The concept of disinhibition as a behavioral and biological trait has been considered to be involved in the etiology of alcoholism and its co-existing disorders. The magnitude and functional mapping of event-related potential P3(00) components were analyzed, in order to examine the possible response inhibition deficits in the offspring of alcoholics.
The P3 components were compared between 50 offspring of alcoholics (OA) and a matched normal control group (NC) using a visual Go/NoGo task. The low-resolution electromagnetic tomography (LORETA) was used to analyze the functional brain mapping between groups.
The results indicated that the OA group manifested decreased P3 amplitude during the NoGo but not the Go condition compared to the NC group. The voxel-by-voxel analysis in LORETA showed group differences at several brain regions including prefrontal areas during the processing of NoGo but not Go signals.
The decreased NoGo-P3 suggests that cognitive and neural disinhibition in offspring of alcoholics may serve as a neurocognitive index for a phenotypic marker in the development of alcoholism and related disorders.
Dysfunctional neural and response inhibition in the offspring of alcoholics perhaps provides an endophenotypic marker of risk for the development of alcoholism and related disorders.
P300; Go/NoGo; Inhibitory control; Offspring of Alcoholics; LORETA; Endophenotype
Major histocompatibility complex (MHC) class II alleles HLA-DQ8 and the mouse homologue I-Ag7 lacking a canonical aspartic acid residue at position β57 are associated with coeliac disease1,2 and type I diabetes3,4. However, the role of this single polymorphism in disease initiation and progression remains poorly understood. The lack of Asp 57 creates a positively charged P9 pocket, which confers a preference for negatively charged peptides. Gluten lacks such peptides, but tissue transglutaminase (TG2) introduces negatively charged residues at defined positions into gluten T-cell epitopes by deamidating specific glutamine residues5,6 on the basis of their spacing to proline residues7. The commonly accepted model, proposing that HLA-DQ8 simply favours binding of negatively charged peptides, does not take into account the fact that TG2 requires inflammation for activation8 and that T-cell responses against native gluten peptides are found9,10, particularly in children11. Here we show that β57 polymorphism promotes the recruitment of T-cell receptors bearing a negative signature charge in the complementary determining region 3β (CDR3β) during the response against native gluten peptides presented by HLA-DQ8 in coeliac disease. These T cells showed a crossreactive and heteroclitic (stronger) response to deamidated gluten peptides. Furthermore, gluten peptide deamidation extended the T-cell-receptor repertoire by relieving the requirement for a charged residue in CDR3β. Thus, the lack of a negative charge at position β57 in MHC class II was met by negatively charged residues in the T-cell receptor or in the peptide, the combination of which might explain the role of HLA-DQ8 in amplifying the T-cell response against dietary gluten.
Event-related oscillations play a key role in understanding the brain dynamics and human information processing. In the present study, the Go/No-Go paradigm has been used to examine whether alcoholics have poor inhibitory control as compared to control subjects in terms of different oscillatory brain responses. The Matching Pursuits algorithm was used to decompose the event-related EEG into oscillations of different frequencies. It was found that alcoholics (n = 58) showed significant reduction in Delta (1.0 Hz – 3.0 Hz) and Theta (3.5 Hz – 7.0 Hz) power during No-Go trials as compared to controls (n = 29). This reduction was prominent at the frontal region. The decreased delta and theta power associated with No-Go processing perhaps suggests a deficient inhibitory control and information processing mechanism. A neuro-cognitive model has been provided to explain the findings. It is suggested that the oscillatory correlates during cognitive processing can be an endophenotypic marker in alcoholism.
Event-related oscillations; Go/No-Go; alcoholism; inhibitory control; delta; theta; P300
Event-related oscillations (EROs) are increasingly being used to assess neuro-cognitive functioning in normal and clinical populations. The current study compares different frequency activities in offspring of alcoholics (OA) and in normal controls (NC) in order to examine whether the OA group exhibits any abnormality in oscillatory activity while performing a Go/NoGo task.
The S-Transform algorithm was employed to decompose the EEG signals into different time-frequency bands, and the oscillatory responses in the P300 time window (300–700 ms) was statistically analyzed in both groups.
The OA group manifested significantly decreased activity in delta (1–3 Hz), theta (4–7 Hz), and alpha1 (8–9 Hz) bands during the NoGo condition as well as reduced delta and theta activity during the Go condition. This reduction was more prominent in the NoGo than in the Go condition.
