in certain regions in the North. Thus, a complex interaction of environmental, historical, and genetic factors, differently characterizing the various parts of Italy, likely plays an important role in determining the gender-specific probability of achieving longevity. This can be due to gender-specific cultural and anthropological characteristics of Italian society in the last 100 years. Age-related immunoinflammatory factors increase during proinflammatory status, and the frequency of pro/anti-inflammatory gene variants also show gender differences. There is some suggestion that people genetically predisposed to weak inflammatory activity may be at reduced chance of developing coronary heart disease (CHD) and, therefore, may achieve longer lifespan if they avoid serious life-threatening infectious disease thoroughout life. Thus, the pathogen burden, by interacting with host genotype, could determine the type and intensity of the immune-inflammatory response responsible for both proinflammatory status and CHD. These findings point to a strong relationship between the genetics of inflammation, successful aging, and the control of cardiovascular disease, but seem to suggest that the evidence for men is much stronger. The importance of these studies lies in the fact that half of the population (males) lives approximately 10% shorter lives than the other half (females). Understanding the different strategies that men and women seem to follow to achieve longevity may help us to comprehend better the basic phenomenon of aging and allow us to search for safe ways to increase male lifespan.

Genetic Control of Immune Response in Carriers of Ancestral Haplotype 8.1: The Study of Chemotaxis

In all caucasian populations the association of an impressive number of autoimmune diseases with genes from the HLA-B8, DR3 haplotype that is part of the ancestral haplotype (AH) 8.1 HLA-A1, Cw7, B8, TNFAB*a2b3, TNFN*S, C2*C, Bf*s, C4A*Q0, C4B*1, DRB1*0301, DRB3*0101, DQA1*0501, DQB1*0201 has been reported by different research groups. This haplotype, which is more common in northern Europe, is also associated with a number of immune system dysfunctions in healthy subjects. Analyzing the data according to gender, some dysfunctions are observed in women but not in men, in agreement with the role of X-linked genes and/or estrogens in the development and progression of autoimmune diseases. It has been proposed that a small number of genes within the 8.1 AH modify immune responsiveness and hence affect multiple immunopathological diseases. In this article, we demonstrate that neutrophil chemotaxis is significantly decreased in carriers of this AH, suggesting that this impairment may also be related to the increased occurrence of autoimmune diseases in these individuals.

Demonstration of high prevalence of SS-A antibodies in a general population: association with HLA-DR and enterovirus antibodies

Autoantibodies are helpful markers for diagnosing autoimmune diseases and there is a link between HLA-DR3 and the prevalence of SS-A antibodies in clinical groups. We aimed to study this association at the level of general adult population and to verify whether these antibodies are more common in persons with antibodies against enteroviruses as possible associates of Sjögren syndrome. The studied material included sera from 200 persons, randomly selected from a general population sample. The IgG type of SS-A/SS-B autoantibodies were measured by nuclear immunoblot, developed by us, and the results were compared to other results obtained by anti-SS-A immunoblot and ELISA. Enterovirus antibodies were detected by ELISA using common enterovirus antigenic peptide KEVPALTAVETGAT. Altogether 33 out of 200 sera showed SS-A and/or SS-B bands in immunoblot, including all seven ANA Profile 3 (Euroimmune) positive sera. One of the persons positive in these two tests showed also positive reaction on anti-SS-A ELISA (Euroimmune). None of the antibody-positive persons had Sjögren's syndrome or other rheumatic disease. Among 82 HLA typed persons, selected at random, the HLA-DRB1*03 and HLA-DRB1*11 allele carriers included significantly more persons with SS-A antibodies than the non-carries (p = 0.008). Antibodies against enterovirus peptide were present more frequently in persons with SS-A autoantibodies than in age- and sex-matched controls (p = 0.009). Summing up, our study showed that the prevalence of SS-A/SS-B antibodies in a general random population might be higher than thought previously being detected in up to 16.5% of persons including a significant number of those with HLA-DR3 or/and DR11 alleles and with antibodies against enteroviruses. Whether all these persons have the risk of developing rheumatic diseases should be evaluated by follow up studies.

The HLA 8.1 ancestral haplotype is strongly linked to the C allele of -429T>C promoter polymorphism of receptor of the advanced glycation endproduct (RAGE) gene. Haplotype-independent association of the -429C allele with high hemoglobinA1C levels in diabetic patients

Previously we reported on strong linkage disequilibrium (LD) between the mono-S-C4B-RCCX module (mono-S) and the TNF2 allele (both known constituents of the 8.1 ancestral haplotype (8.1 AH)) in two Caucasian populations. The gene for the receptor of advanced glycation endproducts (RAGE) is encoded between the RCCX module and the HLA class II genes in the central MHC region. In order to assess the relationship between the promoter polymorphisms of the RAGE gene and the 8.1 AH, we performed a family study in eight informative families affected with type 1 diabetes mellitus; haplotypes of a RAGE promoter SNP (-429T>C) with the HLA-DQ2, -DR-3(17) and TNF2 alleles, as well as the mono-S genotype were determined. A similar analysis was performed in 82 unrelated patients with type 1 diabetes mellitus, and in unrelated healthy individuals of three different Caucasian populations (Hungarians, Ohioian females, Icelandics). In the diabetic patients clinical correlations were also investigated. Out of the 32 paternal and maternal chromosome 6 from the eight families, 15 different MHC haplotypes were found. Haplotypes containing at least three of the known constituents of the 8.1 AH (HLA-DQ2, -DR17, mono-S, TNF2) were always linked to the RAGE -429C allele. The RAGE -429C allele exhibited highly significant (p<0.0001) LD coefficients to known constituents of the 8.1 AH both in healthy persons and patients with type 1 diabetes. In the group of patients with diabetes we found significantly (p=0.013) higher maximal hemoglobinA1C concentration in the carriers of the RAGE -429C allele, this trait, however was not linked to the 8.1 AH. Our present findings indicate that the RAGE -429C allele can be considered as a candidate member of the 8.1 AH. The results also reveal a spectrum of recombinant MHC haplotypes in addition to the conserved ancestral haplotypes.

Major histocompatibility complex and sporadic Alzheimer's disease: a critical reappraisal

Epidemiological data suggest that some genetic determinants of Alzheimer's disease (AD) might reside in those polymorphisms for the immune system genes that regulate immune inflammatory responses, such as the major histocompatibility complex (MHC). Therefore, MHC polymorphisms have been the focus of a large number of AD association studies. Class Ia, Ib (hemochromatosis gene (HFE)), class II and class III (complement, tumour necrosis factor and heat shock proteins) alleles have been studied. Nearly every positive result has been followed by several studies that have failed to replicate it or that have contradicted it. Several factors, including methodological biases, might explain these discordant results. However, the discordant results obtained with the same alleles in the various populations might also indicate linkage with another nearby locus, different in the diverse populations. In fact, the non-random assortment of alleles at neighbouring loci, i.e. ancestral haplotypes (AH), has been claimed to be maintained as the result of directional selection, i.e. molecular cooperation during the immune response. Thus, AH studies might contribute to explaining why discordant results are obtained with the same alleles in different populations. Hence, it has been suggested that the overall chance of a subject to develop AD might be profoundly affected by a 'susceptibility profile' reflecting the combined influence of inheriting multiple high-risk alleles. Discordant results may be due to other genetic factors not determined in these MHC studies and multivariate analysis in large patient cohorts considering both MHC and non-MHC genes are therefore necessary.