Protection against rheumatoid arthritis by HLA: nature and nurture

Association of HLA-DRB1 alleles with rheumatoid arthritis in Split-Dalmatia County in southern Croatia

OBJECTIVE

The aim of this study was to investigate the distribution of HLA-DRB1 alleles in patients with rheumatoid arthritis (RA) in the Sinj Region (SR) and the rest of the Split-Dalmatia County (SDC) in Croatia and to determine their relationship with disease severity.

METHODS

A total of 74 RA patients and 80 healthy controls from the SR, and 74 RA patients and 80 healthy controls from the rest of the SDC were genotyped using sequence-specific oligonucleotide primed PCR. High-resolution typing of HLA-DRB1*04 alleles was performed using the single specific primed polymerase chain reaction (PCR-SSP) method. Serum anti-CCP, rheumatoid factor, C‑reactive protein, and erythrocyte sedimentation rate were measured in all RA patients, whereas disease activity was assessed by DAS-28 and functional status by the Health Assessment Questionnaire Disability Index.

RESULTS

The HLA-DRB1*04 allele was more frequent in patients with RA from the SR than that in patients from the rest of the SDC (18.2% vs. 9.5%; P = 0.014), whereas the HLA-DRB1*15 allele was more frequent in patients with RA from the rest of the SDC than in patients from the SR (16.2% vs. 7.4%; P = 0.010). Shared epitope (SE) positive patients from the SR had significantly higher serum anti-CCP and RF antibody levels (P = 0.014 and P = 0.004, respectively), higher disease activity (P = 0.043), and worse functional status (P < 0.001), than SE-positive patients from the rest of the SDC.

CONCLUSION

The observed higher incidence of more severe forms of RA in the SR in comparison to the rest of the SDC might be associated with the higher incidence of HLA-DRB1*04 allele in the SR.

Association of rheumatoid arthritis and its severity with human leukocytic antigen-DRB1 alleles in Kurdish region in North of Iraq

BACKGROUND

Rheumatoid arthritis is a complex multifactorial chronic disease, the importance of human leukocytic antigen (HLA) as a major genetic risk factor for rheumatoid arthritis was studied worldwide. The objective of this study is to identify the association of HLA-DRB1 subtypes with rheumatoid arthritis and its severity in Kurdish region.

METHODS

A case-control study recruited 65 rheumatoid arthritis patients and 100 healthy individuals as control group all over the Kurdistan region/Iraq. Both patient and control groups are genotyped using polymerase chain reaction with sequence specific primer. Anti-CCP antibodies were measured by ELISA test. Rheumatoid factor, C-reactive protein, and disease activity score 28 which measured by DAS-28 values were calculated. The DAS-28 was used to assess the clinical severity of the patients.

RESULTS

HLA-DRB1-0404 and HLA-DRB1-0405 frequencies showed a strong association with disease susceptibility (P < 0.001). The frequency of HLA-DRB1-0411 and HLA-DRB1-0413 were significantly higher in control group (P < 0.001). The frequency of rheumatoid factor and Anti-CCP were significantly higher among shared epitope-positive patients compared to shared epitope-negative patients (P < 0.001). Regarding the disease activity by DAS-28, rheumatoid arthritis patients didn't show significant difference between the shared epitope-positive and shared epitope-negative patients.

CONCLUSIONS

HLA-DR0404 and HLA-DR0405 alleles are related to RA, while HLA-DR1-0411 and HLA-DRB1-0413 protect against RA in the Kurdistan region in the North of Iraq.

Immunogenicity of a rheumatoid arthritis protective sequence when acquired through microchimerism

HLA class II genes provide the strongest genetic contribution to rheumatoid arthritis (RA). HLA-DRB1 alleles encoding the sequence DERAA are RA-protective. Paradoxically, RA risk is increased in women with DERAA⁺ children born prior to onset. We developed a sensitive qPCR assay specific for DERAA, and found 53% of DERAA^-/- women with RA had microchimerism (Mc; pregnancy-derived allogeneic cells) carrying DERAA (DERAA-Mc) vs. 6% of healthy women. DERAA-Mc quantities correlated with an RA-risk genetic background including DERAA-binding HLA-DQ alleles, early RA onset, and aspects of RA severity. CD4⁺ T cells showed stronger response against DERAA⁺ vs. DERAA^- allogeneic cell lines in vitro, in line with an immunogenic role of allogeneic DERAA. Results indicate a model where DERAA-Mc activates DERAA-directed T cells that are naturally present in DERAA^-/- individuals and can have cross-reactivity against joint antigens. Moreover, we provide an explanation for the enigmatic observation that the same HLA sequence differentially affects RA risk through Mendelian inheritance vs. microchimeric cell acquisition.