The decreased response in delta, theta, and alpha1 oscillations, especially during the NoGo condition in high risk individuals is perhaps suggestive of cognitive and neural disinhibition, and may serve as an endophenotypic marker in the development of alcoholism and/or other disinhibitory disorders.
Event-related oscillations; Go/NoGo; Offspring of Alcoholics; Delta; Theta; Endophenotype
Recent studies have linked alcoholism with a dysfunctional neural reward system. Although several electrophysiological studies have explored reward processing in healthy individuals, such studies in alcohol dependent individuals are quite rare. The present study examines theta oscillations during reward processing in abstinent alcoholics. The electroencephalogram (EEG) was recorded in 38 abstinent alcoholics and 38 healthy controls as they performed a single outcome gambling task which involved outcomes of either loss or gain of an amount (10¢ or 50¢) that was bet. Event-related theta band (3.0–7.0 Hz) power following each outcome stimulus was computed using the S-transform method. Theta power at the time window of the outcome-related negativity (ORN) and positivity (ORP) (200–500 ms) was compared across groups and outcome conditions. Additionally, behavioral data of impulsivity and task performance were analyzed. The alcoholic group showed significantly decreased theta power during reward processing compared to controls. Current Source Density (CSD) maps of alcoholics revealed weaker and diffuse source activity for all conditions and weaker bilateral prefrontal sources during the Loss 50 condition as compared to controls who manifested stronger and focused midline sources. Further, alcoholics exhibited increased impulsivity and risk-taking on the behavioral measures. A strong association between reduced anterior theta power and impulsive task-performance was observed. It is suggested that decreased power and weaker and diffuse CSD in alcoholics may be due to dysfunctional neural reward circuitry. The relationship among alcoholism, theta oscillations, reward processing and impulsivity could offer clues to understand brain circuitries that mediate reward processing and inhibitory control.
Alcoholism; Event-related oscillations (EROs); Theta power; Outcome-related negativity (ORN); Outcome-related positivity (ORP); N2, P3, Error-related negativity (ERN); Medial Frontal Negativity (MFN); Gambling task; Impulsivity; Risk-taking
Response inhibition is considered a core dimension in alcoholism and its co-existing disorders. The major objective of this study is to compare the magnitude and spatial distribution of ERP components during response activation and inhibition in alcoholics (N = 30) and normal controls (N = 30) using a visual Go/No-Go task. The results indicate that alcoholics manifest a decreased P3(00) amplitude during Go as well as No-Go conditions. The difference between Go and No-Go processing was more evident in controls than in alcoholics. The topography of current source density in alcoholics during the P3 response was found to be very different from that of normals, suggesting that alcoholics perhaps activated inappropriate brain circuitry during cognitive processing. The significantly reduced No-Go P3 along with the relatively less anteriorized CSD topography during No-Go condition suggests poor inhibitory control in alcoholics. It is proposed that the No-Go P3, the electrophysiological signature of response inhibition, can be considered as an endophenotypic marker in alcoholism.
Event-related potentials; P3; Go/No-Go; Alcoholism; Disinhibitory disorders; Inhibitory control; Endophenotype
Previously we showed that transgenic mice expressing human HLA-DR3 gene are susceptible to PLP91-110 induced experimental autoimmune encephalomyelitis (EAE) and can serve as an animal model of multiple sclerosis (MS). HLA-DR3 mice with EAE showed increased number of CD8 T cells indicating their important role in disease pathogenesis. The role of CD8 T cells in MS, an inflammatory demyelinating disease of CNS, has been enigmatic as it has been assigned both regulatory and pathogenic roles. Therefore, to evaluate the role of CD8 T cells, we generated CD8 deficient HLA-DR3 transgenic mice (DR3.CD8-/-). Immunization with PLP91-110 led to more severe EAE in DR3.CD8-/- mice compared to HLA-DR3 mice indicating a regulatory role for CD8 T cells. Interestingly, DR3.CD8-/- mice with EAE showed decreased CNS pathology compared to DR3 mice thus suggesting a pathogenic role for CD8 T cells. We show that these two subsets of CD8 T cells can be differentiated based on the surface expression of CD122 (IL-2 Rβ chain). CD8 T cells expressing CD122 (CD8+CD122+) play a regulatory role while CD8+CD122- T cells act as a pathogenic subset. CD122 expressing CD8 T cells are the regulatory subset of CD8 T cells and regulate the encephalitogenic CD4 T cells either through direct modulation of antigen presenting cells or through the release of immuno-regulatory cytokines such as IL-10, IFNγ and TGFβ. We also showed that adoptive transfer of CD8CD122-T cells caused increased spinal cord demyelination indicating that these are pathogenic subset of CD8 T cells. Our study suggests that CD8+ T cells play both regulatory as well as pathogenic role in disease pathogenesis of EAE. A better understanding of these subsets could aid in designing novel therapy for MS patients.
