Genetics of autoimmune myasthenia gravis: The multifaceted contribution of the HLA complex

The novel HLA-C*03 allele, HLA-C*03:597, identified in a Chinese patient

HLA-C*03:597 differs from HLA-C*03:03:01:01 by a single non-synonymous nucleotide substitution in exon 5 (922 A>G).

Identification of LINC00173 in Myasthenia Gravis by Integration Analysis of Aberrantly Methylated- Differentially Expressed Genes and ceRNA Networks

Myasthenia gravis (MG) is an autoimmune disease associated with autoantibody production that leads to skeletal muscle weakness. The molecular mechanisms underlying MG are not fully understood. We analyzed the gene expression profile (GSE85452) and methylation profile (GSE85647) of MG samples from the GEO database to identify aberrantly methylated-differentially expressed genes. By integrating the datasets, we identified 143 hypermethylation-low expression genes and 91 hypomethylation-high expression genes. Then we constructed PPI network and ceRNA networks by these genes. Phosphatase and tensin homolog (PTEN) and Abelson tyrosine-protein kinase (ABL)1 were critical genes in both PPI networks and ceRNA networks. And potential MG associated lncRNAs were selected by comprehensive analysis of the critical genes and ceRNA networks. In the hypermethylation-low expression genes associated ceRNA network, sirtuin (SIRT)1 was the most important gene and the lncRNA HLA complex (HC) P5 had the highest connection degree. Meanwhile, PTEN was the most important gene and the lncRNA LINC00173 had the highest connection degree in the hypomethylation-high expression genes associated ceRNA network. LINC00173 was validated to be upregulated in MG patients by qRT-PCR (P = 0.005), which indicated LINC00173 might be a potential biomarker for MG. These results provide a basis for future studies on the molecular pathogenesis of MG.

NKT and NKT-like Cells in Autoimmune Neuroinflammatory Diseases-Multiple Sclerosis, Myasthenia Gravis and Guillain-Barre Syndrome

NKT cells comprise three subsets—type I (invariant, iNKT), type II, and NKT-like cells, of which iNKT cells are the most studied subset. They are capable of rapid cytokine production after the initial stimulus, thus they may be important for polarisation of Th cells. Due to this, they may be an important cell subset in autoimmune diseases. In the current review, we are summarising results of NKT-oriented studies in major neurological autoimmune diseases—multiple sclerosis, myasthenia gravis, and Guillain-Barre syndrome and their corresponding animal models.

HLA typing using next-generation sequencing for Chinese juvenile- and adult-onset myasthenia gravis patients

To compare HLA typing between juvenile- and adult-onset myasthenia gravis (MG), we enrolled 101 children (age ≤12 years) and 168 adults (age ≥20 years) with MG. We excluded patients with histories of thymoma, thyroid disease, or other autoimmune disease. We selected 41 seronegative juvenile-onset patients with ocular symptoms only, and 41 seropositive adult-onset patients with generalized symptoms. We used next-generation sequencing for typing and analysis of HLA genes (Loci: A, B, C, DPA1, DPB1, DQA1, DQB1 and DRB1). Haplotypes HLA-A∗02:07:01-B∗46:01:01-C∗01:02:01-DQA1∗01:01:01-DQB1∗03:03:02-DRB1∗09:01:02, HLA-A∗11:01:01, HLA-A∗24:02:01, and HLA-DPA1∗02:02:02 were found to be related to juvenile-onset MG and HLA-A∗01:01:01, HLA-A∗02:03:01, HLA-C∗03:04:01, and HLA-DQB1∗06:02:01 to adult-onset MG. Therefore, our findings suggested that HLA typing might determine the heterogeneity between AChR-Ab negative juvenile-onset and AChR-Ab positive adult-onset Chinese MG patients.