Epitope Stealing as a Mechanism of Dominant Protection by HLA-DQ6 in Type 1 Diabetes

The heterozygous DQ2/8 (DQA1*05:01-DQB1*02:01/DQA1*03:01-DQB1*03:02) genotype confers the highest risk in type 1 diabetes (T1D), whereas the DQ6/8 (DQA1*02:01-DQB1*06:02/DQA1*03:01-DQB1*03:02) genotype is protective. The mechanism of dominant protection by DQ6 (DQB1*06:02) is unknown. We tested the hypothesis that DQ6 interferes with peptide binding to DQ8 by competition for islet epitope ("epitope stealing") by analysis of the islet ligandome presented by HLA-DQ6/8 and -DQ8/8 on dendritic cells pulsed with islet autoantigens preproinsulin (PPI), GAD65, and IA-2, followed by competition assays using a newly established "epitope-stealing" HLA/peptide-binding assay. HLA-DQ ligandome analysis revealed a distinct DQ6 peptide-binding motif compared with the susceptible DQ2/8 molecules. PPI and IA-2 peptides were identified from DQ6, of DQ6/8 heterozygous dendritic cells, but no DQ8 islet peptides were retrieved. Insulin B6-23, a highly immunogenic CD4 T-cell epitope in patients with T1D, bound to both DQ6 and DQ8. Yet, binding of InsB6-23 to DQ8 was prevented by DQ6. We obtained first functional evidence of a mechanism of dominant protection from disease, in which HLA molecules associated with protection bind islet epitopes in a different, competing, HLA-binding register, leading to "epitope stealing" and conceivably diverting the immune response from islet epitopes presented by disease-susceptible HLA molecules in the absence of protective HLA.

Principles of inflammasome priming and inhibition: Implications for psychiatric disorders

The production of inflammatory proteins by the innate immune system is a tightly orchestrated procedure that allows the body to efficiently respond to exogenous and endogenous threats. Recently, accumulating evidence has indicated that disturbances in the inflammatory response system not only provoke autoimmune disorders, but also can have deleterious effects on neuronal function and mental health. As inflammation in the brain is primarily mediated by microglia, there has been an expanding focus on the mechanisms through which these cells initiate and propagate neuroinflammation. Microglia can enter persistently active states upon their initial recognition of an environmental stressor and are thereafter prone to elicit amplified and persistent inflammatory responses following subsequent exposures to stressors. A recent focus on why primed microglia cells are susceptible to environmental insults has been the NLRP3 inflammasome. Its function within the innate immune system is regulated in such a manner that supports a role for the complex in gating neuroinflammatory responses. The activation of NLRP3 inflammasome in microglia results in the cleavage of zymogen inflammatory interleukins into functional forms that elicit a number of consequential effects in the local neuronal environment. There is evidence to support the principle that within primed neuroimmune systems a lowered threshold for NLRP3 activation can cause persistent neuroinflammation or the amplified production of inflammatory cytokines, such as IL-1β and IL-18. Over the course of an individual's lifetime, persistent neuroinflammation can subsequently lead to the pathophysiological signatures that define psychological disorders. Therefore, targeting the NLRP3 inflammasome complex may represent an innovative and consequential approach to limit neuroinflammatory states in psychiatric disorders, such as major depressive disorder.

Genetic variants in the HLA class II region associated with risk of cutaneous squamous cell carcinoma

BACKGROUND

The immune system has been implicated in the pathophysiology of cutaneous squamous cell carcinoma (cSCC) as evidenced by the substantially increased risk of cSCC in immunosuppressed individuals. Associations between cSCC risk and single nucleotide polymorphisms (SNPs) in the HLA region have been identified by genome-wide association studies (GWAS). The translation of the associated HLA SNPs to structural amino acids changes in HLA molecules has not been previously elucidated.