Experimental autoimmune encephalomyelitis; Multiple sclerosis. HLA class II transgenic mice; demyelination; cytokine; CD8 regulatory T cells
While there is extensive literature on the relationship between the P3 component of event-related potentials (ERPs) and risk for alcoholism, there are few published studies regarding other potentially important ERP components. One important candidate is the N4(00) component in the context of semantic processing, as abnormalities in this component have been reported for adult alcoholics.
A semantic priming task was administered to non-alcohol dependent male offspring (18 to 25 years) of alcoholic fathers [high risk (HR) n=23] and non-alcoholic fathers [low risk (LR) n=28], to study whether the two groups differ in terms of the N4 component. Subjects were presented with 150 words and 150 non-words. Among the words, 50 words (primed) were preceded by their antonyms (prime, n=50), whereas the remaining 50 words were unprimed. For the analysis, N4 amplitude and latency, as well as behavioral measures for the primed and unprimed words were considered.
A significant interaction effect was observed between semantic condition and group, where HR subjects did not show N4 attenuation for primed stimuli.
The lack of N4 attenuation to primed stimuli and/or inability to differentiate between primed and unprimed stimuli, without latency and reaction time being affected, suggest deficits in semantic priming, especially in semantic expectancy and/or post-lexical semantic processing in HR male offspring. Further, it indicates that it might be an electrophysiological endophenotype that reflects genetic vulnerability to develop alcoholism.
Semantic priming; N4; alcoholism; high risk; endophenotype
Event Related Potential (ERP) studies have highlighted some measures, notably P3 amplitude, that are associated with both state and trait deficits in alcoholism, while studies examining N400 amplitude in alcoholism are few. The present study aims to examine changes in the N400 component, an electrophysiological correlate of semantic priming, in event-related potentials from a lexical decision task in 87 alcohol dependent subjects and 57 community controls.
Each subject was presented with 300 stimuli sequentially in a quasi-randomized design, where 150 stimuli were words and 150 were non-words. The subjects made a lexical decision indicating the word/nonword status with a button press. Among the words, 50 words (primed) were always preceded by their antonyms (prime, n=50), whereas the remaining 50 words were unrelated. N400 amplitude and latency measures were compiled from ERPs to the primed and unprimed words. Corresponding reaction time and response characteristics were also analyzed.
Control subjects revealed a significant attenuation of the N400 response to the primed word when compared to the unprimed word. Significantly less attenuation was observed in alcohol dependent subjects. No significant group differences were seen for latency and behavioral measures. All subjects had slower RT for unprimed words compared to primed words; however significantly less reaction time savings between the unprimed and primed condition was noted for alcoholics.
These results suggest a reduced flexibility in the cognitive networks and a lack of resource optimization in alcoholics. The reduced attenuation of N400 during the primed condition in the alcohol dependent subjects may reflect an inability to engage similar neuronal substrates associated with semantic relatedness as seen in the controls. As diminished N400 attenuation during priming is observed in both alcoholics and high risk subjects, it may be a marker of risk and a good endophenotype for alcoholism.
N400; Semantic Priming; Lexical Decision; Event-Related-Potentials; Alcoholism
India has seen rapid unorganized urbanization in the past few decades. However, the burden of childhood diseases and malnutrition in such populations is difficult to quantify. The morbidity experience of children living in semi-urban slums of a southern Indian city is described.
A total of 176 children were recruited pre-weaning from four geographically adjacent, semi-urban slums located in the western outskirts of Vellore, Tamil Nadu for a study on water safety and enteric infections and received either bottled or municipal drinking water based on their area of residence. Children were visited weekly at home and had anthropometry measured monthly until their second birthday.