IFNA-AS1 regulates CD4+ T cell activation in myasthenia gravis though HLA-DRB1

Abnormal CD4⁺T cell activation is known to play roles in the pathogenesis of myasthenia gravis (MG). However, little is known about the mechanisms underlying the roles of lncRNAs in regulating CD4⁺ T cell. In this study, we discovered that the lncRNA IFNG-AS1 is abnormally expressed in MG patients associated with quantitative myasthenia gravis (QMG) and the positive anti-AchR Ab levels patients. IFNG-AS1 influenced Th1/Treg cell proliferation and regulated the expression levels of their transcription factors in an experimental autoimmune myasthenia gravis (EAMG)model. IFNG-AS1 could reduce the expression of HLA-DRB and HLA-DOB and they had a negative correlation in MG. Furthermore IFNG-AS1 influenced the expression levels of CD40L and CD4⁺ T cells activation in MG patient partly depend on effecting the HLA-DRB1 expression. It suggests that IFNG-AS1 may be involved in CD4⁺T cell-mediated immune responses in MG.

Association of HLA class II (DRB1, DQA1, DQB1) alleles and haplotypes with myasthenia gravis and its subgroups in the Iranian population

Heterogenic pattern of HLA associations with myasthenia gravis (MG) among different ethnicities and also among different MG subgroups has been the subject of debate in large series of many studies. One hundred and sixty Iranian MG patients were investigated for HLA class II (DRB1, DQA1, DQB1) associations compared to two hundred healthy controls from the same ethnic population. DRB1*11 DQA1*0501 DQB1*0301 haplotype was found to be protective for total (ocular plus generalized) MG (Pc=0.005, OR=0.49) and generalized MG (Pc=0.008, OR=0.49). DRB1*04 DQA1*0301 DQB1*0302 haplotype (Pc=0.03, OR=2.25) was predisposing for anti-acetylcholine receptor (AChR) antibody-positive MG, while DRB1*16 DQA1*0102 DQB1*05 (Pc=0.013, OR=4.28) was predisposing for anti-muscle specific tyrosine kinase (MuSK) antibody-positive MG. There was also a trend of positive association for DRB1*14 DQA1*0104 DQB1*05 haplotype with MuSK-positive MG (Pc=0.054, OR=3.97). Among other MG subgroups and with less significance, DRB1*0101 DQA1*0101 DQB1*05 haplotype (P=0.016, OR=3.68) had positive association with pure ocular MG, and DRB1*03 DQA1*0501 DQB1*0201 haplotype (P=0.024) had negative association with thymomatous MG. This study highlights the importance of appropriate MG subgrouping according to clinical and paraclinical characteristics in HLA studies among MG patients.

Myasthenia gravis: a comprehensive review of immune dysregulation and etiological mechanisms

Autoimmune myasthenia gravis (MG) is characterized by muscle weakness caused by antibodies directed against proteins of the neuromuscular junction. The main antigenic target is the acetylcholine receptor (AChR), but the muscle Specific Kinase (MuSK) and the low-density lipoprotein receptor-related protein (LRP4) are also targets. This review summarizes the clinical and biological data available for different subgroups of patients, who are classified according to antigenic target, age of onset, and observed thymic abnormalities, such as follicular hyperplasia or thymoma. Here, we analyze in detail the role of the thymus in the physiopathology of MG and propose an explanation for the development of the thymic follicular hyperplasia that is commonly observed in young female patients with anti-AChR antibodies. The influence of the pro-inflammatory environment is discussed, particularly the role of TNF-α and Th17-related cytokines, which could explain the escape of thymic T cells from regulation and the chronic inflammation in the MG thymus. Together with this immune dysregulation, active angiogenic processes and the upregulation of chemokines could promote thymic follicular hyperplasia. MG is a multifactorial disease, and we review the etiological mechanisms that could lead to its onset. Recent global genetic analyses have highlighted potential susceptibility genes. In addition, miRNAs, which play a crucial role in immune function, have been implicated in MG by recent studies. We also discuss the role of sex hormones and the influence of environmental factors, such as the viral hypothesis. This hypothesis is supported by reports that type I interferon and molecules mimicking viral infection can induce thymic changes similar to those observed in MG patients with anti-AChR antibodies.