METHODS

Using data from a GWAS that included 7238 cSCC cases and 56,961 controls of non-Hispanic white ancestry, we imputed classical alleles and corresponding amino acid changes in HLA genes. Logistic regression models were used to examine associations between cSCC risk and genotyped or imputed SNPs, classical HLA alleles, and amino acid changes.

RESULTS

Among the genotyped SNPs, cSCC risk was associated with rs28535317 (OR = 1.20, p = 9.88 × 10^- 11) corresponding to an amino-acid change from phenylalanine to leucine at codon 26 of HLA-DRB1 (OR = 1.17, p = 2.48 × 10^- 10). An additional independent association was observed for a threonine to isoleucine change at codon 107 of HLA-DQA1 (OR = 1.14, p = 2.34 × 10^- 9). Among the classical HLA alleles, cSCC was associated with DRB1*01 (OR = 1.18, p = 5.86 × 10^- 10). Conditional analyses revealed additional independent cSCC associations with DQA1*05:01 and DQA1*05:05. Extended haplotype analysis was used to complement the imputed haplotypes, which identified three extended haplotypes in the HLA-DR and HLA-DQ regions.

CONCLUSIONS

Associations with specific HLA-DR and -DQ alleles are likely to explain previously observed GWAS signals in the HLA region associated with cSCC risk.

Human Leukocyte Antigen-Disease Associations in Rheumatoid Arthritis

The cause and pathogenesis of rheumatoid arthritis (RA) are influenced by environmental and genetic risk factors. Shared epitope-coding human leukocyte antigen (HLA)-DRB1 alleles increase RA risk and severity; however, the underlying mechanisms of action remain unclear. In contrast, several other DRB1 alleles protect against RA. Additionally, genome-wide association studies suggest that RA associates with other, HLA and non-HLA, genes; but the relative contributions of such risk loci to RA are incompletely understood. Future research challenges include integrating the epidemiologic and genomic data into validated arthritogenic pathways and determining the mechanisms of interaction between RA risk genes and environmental influences.

Increased risk of rheumatoid arthritis among mothers with children who carry DRB1 risk-associated alleles

OBJECTIVE

To investigate whether a child's genotype affects a mother's risk of rheumatoid arthritis (RA) beyond the risk associated with her genotype and to test whether exposure to fetal alleles inherited from the father increases risk of RA among mothers without risk alleles.

METHODS

A case-control study was conducted among 1165 mothers (170 cases/995 controls) and their respective 1482 children. We tested the association between having any child with alleles encoding amino acids (AAs) associated with RA including the 'shared epitope' (SE) and DERAA AA sequences at positions 70-74; AA valine, lysine and alanine at positions 11, 71 and 74 of HLA-DRB1; aspartic acid at position 9 of HLA-B and phenylalanine at position 9 of DPB1. We used logistic regression models to estimate OR and 95% CI for each group of alleles, adjusting for maternal genotype and number of live births.

RESULTS

We found increased risk of RA among mothers who had any child with SE (OR 3.0; 95% CI 2.0 to 4.6); DERAA (OR 1.7; 95% CI 1.1 to 2.6); or valine (OR 2.3; 95% CI 1.6 to 3.5), lysine (OR 2.3; 95% CI 1.5 to 3.4) and alanine (OR 2.8; 95% CI 1.2 to 6.4) at DRB1 positions 11, 71 and 74, respectively. Among non-carrier mothers, increased risk of RA was associated with having children who carried DERAA (OR 1.7; 95% CI 1.0 to 2.7) and alleles encoding lysine at DRB1 position 71 (OR 2.3; 95% CI 1.5 to 4.8).

CONCLUSION

Findings support the hypothesis that a child's genotype can contribute independently to risk of RA among mothers.