A total of 3932 episodes of illness were recorded during the follow-up period, resulting in an incidence of 12.5 illnesses/child-year, with more illness during infancy than in the second year of life. Respiratory, mostly upper respiratory infections, and gastrointestinal illnesses were most common. Approximately one-third of children were stunted at two years of age, and two-thirds had at least one episode of growth failure during the two years of follow up. No differences in morbidity were seen between children who received bottled and municipal water.
Our study found a high burden of childhood diseases and malnutrition among urban slum dwellers in southern India. Frequent illnesses may adversely impact children’s health and development, besides placing an additional burden on families who need to seek healthcare and find resources to manage illness.
Children; Morbidity; Incidence; Slum; Longitudinal study; India
We investigated whether treatment with gliadin induces a paracellular permeability defect that enhances bacterial translocation to mesenteric lymph nodes (MLN) via resident dendritic cells (DC) expressing TLR-2 or 4 in HCD4/HLA-DQ8 transgenic mice.
HLA-DQ8 transgenic mice were sensitized and subsequently gavaged with gliadin, in the presence or absence of AT1001 (paracellular permeability inhibitor). Non-sensitized mice were gavaged with indomethacin (permeability inducer) or rice cereal. CD11c and CD103 (DC markers) and TLR-2 and 4 were investigated by immunostaining. Intestinal permeability was assessed by paracellular flux of 51Cr-EDTA in Ussing chambers. Bacterial translocation to MLN was performed by plate counting on aerobic and anaerobic conditions.
In gliadin-treated mice, both 51Cr-EDTA flux in jejunal mucosa and aerobic and anaerobic bacterial counts in MLN were increased (p < 0.05) compared to indomethacin-treated mice and controls. The inhibitor AT1001 normalized 51Cr-EDTA flux, but had no effect on bacterial translocation in gliadin-treated mice. In addition, changes in mucosal DC marker distribution such as increased (p < 0.05) trans-epithelial CD103+ cells and reduction (p < 0.05) of CD11c immunostaining were detected in gliadin-treated mice. Moreover, changes in DC markers and TLR-2 or 4 immunophenotypes were not associated.
Pharmacological restoration of paracellular permeability was not sufficient to prevent bacterial translocation in gluten-sensitive mice. We hypothesize that transcellular mechanisms involving CD103+DC and CD11c+DC may explain in gluten-sensitive HCD4/HLA-DQ8 transgenic mice the sustained increased bacterial translocation observed in the absence of a significant inflammatory response.
Celiac disease; Dendritic cells; Toll-like receptors; Intestinal permeability; HCD4/HLA-DQ8 transgenic mice
Celiac disease (CD) is frequently diagnosed in patients with type 1 diabetes (T1D), and T1D patients can exhibit Abs against tissue transglutaminase, the auto-antigen in CD. Thus, gliadin, the trigger in CD, has been suggested to have a role in T1D pathogenesis. The objective of this study was to investigate whether gliadin contributes to enteropathy and insulitis in NOD-DQ8 mice, an animal model that does not spontaneously develop T1D. Gliadin-sensitized NOD-DQ8 mice developed moderate enteropathy, intraepithelial lymphocytosis, and barrier dysfunction, but not insulitis. Administration of anti-CD25 mAbs before gliadin-sensitization induced partial depletion of CD25+Foxp3+ T cells and led to severe insulitis, but did not exacerbate mucosal dysfunction. CD4+ T cells isolated from pancreatic lymph nodes of mice that developed insulitis showed increased proliferation and proinflammatory cytokines after incubation with gliadin but not with BSA. CD4+ T cells isolated from nonsensitized controls did not response to gliadin or BSA. In conclusion, gliadin sensitization induced moderate enteropathy in NOD-DQ8 mice. However, insulitis development required gliadin-sensitization and partial systemic depletion of CD25+Foxp3+ T cells. This humanized murine model provides a mechanistic link to explain how the mucosal intolerance to a dietary protein can lead to insulitis in the presence of partial regulatory T cell deficiency.