Prognostic factors and health-related quality of life in ocular Myasthenia Gravis (OMG)

We evaluate the factors predictive of prognosis in 91 Caucasian patients affected by ocular myasthenia gravis (OMG), followed at our Institution during an observational time, ranging from 12 to 240 months. The Myasthenia Gravis Foundation of America (MGFA) clinical classification was used to grade the disease severity. We considered as outcome measures the variation in two subscores, ocular (O-QMG) and nonocular (NO-QMG); the last one reflected bulbar, neck, extremity functions. None of the independent variables evaluated for association with the outcome, as age of onset, type of therapy, length of interval between first and last examinations, and presence of antibodies to acetylcholine receptors (AChR-Abs) significantly affected the evolution of O-QMG and of NO-QMG. Health-related quality of life (HRQol) was assessed in 63 patients. Variations of diplopia or ptosis did not affect significantly physical (PCS) or mental composite subscores (MCS) of the Short-Form Health Survey (SF-36). Human leukocyte antigen (HLA) genotyping was studied to explore whether HLA class I and II allelic distribution differed among MG patients and controls. None of the studied HLA alleles significantly differed between OMG patients and controls. Similarly, none of the alleles with frequencies higher than 15% either in OMG patients or in controls was significantly associated, after Bonferroni correction, with the presence or absence of anti-AChR-Abs in serum.

Antibodies against low-density lipoprotein receptor-related protein 4 induce myasthenia gravis

Myasthenia gravis (MG) is the most common disorder affecting the neuromuscular junction (NMJ). MG is frequently caused by autoantibodies against acetylcholine receptor (AChR) and a kinase critical for NMJ formation, MuSK; however, a proportion of MG patients are double-negative for anti-AChR and anti-MuSK antibodies. Recent studies in these subjects have identified autoantibodies against low-density lipoprotein receptor-related protein 4 (LRP4), an agrin receptor also critical for NMJ formation. LRP4 autoantibodies have not previously been implicated in MG pathogenesis. Here we demonstrate that mice immunized with the extracellular domain of LRP4 generated anti-LRP4 antibodies and exhibited MG-associated symptoms, including muscle weakness, reduced compound muscle action potentials (CMAPs), and compromised neuromuscular transmission. Additionally, fragmented and distorted NMJs were evident at both the light microscopic and electron microscopic levels. We found that anti-LRP4 sera decreased cell surface LRP4 levels, inhibited agrin-induced MuSK activation and AChR clustering, and activated complements, revealing potential pathophysiological mechanisms. To further confirm the pathogenicity of LRP4 antibodies, we transferred IgGs purified from LRP4-immunized rabbits into naive mice and found that they exhibited MG-like symptoms, including reduced CMAP and impaired neuromuscular transmission. Together, these data demonstrate that LRP4 autoantibodies induce MG and that LRP4 contributes to NMJ maintenance in adulthood.

No association of the HLA-DQ alleles with myasthenia gravis in Cuban patients

Myasthenia gravis (MG) is a neuromuscular disorder characterized by fatigability and weakness of striated muscles. Its association with HLA molecules is well known and varies depending on age, sex and the ethnicity of the patients. A case-control study was performed in 61 Cuban patients and 81 controls using polymerase chain reaction and sequence-specific primers of the HLA-DQA1/B1 alleles. The distribution of the HLA-DQ alleles individually and in a simple haplotype between patients and controls shows no statistically significance differences. This result could be due to the heterogeneity and ethnic admixture existing in Cuban population. These findings indicate that the association between a disease and a particular genetic region cannot be explained merely by similarities in the genetic background but involve environmental and immunological factors.