Immunoglobulin (Ig)G1 and IgG4 anti-cyclic citrullinated peptide (CCP) associate with shared epitope, whereas IgG2 anti-CCP associates with smoking in patients with recent-onset rheumatoid arthritis (the Swedish TIRA project)

Given the possible importance of anti-citrullinated peptide/protein antibodies (ACPA) for initiation and progression of rheumatoid arthritis (RA), extended knowledge about the different isotypes and subclasses is important. In the present study, we analysed the immunoglobulin (Ig)G subclasses regarding reactivity against cyclic citrullinated peptides (anti-CCP) among 504 clinically well-characterized patients with recent-onset RA in relation to smoking habits, shared epitope (SE) status and IgA and pan-IgG anti-CCP antibodies. All patients, regardless of pan-IgG anti-CCP status, were analysed for IgG1-4 CCP reactivity. Sixty-nine per cent were positive in any IgG anti-CCP subclass, and of these 67% tested positive regarding IgG1, 35% IgG2, 32% IgG3, and 59% IgG4 anti-CCP. Among ever-smokers the percentages of IgG2 anti-CCP (P = 0·01) and IgA anti-CCP (P = 0·002)-positive cases were significantly higher compared to never-smokers. A positive IgG anti-CCP subclass -negative cases. Combining SE and smoking data revealed that IgG1 and IgG4 anti-CCP were the IgG anti-CCP isotypes associated with expression of SE, although the lower number of patients positive for IgG2 or IgG3 anti-CCP could, however, have influenced the results. High levels of IgG2 anti-CCP were shown to correlate with expression of the 'non-SE' allele human leucocyte antigen (HLA)-DRB1*15. In conclusion, in this study we describe different risk factor characteristics across the IgG anti-CCP subclasses, where IgG2 appears similar to IgA anti-CCP regarding the predominant association with smoking, while IgG1 and IgG4 related more distinctly to the carriage of SE genes.

Common Genetic Variants Found in HLA and KIR Immune Genes in Autism Spectrum Disorder

The "common variant-common disease" hypothesis was proposed to explain diseases with strong inheritance. This model suggests that a genetic disease is the result of the combination of several common genetic variants. Common genetic variants are described as a 5% frequency differential between diseased vs. matched control populations. This theory was recently supported by an epidemiology paper stating that about 50% of genetic risk for autism resides in common variants. However, rare variants, rather than common variants, have been found in numerous genome wide genetic studies and many have concluded that the "common variant-common disease" hypothesis is incorrect. One interpretation is that rare variants are major contributors to genetic diseases and autism involves the interaction of many rare variants, especially in the brain. It is obvious there is much yet to be learned about autism genetics. Evidence has been mounting over the years indicating immune involvement in autism, particularly the HLA genes on chromosome 6 and KIR genes on chromosome 19. These two large multigene complexes have important immune functions and have been shown to interact to eliminate unwanted virally infected and malignant cells. HLA proteins have important functions in antigen presentation in adaptive immunity and specific epitopes on HLA class I proteins act as cognate ligands for KIR receptors in innate immunity. Data suggests that HLA alleles and KIR activating genes/haplotypes are common variants in different autism populations. For example, class I allele (HLA-A2 and HLA-G 14 bp-indel) frequencies are significantly increased by more than 5% over control populations (Table 2). The HLA-DR4 Class II and shared epitope frequencies are significantly above the control populations (Table 2). Three activating KIR genes: 3DS1, 2DS1, and 2DS2 have increased frequencies of 15, 22, and 14% in autism populations, respectively. There is a 6% increase in total activating KIR genes in autism over control subjects. And, more importantly there is a 12% increase in activating KIR genes and their cognate HLA alleles over control populations (Torres et al., 2012a). These data suggest the interaction of HLA ligand/KIR receptor pairs encoded on two different chromosomes is more significant as a ligand/receptor complex than separately in autism.

Collagen Specific T-Cell Repertoire and HLA-DR Alleles: Biomarkers of Active Refractory Rheumatoid Arthritis

Rheumatoid arthritis (RA) is characterized by chronic joint inflammation and associates with HLA-DRB1*04. The Collagen IIp_261-273-specific T cell repertoire in the peripheral blood of DR4 + patients at the onset of the disease shows a restricted TCR-beta chain usage among which the most frequent is TRBV25.

To define whether this group of DR4-restricted collagen-specific shared T cell could represent markers of active-severe disease and response to therapy, 90 subjects affected by early-RA were enrolled in the study; peripheral blood mononuclear cells were cultured with or without the human collagen II peptide p261-273 and were examined by immunoscope analysis for the usage of the previously identified shared TCR-beta chains.