Although systemic lupus erythematosus (SLE) is a multigenic autoimmune disorder, HLA-D is the most dominant genetic susceptibility locus. This study was undertaken to investigate the hypothesis that microbial peptides bind HLA-DR3 and activate T cells reactive with lupus autoantigens. Using HLA-DR3 transgenic mice and lupus-associated autoantigen SmD protein, SmD79–93 was identified to contain a dominant HLA-DR3 restricted T cell epitope. This T cell epitope was characterized by using a T-T hybridoma, C1P2, generated from SmD immunized HLA-DR3 transgenic mouse. By pattern search analysis, 20 putative mimicry peptides (P2–P21) of SmD79–93, from microbial and human origin were identified. C1P2 cells responded to SmD, SmD79–93 and a peptide (P20) from Vibro cholerae. Immunization of HLA-DR3 mice with P20 induced T cell responses and IgG antibodies to SmD that were not cross-reactive with the immunogen. A T-T hybridoma, P20P1, generated from P20 immunized mice, not only responded to P20 and SmD79–93, but also to peptides from Streptococccus agalactiae (P17) and human-La related protein (P11). These three T cell mimics (P20, P11 and P17) induced diverse and different autoantibody response profiles. Our data demonstrates for the first time molecular mimicry at T cell epitope level between lupus-associated autoantigen SmD and microbial peptides. Considering distinct autoreactive T cell clones, activated by different microbial peptides, molecular mimicry at T cell epitope level can be an important pathway for the activation of autoreactive T cells resulting in the production of autoantibodies. In addition, the novel findings reported herein may have significant implications in the pathogenesis of SLE.
Epitope; HLA-DR3; Mice; Molecular Mimicry; Systemic Lupus; Erythematosus; SmD
Active delivery of recombinant autoantigens or allergens at the intestinal mucosa by genetically modified Lactococcus lactis (LL) provides a novel therapeutic approach for the induction of tolerance. Celiac disease is associated with either HLA-DQ2 or HLA-DQ8 restricted responses to specific antigenic epitopes of gliadin, and may be treated by induction of antigen-specific tolerance. We investigated whether oral administration of LL-delivered DQ8-specific gliadin epitope induces antigen-specific tolerance.
was engineered to secrete a deamidated DQ8 gliadin epitope (LL-eDQ8d) and the induction of antigen-specific tolerance was studied in NOD AB° DQ8 transgenic mice. Tolerance was assessed by delayed-type hypersensitivity reaction, cytokine measurements, eDQ8d-specific proliferation and regulatory T cell analysis. Oral administration of LL-eDQ8d induced suppression of local and systemic DQ8 restricted T-cell responses in NOD AB° DQ8 transgenic mice. Treatment resulted in an antigen-specific decrease of the proliferative capacity of inguinal lymph node cells and lamina propria cells. Production of IL-10 and TGF-β and a significant induction of Foxp3+ regulatory T-cells were associated with the eDQ8d-specific suppression induced by LL-eDQ8d.
These data provide support for the development of effective therapeutic approaches for gluten-sensitive disorders using orally administered antigen-secreting LL. Such treatments may be effective even in the setting of established hypersensitivity.
We used transgenic expression of capsid antigens to Theiler's murine encephalomyelitis virus (TMEV) to study the influence of VP1, VP2, or VP2121-130 to either protection or pathogenesis to chronic spinal cord demyelination, axonal loss and functional deficits during the acute and chronic phases of infection. We used both mice that are normally susceptible (FVB) and mice normally resistant (FVB.Db) to demyelination. Transgenic expression of VP2121-130 epitope in resistant FVB.Db mice caused spinal cord pathology and virus persistence because the VP2121-130 epitope is the dominant peptide recognized by Db, which is critical for virus clearance. In contrast, all three FVB TMEV transgenic mice showed more demyelination, inflammation, and axonal loss as compared to wild type FVB mice even though virus load was not increased. Motor function measured by rotarod showed weak correlation with total number of midthoracic axons, but a strong correlation with large caliber axons (>10μm2). This study supports the hypothesis that expression of viral capsid proteins as self influences the extent of axonal pathology following Theiler's virus-induced demyelination. The findings provide insight into the role of axonal injury in the development of functional deficits that may have relevance to human demyelinating disease.