The genetics of multiple sclerosis: an up-to-date review

Multiple sclerosis (MS) is a prevalent inflammatory disease of the central nervous system that often leads to disability in young adults. Treatment options are limited and often only partly effective. The disease is likely caused by a complex interaction between multiple genes and environmental factors, leading to inflammatory-mediated central nervous system deterioration. A series of genomic studies have confirmed a central role for the immune system in the development of MS, including genetic association studies that have now dramatically expanded the roster of MS susceptibility genes beyond the longstanding human leukocyte antigen (HLA) association in MS first identified nearly 40 years ago. Advances in technology together with novel models for collaboration across research groups have enabled the discovery of more than 50 non-HLA genetic risk factors associated with MS. However, with a large proportion of the disease heritability still unaccounted for, current studies are now geared towards identification of causal alleles, associated pathways, epigenetic mechanisms, and gene-environment interactions. This article reviews recent efforts in addressing the genetics of MS and the challenges posed by an ever increasing amount of analyzable data, which is spearheading development of novel statistical methods necessary to cope with such complexity.

Association of HLA-DQB1∗05:02 and DRB1∗16 Alleles with Late-Onset, Nonthymomatous, AChR-Ab-Positive Myasthenia Gravis

An association of several HLA alleles with myasthenia gravis (MG) has been reported. Aim of this work was to analyze the HLA allele profile in a survey of 76 unselected Italian MG patients and in a subgroup characterized by disease onset after the age of 50 years, absence of thymoma, and presence of antiacetylcholine receptor antibodies. We defined this subgroup by the acronym LOAb. Typing was performed at low resolution for HLA-A, -B, and -DRB1 loci with sequence-specific oligonucleotide probe (PCR-SSO); at high resolution for HLA-DQB1 locus by PCR with sequence-specific primers (PCR-SSPS). HLA allele frequencies were compared with 100 healthy controls. No correlation was observed between MG and the studied HLA class I alleles. On the contrary, a strong positive association was found for the HLA class II alleles DQB1∗05:02 (P(c) = 0.00768) and DRB1∗16 (P(c) = 0.0211) in the LOAb subgroup (n = 27) of MG patients. Association between DQB1∗05:02 and some subtypes of MG has been previously reported but not in patients with the LOAb characteristics. Therefore, the HLA allele DQB1∗05:02 might be considered as a susceptibility marker for LOAb among Italians.

The genetics of multiple sclerosis: an up-to-date review

Multiple sclerosis (MS) is a prevalent inflammatory disease of the central nervous system that often leads to disability in young adults. Treatment options are limited and often only partly effective. The disease is likely caused by a complex interaction between multiple genes and environmental factors, leading to inflammatory-mediated central nervous system deterioration. A series of genomic studies have confirmed a central role for the immune system in the development of MS, including genetic association studies that have now dramatically expanded the roster of MS susceptibility genes beyond the longstanding human leukocyte antigen (HLA) association in MS first identified nearly 40 years ago. Advances in technology together with novel models for collaboration across research groups have enabled the discovery of more than 50 non-HLA genetic risk factors associated with MS. However, with a large proportion of the disease heritability still unaccounted for, current studies are now geared towards identification of causal alleles, associated pathways, epigenetic mechanisms, and gene-environment interactions. This article reviews recent efforts in addressing the genetics of MS and the challenges posed by an ever increasing amount of analyzable data, which is spearheading development of novel statistical methods necessary to cope with such complexity.

Expanded dog leukocyte antigen (DLA) single nucleotide polymorphism (SNP) genotyping reveals spurious class II associations