We report that the presence of T cells carrying rearrangement TRBV25 associated with HLA-DR haplotype and disease activity. HLA-DRB1* haplotypes 04–04, 04–01 and 04–11 were significantly associated with usage of TRBV25, higher disease activity at the onset of disease and poor response to DMARDs.

Finally, the HLA-DRB1* haplotype appeared complementary with current serologic tools to predict good and poor responders in a treat to target strategy. The data reported here offer clues to predict the course of the disease and to foresee personalized treatments in RA patients.

•

In DR4 + RA patients disease activity is associated with detection of Collagen_261-273-specific T cells carrying TRBV25.

•

HLA-DR 04/04, 04/01 and 04/11 alleles were associated with TRBV25, DAS at the onset, and poor response to DMARDs.

•

These findings could lead to tailor the treatment in the subgroup of patients with an active refractory disease.

In the era of costly medical care with monoclonal antibodies and new molecules, and of an increasing request of a personalized medicine, a relevant socio-economic problem in the management of Rheumatoid Arthritis patients is the possible identification of the subgroups of poor responders to treatment. Our study aimed to detect the refractory active patients using an HLA-DR test (available in most hospital centers) combined with a relatively new biomarker of active disease expressed on the cell surface of autoreactive T cells. These tests appear complementary tools to identify the best and the poor responders to a “treat to target strategy”.

Gender-biased regulation of human IL-17-producing cells in vitro by peptides corresponding to distinct HLA-DRB1 allele-coded sequences

Susceptibility to rheumatoid arthritis (RA) is associated with HLA-DRB1 alleles coding a 5-amino acid sequence motif called the shared epitope (SE). To explore the potential mechanisms that lead to RA susceptibility, we analyze the in vitro effect of peptides bearing different HLA-DR4 sequences on human peripheral blood-derived cells. Three 15-mer peptides were used: 65-79*0401 (an HLA-DRB1*04:01-coded sequence carrying the SE motif, QKRAA); 65-79*0402 (an HLA-DRB1*04:02-coded sequence carrying a SE-negative motif, DERAA); 65-79*0403 (an HLA-DRB1*04:03-coded sequence carrying a SE-negative motif, QRRAE). We found that CD4 TH17 cells are regulated by peptide treatment with gender bias. In male-derived T cells, all peptide treatments significantly reduced TH17 cell differentiation in vitro when compared to no peptide treatment, and to female samples. TH17 differentiation in samples not treated with peptides, either in the presence or absence of TH17-polarizing cytokines, was higher in males than in females; however, in unfractionated PBMC after treatment with TH17 polarizing cytokines, IL-17A positive cells were more abundant in females than in males. In addition, SE-positive females showed a significantly higher percentage of IL-17A-positive cells compared to SE-negative females. In conclusion, donor's SE status and gender may both influence TH17 immune polarization.

HLA class II molecules influence susceptibility versus protection in inflammatory diseases by determining the cytokine profile

The MHC in humans encodes the most polymorphic genes, the HLA genes, which are critical for the immune system to clear infection. This can be attributed to strong selection pressure as populations moved to different parts of the world and encountered new kinds of infections, leading to new HLA class II alleles. HLA genes also have the highest relative risk for autoimmune diseases. Three haplotypes, that is, HLA-DR2DQ6, DR4DQ8, and DR3DQ2, account for HLA association with most autoimmune diseases. We hypothesize that these haplotypes, along with their multiple subtypes, have survived bottlenecks of infectious episodes in human history because of their ability to present pathogenic peptides to activate T cells that secrete cytokines to clear infections. Unfortunately, they also present self-peptides/mimics to activate autoreactive T cells secreting proinflammatory cytokines that cause autoimmune diseases.

Pregnancy and the risk of rheumatoid arthritis in a highly predisposed North American Native population

OBJECTIVE

To examine reproductive history and rheumatoid arthritis (RA) risk in a highly predisposed population of North American Natives (NAN) with unique fertility characteristics.