Thyroglobulin (Tg), a homodimer of 660 kD comprising 2748 amino acids, is the largest autoantigen known. The prevalence of autoimmune thyroid disease, including Hashimoto's thyroiditis and Graves' disease, has provided the impetus for identifying pathogenic T cell epitopes from human Tg over two decades. With no known dominant epitopes, the search has long been a challenge for investigators. After identifying HLA-DRB1*03:01 (HLA-DR3) and H2Eb as susceptibility alleles for Tg-induced experimental autoimmune thyroiditis in transgenic mouse strains, we searched for naturally processed T cell epitopes with MHC class II-binding motif anchors and tested the selected peptides for pathogenicity in these mice. The thyroiditogenicity of one peptide, hTg2079, was confirmed in DR3 transgenic mice and corroborated in clinical studies. In H2Eb-expressing transgenic mice, we identified three T cell epitopes from mouse Tg, mTg179, mTg409 and mTg2342, based on homology to epitopes hTg179, hTg410 and hTg2344, respectively, which we and others have found stimulatory or pathogenic in both DR3- and H2E-expressing mice. The high homology among these peptides with shared presentation by DR3, H2Eb and H2Ek molecules led us to examine the binding pocket residues of these class II molecules. Their similar binding characteristics help explain the pathogenic capacity of these T cell epitopes. Our approach of using appropriate human and murine MHC class II transgenic mice, combined with the synthesis and testing of potential pathogenic Tg peptides predicted from computational models of MHC-binding motifs, should continue to provide insights into human autoimmune thyroid disease.
Autoimmune thyroiditis; HLA-DR3; H2E; transgenic mice; thyroglobulin peptides
We have developed a novel method for genetic characterization of single cells by integrating microfluidic stretching of chromosomal DNA and fiber fluorescence in situ hybridization (FISH). In this method, individually isolated cell nuclei were immobilized in a microchannel. Chromosomal DNA was released from the nuclei and stretched by a pressure-driven flow. We analyzed and optimized flow conditions to generate a millimeter-long band of stretched DNA from each nucleus. Telomere fiber FISH was successfully performed on the stretched chromosomal DNA. Individual telomere fiber FISH signals from single cells could be resolved and their lengths measured, demonstrating the ability of the method to quantify genetic features at the level of single cells.
Fluorescence in situ hybridization; DNA; Single cell; Microfluidic; Fiber FISH; Telomere
Noninfectious uveitis is a leading cause of blindness and is thought to involve autoimmune T cell responses to retinal proteins, e.g., retinal arrestin (S-Ag). There are no known biomarkers for the disease. Susceptibility is associated with HLA, but little is known about susceptible class II alleles or the potentially pathogenic epitopes that they present. Using a ‘humanized’ HLA-transgenic mouse model of S-Ag induced autoimmune uveitis, we identified several susceptible and resistant alleles of HLA-DR and –DQ genes and defined pathogenic epitopes of S-Ag presented by the susceptible alleles. The sequences of these epitopes overlap with some previously identified peptides of S-Ag (“M” and “N”), known to elicit memory responses in lymphocytes of uveitis patients. HLA-DR-restricted, S-Ag-specific CD4+ T cells could be detected in blood and draining lymph nodes of uveitic mice with HLA class II tetramers and transferred the disease to healthy mice. Importantly, tetramer-positive cells were detected in peripheral blood of a uveitis patient. These findings provide the first tangible evidence that an autoimmune response to retina is causally involved in pathogenesis of human uveitis, demonstrate the feasibility of identifying and isolating retinal antigen-specific T cells from uveitis patients and may facilitate their development as biomarkers for the disease.
HLA class II; Uveitis; S-antigen; Arrestin; Autoimmune biomarker
Certain class II alleles are associated with susceptibility to develop arthritis. However, some individuals carrying non-RA associated alleles develop arthritis is still unexplained. An individual heterozygous for both the DQA1 and DQB1 genes, can express the DQ molecule in cis or trans heterodimers. In a cis-heterodimer the alpha chain interacts with the beta chain coded by the same chromosome, while in a trans-heterodimer it interacts with the beta chain on the other chromosome. In this study we tried to find out if trans-heterodimer of 2 non-associated alleles, DQB1*0601 and DQB1*0604, can predispose to arthritis using a humanized mouse model of arthritis.
DQB1*0601 and *0604 occur in linkage with DQA1*0103 and *0102 respectively. To understand the role of trans-heterodimer, we generated DQB1*0604/DQA1* 0103 transgenic mice lacking endogenous class II molecules.