The dog leukocyte antigen (DLA) system contains many of the functional genes of the immune system, thereby making it a candidate region for involvement in immune-mediated disorders. A number of studies have identified associations between specific DLA class II haplotypes and canine immune hemolytic anemia, thyroiditis, immune polyarthritis, type I diabetes mellitus, hypoadrenocorticism, systemic lupus erythematosus-related disease complex, necrotizing meningoencephalitis (NME) and anal furunculosis. These studies have relied on sequencing approximately 300 bases of exon 2 of each of the DLA class II genes: DLA-DRB1, DLA-DQA1 and DLA-DQB1. In the present study, an association (odds ratio=4.29) was identified by this method between Weimaraner dogs with hypertrophic osteodystrophy (HOD) and DLA-DRB1∗01501. To fine map the association with HOD, a genotyping assay of 126 coding single nucleotide polymorphisms (SNPs) from across the entire DLA, spanning a region of 2.5 Mb (3,320,000-5,830,000) on CFA12, was developed and tested on Weimaraners with HOD, as well as two additional breeds with diseases associated with DLA class II: Nova Scotia duck tolling retrievers with hypoadrenocorticism and Pug dogs with NME. No significant associations were found between Weimaraners with HOD or Nova Scotia duck tolling retrievers with hypoadrenocorticism and SNPs spanning the DLA region. In contrast, significant associations were found with NME in Pug dogs, although the associated region extended beyond the class II genes. By including a larger number of genes from a larger genomic region, a SNP genotyping assay was generated that provides coverage of the extended DLA region and may be useful in identifying and fine mapping DLA associations in dogs.

Serum protein profiles in myasthenia gravis

BACKGROUND

The diagnosis of myasthenia gravis (MG) remains challenging. We performed a proteome-wide search for potential serum protein diagnostic markers for MG using surface-enhanced laser desorption/ionization (SELDI) time-of-flight mass spectrometry (TOFMS).

METHODS

Proteomic spectra from 80 MG patients and 80 healthy individuals were generated by SELDI. Samples from 56 MG patients and 56 healthy individuals in the training set were analyzed to set up the decision tree. Samples from 24 MG patients and 24 healthy individuals were used for cross-validation testing.

RESULTS

The SELDI TOFMS analysis generated 101 peaks, representing differentially expressed proteins between 1000 and 20000 Da. Among them, 9 peaks were down-regulated and 30 others were up-regulated in the MG sera compared with the controls. The decision tree used the peak at M4168.94 Da and M1122.57 Da as splitters in the classification process. In the training set, 112 samples were classified as MG or control group, with a sensitivity of 100% and specificity of 89.3%; the 10-fold cross-validated analysis identified the optimal decision tree with the lowest relative cross-validated cost of 0.080. In the test set, the decision tree generated was able to identify 20 of 24 MG patients and 21 of 24 healthy individuals with a sensitivity of 83.3% and a specificity of 87.5%.

CONCLUSIONS

SELDI TOFMS is a useful tool for the detection and identification of potential serum biomarkers that can diagnose MG with high sensitivity and specificity.

Evidence for the specificity for platelet HPA-1a alloepitope and the presenting HLA-DR52a of diverse antigen-specific helper T cell clones from alloimmunized mothers

Maternal alloantibodies against the human platelet Ag (HPA)-1a allotype of the platelet beta(3) integrin GpIIb/IIIa can cause severe fetal or neonatal hemorrhage. Almost all anti-HPA-1a-immune mothers are homozygous for HPA-1b and carry HLA-DR52a (DRB3*0101). The single Pro(33) -->Leu substitution (HPA-1b-->HPA-1a) was previously predicted to create a binding motif for HLA-DR52a that can lead to alloimmunization. We have isolated six CD4(+) T cell clones from three such mothers, which all respond to intact HPA-1a(+), but not HPA-1b(+), platelets. We used them to define the "core" and "anchor" residues of this natural T cell epitope. Molecular modeling based on a recently published crystal structure can explain the preferential presentation of the Leu(33) (but not Pro(33) variant) by HLA-DR52a rather than the linked HLA-DR3 or the allelic DR52b. The modeling also predicts efficient anchoring at position 33 by several alternative hydrophobic alpha-amino acids; indeed, a recently identified variant with Val(33) is presented well to two clones, and is therefore potentially alloimmunogenic. Finally, these HPA-1a-specific T cell clones use a variety of T cell receptors, but all have a "Th1" (IFN-gamma-producing) profile and are suitable for testing selective immunotherapies that might be applicable in vivo.