METHODS

The effect of pregnancy on the risk of RA was examined by comparing women enrolled in 2 studies: a study of RA in NAN patients and their unaffected relatives; and NAN patients with RA and unrelated healthy NAN controls enrolled in a study of autoimmunity. All participants completed questionnaires detailing their reproductive history.

RESULTS

Patients with RA (n = 168) and controls (n = 400) were similar overall in age, education, shared epitope frequency, number of pregnancies, age at first pregnancy, smoking, and breastfeeding history. In multivariate analysis, for women who had ≥ 6 births the OR for developing RA was 0.43 (95% CI 0.21-0.87) compared with women who had 1-2 births (p = 0.046); for women who gave birth for the first time after age 20 the OR for developing RA was 0.33 (95% CI 0.16-0.66) compared with women whose first birth occurred at age ≤ 17 (p = 0.001). The highest risk of developing RA was in the first postpartum year (OR 3.8; 95% CI 1.45-9.93) compared with subsequent years (p = 0.004).

CONCLUSION

In this unique population, greater parity significantly reduced the odds of RA; an early age at first birth increased the odds, and the postpartum period was confirmed as high risk for RA onset. The protective effect of repeated exposure to the ameliorating hormonal and immunological changes of pregnancy may counterbalance the effect of early exposure to the postpartum reversal of these changes.

Increased frequency of complement C4B deficiency in rheumatoid arthritis

OBJECTIVE

To assess the copy number variation of complement C4A and C4B genes in patients with rheumatoid arthritis (RA).

METHODS

DNA samples were obtained from 299 patients and controls and analyzed for copy number variation of total complement C4, C4A, and C4B genes. The results were compared by chi-square analysis, and odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

Chi-square analysis revealed similar distribution patterns of total C4 alleles in RA patients (n = 160), non-RA patients (n = 88), and healthy controls (n = 51). There was no trend toward C4A deficiency as in lupus. Significant differences in C4B distribution were observed in RA patients, in whom an ∼2-fold increase in the frequency of homozygous and/or heterozygous C4B deficiency (0 or 1 allele) (40%) was present relative to non-RA patients or healthy controls (both 21.6%). C4B deficiency was more frequent in seropositive RA patients than in seronegative RA patients (44% versus 31%). The odds of C4B deficiency were 2.99 (95% CI 1.58-5.65) (P = 0.0006) in seropositive RA patients relative to non-RA controls. These findings were confirmed in a larger healthy control cohort, yielding an OR of 1.83 (95% CI 1.21-2.76) (P = 0.0056). The association of the shared epitope with C4B deficiency was significantly greater in seropositive RA patients than in non-seropositive RA controls (96% versus 54.5%) (P < 0.0001), suggesting that C4B deficiency interacts with the shared epitope in the development of seropositive RA.

CONCLUSION

Our findings indicate a relationship between C4B copy number variation and RA that approximates that seen between C4A copy number variation and lupus. The concurrence of C4B deficiency and the shared epitope in seropositive RA may have broad implications for our understanding of RA pathogenesis.

Precipitating and perpetuating factors of rheumatoid arthritis immunopathology: linking the triad of genetic predisposition, environmental risk factors and autoimmunity to disease pathogenesis

Rheumatoid arthritis (RA) is considered to occur when genetic and environmental factors interact to trigger immunopathological changes and consequently an inflammatory arthritis. Over the last few decades, epidemiological and genetic studies have identified a large number of risk factors for RA development, the most prominent of which comprise cigarette smoking and the shared epitope alleles. These risks appear to differ substantially between anti-cyclic citrullinated peptide (ACPA)-positive and ACPA-negative disease. In this article, we will summarise the risk factors for RA development that have currently been identified, outlining the specific gene-environment and gene-gene interactions that may occur to precipitate and perpetuate autoimmunity and RA. We will also focus on how this knowledge of risk factors for RA may be implemented in the future to identify individuals at a high risk of disease development in whom preventative strategies may be undertaken.