The DQB1*0604/A1*0103 mice developed severe arthritis and in vitro generated antigen-specific response. The DQB1*0604/DQA1*0103 could present type II collagen (CII)-derived peptides that are not presented by arthritis- resistant DQB1*0601 allele, suggesting that trans-heterodimer molecules between two DQB1 and DQA1 molecules may result in presentation of unique antigens and susceptibility to develop arthritis. Molecular modeling of the CII peptides showed that DQB1*0604/DQA1*0103 shares p4 pocket with arthritis-susceptible DQB1*0302 allele and further a critical role of p4 and p9 pockets is suggested with susceptibility to arthritis.
The present data provides a possible explanation for the parental inheritance of non-susceptible alleles in some patients with rheumatoid arthritis and a mechanism by which they can predispose to develop arthritis.
Structural diversity in the peptide binding sites of the redundant classical MHC antigen presenting molecules is strongly selected in humans and mice. Although the encoded antigen presenting molecules overlap in antigen presenting function, differences in polymorphism at the MHC I A, B and C loci in humans and higher primates indicate these loci are not functionally equivalent. The structural basis of these differences is not known. We hypothesize that classical class I loci differ in their ability to direct effective immunity against intracellular pathogens. Using a picornavirus infection model and chimeric H-2 transgenes, we examined locus specific functional determinants distinguishing the ability of class I sister genes to direct effective anti viral immunity. Whereas, parental FVB and transgenic FVB mice expressing the H-2Kb gene are highly susceptible to persisting Theiler's virus infection within the CNS and subsequent demyelination, mice expressing the Db transgene clear the virus and are protected from demyelination. Remarkably, animals expressing a chimeric transgene, comprised primarily of Kb but encoding the peptide binding domain of Db, develop a robust anti viral CTL response yet fail to clear virus and develop significant demyelination. Differences in expression of the chimeric Kbα1α2Db gene (low) and Db (high) in the CNS of infected mice mirror expression levels of their endogenous H-2q counterparts in FVB mice. These findings demonstrate that locus specific elements other than those specifying peptide binding and T cell receptor interaction can determine ability to clear virus infection. This finding provides a basis for understanding locus-specific differences in MHC polymorphism, characterized best in human populations.
MHC I genes are best understood as regulators of antiviral immunity. In humans and mice there are 2 to 3 homologous MHC I genes encoding highly polymorphic antigen presenting molecules which present virus proteins to T lymphocytes. A world wide effort has catalogued more than 6,300 classical HLA MHC I alleles in human populations, making these MHC loci among the best characterized polymorphic gene families. However, there has been little progress in understanding implications of the differences in polymorphism present at the HLA A, B, and C loci. By expressing MHC I molecules capable of presenting viral antigens under regulatory determinants from different sister MHC I genes of the mouse, we address the hypothesis that locus-specific differences in the regulation of the homologous MHC I sister genes can determine whether alleles at any particular locus can effectively target protective immunity against virus infection. We find that while the ability to activate cellular immune effectors is determined by the highly polymorphic MHC I sequences encoding the peptide binding domain, the ability of these T lymphocytes to effectively clear virus from the central nervous system can also be determined by gene sequences mapping outside of this region.
Multiple sclerosis (MS) is associated with pathogenic autoimmunity primarily focused on major CNS-myelin target antigens including myelin basic protein (MBP), proteolipidprotein (PLP), myelin oligodendrocyte protein (MOG). MS is a complex trait whereby the HLA genes, particularly class-II genes of HLA-DR15 haplotype, dominate the genetic contribution to disease-risk. Due to strong linkage disequilibrium in HLA-II region, it has been hard to establish precisely whether the functionally relevant effect derives from the DRB1*1501, DQA1*0102-DQB1*0602, or DRB5*0101 loci of HLA-DR15 haplotype, their combinations, or their epistatic interactions. Nevertheless, most genetic studies have indicated DRB1*1501 as a primary risk factor in MS. Here, we used 'HLA-humanized' mice to discern the potential relative contribution of DRB1*1501 and DQB1*0602 alleles to susceptibility to "humanized" MS-like disease induced by PLP, one of the most prominent and encephalitogenic target-antigens implicated in human MS.
The HLA-DRB1*1501- and HLA-DQB1*0602-Tg mice (MHC-II-/-), and control non-HLA-DR15-relevant-Tg mice were immunized with a set of overlapping PLP peptides or with recombinant soluble PLP for induction of "humanized" MS-like disease, as well as for ex-vivo analysis of immunogenic/immunodominant HLA-restricted T-cell epitopes and associated cytokine secretion profile.