A network-based method for predicting disease-causing genes

A fundamental problem in human health is the inference of disease-causing genes, with important applications to diagnosis and treatment. Previous work in this direction relied on knowledge of multiple loci associated with the disease, or causal genes for similar diseases, which limited its applicability. Here we present a new approach to causal gene prediction that is based on integrating protein-protein interaction network data with gene expression data under a condition of interest. The latter are used to derive a set of disease-related genes which is assumed to be in close proximity in the network to the causal genes. Our method applies a set-cover-like heuristic to identify a small set of genes that best "cover" the disease-related genes. We perform comprehensive simulations to validate our method and test its robustness to noise. In addition, we validate our method on real gene expression data and on gene specific knockouts. Finally, we apply it to suggest possible genes that are involved in myasthenia gravis.

Prioritizing genes of potential relevance to diseases affected by sex hormones: an example of myasthenia gravis

Background

About 5% of western populations are afflicted by autoimmune diseases many of which are affected by sex hormones. Autoimmune diseases are complex and involve many genes. Identifying these disease-associated genes contributes to development of more effective therapies. Also, association studies frequently imply genomic regions that contain disease-associated genes but fall short of pinpointing these genes. The identification of disease-associated genes has always been challenging and to date there is no universal and effective method developed.

Results

We have developed a method to prioritize disease-associated genes for diseases affected strongly by sex hormones. Our method uses various types of information available for the genes, but no information that directly links genes with the disease. It generates a score for each of the considered genes and ranks genes based on that score. We illustrate our method on early-onset myasthenia gravis (MG) using genes potentially controlled by estrogen and localized in a genomic segment (which contains the MHC and surrounding region) strongly associated with MG. Based on the considered genomic segment 283 genes are ranked for their relevance to MG and responsiveness to estrogen. The top three ranked genes, HLA-G, TAP2 and HLA-DRB1, are implicated in autoimmune diseases, while TAP2 is associated with SNPs characteristic for MG. Within the top 35 prioritized genes our method identifies 90% of the 10 already known MG-associated genes from the considered region without using any information that directly links genes to MG. Among the top eight genes we identified HLA-G and TUBB as new candidates. We show that our ab-initio approach outperforms the other methods for prioritizing disease-associated genes.

Conclusion

We have developed a method to prioritize disease-associated genes under the potential control of sex hormones. We demonstrate the success of this method by prioritizing the genes localized in the MHC and surrounding region and evaluating the role of these genes as potential candidates for estrogen control as well as MG. We show that our method outperforms the other methods. The method has a potential to be adapted to prioritize genes relevant to other diseases.

Autoimmunizing mechanisms in thymoma and thymus

Autoimmunizing mechanisms are very hard to study in humans, so we have focused on vital clues in thymomas and hyperplastic thymuses in myasthenia gravis (MG). According to our multi-step hypothesis: thymic epithelial cells (TEC) present epitopes from the isolated acetylcholine receptor (AChR) subunits they express, and autoimmunize helper T cells; subsequently, these evoke "early antibodies" that then attack rare thymic myoid cells expressing intact AChR; in the resulting germinal centers, autoantibodies diversify to recognize native AChR. We have studied: 1) thymomas, to identify autoimmunizing cell types, focusing on IFN-alpha, against which many patients have high titer autoantibodies, as in another highly informative autoimmune syndrome. Although IFN-alpha is much easier to label than the sparse and delicate AChR subunits, we have not yet located obviously autoimmunizing micro-environments; 2) hyperplastic MG thymuses, where we find (a) upregulation of complement receptors and regulators on hyperplastic TEC and deposition of activated C3b complement component on them, (b) absence of complement regulators from almost all myoid cells, indicating vulnerability to attack, and (c) deposition of C3b, and even of the terminal membrane attack complex, especially on the myoid cells close to the infiltrating germinal centers. The changes are very similar in over 50% of the so-called seronegative patients with generalized MG (SNMG) but without detectable autoantibodies against AChR or MuSK, consistently with other evidence that they belong to the spectrum of AChR-seropositive MG. Together, moreover, our findings implicate both myoid cells and TEC in autoimmunization, and thus strongly support our hypothesis.