Bare lymphocyte syndrome: an opportunity to discover our immune system

Bare lymphocyte syndrome (BLS) is a rare immunodeficiency disorder manifested by the partial or complete disappearance of major histocompatibility complex (MHC) proteins from the surface of the cells. Based on this specific feature, it is categorized into three different types depending on which type of MHC protein is affected. These proteins are mainly involved in generating the effective immune responses by differentiating 'self' from 'non-self' antigens through a process referred to as antigen presentation. Investigations on BLS have immensely contributed to our understanding of the transcriptional regulation of these molecules and have led to the discovery of several important proteins of the antigen presentation pathway. Reviews on this subject consistently project type II BLS, MHC II deficiency as BLS syndrome, although literatures' document cases of other types of BLS too. Therefore, in this article, we have assembled information on the BLS syndrome to produce a systematic narration while emphasizing the importance of BLS system in studying various aspects of immune biology.

Association of KCNB1 to rheumatoid arthritis via interaction with HLA-DRB1

With the rapid development of large-scale high-throughput genotyping technology, genome-wide association studies have become a popular approach to mapping genes underlying common human disorders. Some genes are discovered, but many more have not been. Because these genes were not initially identified, it is reasonable to assume that their main effect is weak. We propose a method to accommodate such a situation. It is applied to the Genetic Analysis Workshop 16 Problem 1 case-control data in which shared-epitope alleles of HLA-DRB1 show very strong association with rheumatoid arthritis. Because some previous functional studies have reported association of gene KCNB1 to rheumatoid arthritis, we evaluate whether the gene KCNB1 contributes to the genetics of rheumatoid arthritis in this data set. Fifteen single-nucleotide polymorphisms from this gene were chosen. The association of KCNB1 gene to rheumatoid arthritis seems to be moderate.

Effect of human leukocyte antigen homozygosity on rubella vaccine-induced humoral and cell-mediated immune responses

Human leukocyte antigen (HLA) genes play a critical role in host immunity, including vaccine responses. HLA molecules present antigenic peptides to T cells and provide inhibitory signals to NK cells, and polymorphisms within HLA genes allow binding and presentation of a diverse array of self and foreign peptides. Heterozygosity across HLA alleles has been found to play a positive role in host defense for a variety of infections. Homozygosity within one or more HLA loci may restrict this epitope repertoire and limit T-cell responses to infection or vaccination. Here we report that homozygosity within the HLA DPB1 locus is associated with increased levels of rubella-specific IgG, an effect driven by a common allele DPB1*0401. We also show that homozygosity within different HLA class I and class II loci is correlated with variations (but not necessarily decreases) in interleukin (IL)-2, IL-5, and IL-10 secretion after rubella virus stimulation.

[Autoimmunity. Physiological control mechanisms and pathways to autoimmune disease]

Immunological tolerance towards self antigens is ensured by at least two different mechanisms, i.e. the deletion of potentially autoreactive T-lymphocytes in the thymus ("negative selection") and the active suppression of unwanted (auto)immune responses in the periphery through regulatory T-cells (Treg). With few exceptions, autoimmune diseases result from a multifactorial disturbance of the physiological immune homeostasis. Underlying mechanisms include a genetic predisposition and an aberrant activation of the immune system due to exogenous stimuli such as infectious microorganisms or endogenous stimuli such as disturbed epithelial barrier function. Microbe-derived Toll-like receptor ligands interfere with the control of immune cell activation at several levels including stimulation of autoreactive B-lymphocytes, promotion of autoantigen presentation to T-lymphocytes, and modulation of the suppressive capacity of Treg. In addition, recent evidence indicates that the newly discovered interleukin-17 producing Th(17) T-cells play an important role in promoting inflammatory reactions and tissue destruction in autoimmune diseases.

[Treating undifferentiated arthritis. What, when, how and how long?]

With the establishment of early arthritis clinics, patients can now be increasingly attended early in the course of their disease. This means that a significant proportion of these patients cannot be classified into a specific diagnosis using the traditional American College of Rheumatology (ACR) classification criteria. In these patients with undifferentiated arthritis (UA), even more important than assigning a diagnosis is the need to distinguish between patients who will develop a persistent and/or erosive disease and will be candidates for prompt treatment with disease-modifying antirheumatic drugs (DMARD), and patients in whom the disease is self limiting. Serologic markers in combination with clinical features at presentation, integrated into predictive models, are the tools currently available to the clinician for identifying these patients. Several studies have demonstrated the advantages of early treatment in UA.