PLP autoimmunity in both HLA-DR15-Tg mice was focused on 139-151 and 175-194 epitopes. Strikingly, however, the HLA-DRB1*1501-transgenics were refractory to disease induction by any of the overlapping PLP peptides, while HLA-DQB1*0602 transgenics were susceptible to disease induction by PLP139-151 and PLP175-194 peptides. Although both transgenics responded to both peptides, the PLP139-151- and PLP175-194-reactive T-cells were directed to Th1/Th17 phenotype in DQB1*0602-Tg mice and towards Th2 in DRB1*1501-Tg mice.
While genome studies map a strong MS susceptibility effect to the region of DRB1*1501, our findings offer a rationale for potential involvement of pathogenic DQ6-associated autoimmunity in MS. Moreover, that DQB1*0602, but not DRB1*1501, determines disease-susceptibility to PLP in HLA-transgenics, suggests a potential differential, functional role for DQB1*0602 as a predisposing allele in MS. This, together with previously demonstrated disease-susceptibility to MBP and MOG in DRB1*1501-transgenics, also suggests a differential role for DRB1*1501 and DQB1*0602 depending on target antigen and imply a potential complex 'genotype/target antigen/phenotype' relationship in MS heterogeneity.
EAE/MS; Antigens/Peptides/Epitopes; Neuroimmunology; T Cells; MHC; HLA-Tg mice
HLA class II allele DRB1*0401 is associated with predisposition to Rheumatoid Arthritis in humans as well as collagen-induced arthritis in mice. Predominantly females develop arthritis in humans and DR4 transgenic mice; however the mechanism of sex-bias is still unknown. We have investigated the molecular basis by which DR4 is associated with sex-bias of arthritis. Here we show that differential antigen-specific immune mechanisms in DR4 male and female mice lead to increased susceptibility in female mice. B cells are hyperactive and present DR-restricted peptides robustly in females compared to males. Antigen-specific response showed that females produced B cell modulating cytokines like IL-13 while males produced IFNγ. Male transgenic mice have higher number of T and B regulatory cells. An exogenous supply of 17β estradiol in male mice led to enhanced expression of DR4 and antigen-specific response to DR4-restricted peptides. On the other hand, castration increased the incidence of arthritis. We propose that sex-bias in arthritis involves B cells and presentation of antigen by HLA-DR4 leading to activation of autoreactive cells and autoantibodies production in females, while regulatory B cells in males protect them from pathogenesis. The transgenic mice expressing RA susceptible haplotype simulate human RA and may be valuable to study gender differences observed in patients.
Rheumatoid Arthritis; Transgenic mice; HLA-DR4; Sex-bias; Antigen presentation
A dysfunctional neural reward system has been shown to be associated with alcoholism. The current study aims to examine reward processing in male alcoholics by using event related potentials (ERPs) as well as behavioral measures of impulsivity and risk-taking.
Outcome related negativity (ORN/N2) and positivity (ORP/P3) derived from a single outcome gambling task were analyzed using a mixed model procedure. Current density was compared across groups and outcomes using standardized low resolution electromagnetic tomography (sLORETA). Behavioral scores were also compared across groups. Correlations of ERP factors with behavioral and impulsivity factors were also analyzed.
Alcoholics showed significantly lower amplitude than controls during all outcome conditions for the ORP component and decreased amplitude during the loss conditions for the ORN component. Within conditions, Gain produced higher amplitudes than Loss conditions. Topographically, both groups had an anterior focus during Loss conditions and posterior maxima during Gain conditions, especially for the ORN component. Decreased ORP current density at cingulate gyrus and less negative ORN current density at sensory and motor areas characterized the alcoholics. Alcoholics had higher levels of impulsivity and risk-taking features than controls.
Deficient outcome/reward processing and increased impulsivity and risk-taking observed in alcoholics may be at least partly due to reward deficiency and/or dysfunctional reward circuitry in the brain, suggesting that alcoholism can be considered as part of the cluster of the reward deficiency syndrome (RDS).
Outcome-related negativity; Outcome-related positivity; Error-related negativity; Medial Frontal Negativity; N2; P3; impulsivity; alcoholism; Reward Deficiency Syndrome