Polymorphisms of interferon-γ, interleukin-10, and interleukin-12 genes in myasthenia gravis

To assess the involvement of polymorphisms in genetic susceptibility to myasthenia gravis (MG), this study analyzed four polymorphisms of interferon (IFN)-gamma, interleukin (IL)-10, and IL-12 genes in 115 patients and 204 healthy controls (HC). IFNG +874T carriers were less frequent in MG, in patients with anti-acetylcholine receptor (AChR) (63%) and anti-titin (56.2%) antibodies compared with HC (p = 0.01 for all, OR: 0.5, 0.5, and 0.4, respectively). The presence of thymoma was also associated with lower frequency of IFNG +874T allele (p = 0.018, OR = 0.34). At IL10, -2763A allele was found to be slightly more frequent in MG and in patients with anti-AChR than in HC group (p = 0.05, OR = 1.7, p = 0.036, OR = 1.83). However, these associations did not remain significant after correction for multiple comparisons. IL12B allele distribution was not different among groups. These data suggest that some cytokine gene polymorphisms may contribute to susceptibility to or antibody production in MG. These findings need to be replicated in further studies.

A CD40 Kozak sequence polymorphism and susceptibility to antibody-mediated autoimmune conditions: the role of CD40 tissue-specific expression

Previously, we and others have demonstrated the association of a C/T single nucleotide polymorphism (SNP), in the Kozak sequence of CD40, with Graves' disease (GD). Here, using an expanded data set of patients, we confirm the association of the CD40 SNP with GD (n=210, P=0.002, odds ratio (OR)=1.8). Subset analysis of patients with persistently elevated thyroid peroxidase (TPO) and/or thyroglobulin (Tg) antibodies (Abs), (TPO/Tg Abs), after treatment (n=126), revealed a significantly stronger association of the SNP with disease (P=5.2 x 10(-5), OR=2.5) than in GD patients who were thyroid antibody-negative. However, the CD40 SNP was not associated with TPO/Tg Abs in healthy individuals. Next, we tested the CD40 SNP for association with Myasthenia Gravis (MG), which, like GD is an antibody-mediated autoimmune condition. Analysis of 81 MG patients found no association of the SNP with disease. Functional studies revealed significant expression of CD40 mRNA and protein in the thyroid (target tissue in GD) but not in skeletal muscle (target tissue in MG). Combined, our genetic and tissue expression data suggest that the CD40 Kozak SNP is specific for thyroid antibody production involved in the etiology of GD. Increased thyroidal expression of CD40 driven by the SNP may contribute to this disease specificity.

Recent advances in the understanding and therapy of myasthenia gravis

Myasthenia gravis (MG) is a T-cell dependent autoimmune disease mediated by autoantibodies, which mainly target muscle nicotinic acetylcholine receptors (AChR) and cause loss of functional AChRs in the neuromuscular junction. Both MG and its major autoantigen are studied extensively, yet the etiology of the disease remains unclear, although it is known to be associated with the thymus. A genetic predisposition, combined with several unidentified environmental stimuli, likely creates a favorable milieu in which the disease can appear. Current research focusses on elucidating the cellular and molecular pathways of immune dysregulation, which underly MG outburst and progression. Considerable progress has been made concerning the involvement of the thymus, the identification of impaired mechanisms of immune control and the B–T-cell interaction in MG pathogenesis, while the role of chemokines arises as an intriguing new puzzle. Recent findings fueled the development of novel therapeutic approaches with some encouraging, although preliminary, results. This review summarizes recent achievements in the fields of both basic research and therapeutics.