Evidence for the effects of a superantigen in rheumatoid arthritis

Antigen-driven T cell responses in rheumatic diseases: insights from T cell receptor repertoire studies

Advances in T cell receptor (TCR) profiling techniques have substantially improved our ability to investigate T cell responses to antigens that are presented on HLA class I and class II molecules and associations between autoimmune T cells and rheumatic diseases. Early-stage studies in axial spondyloarthritis (axSpA) identified disease-associated T cell clonotypes, benefiting from the relative genetic homogeneity of the disease. However, both the genetic and the T cell immunological landscape are more complex in other rheumatic diseases. The diversity or redundancy in the TCR repertoire, epitope spreading over disease duration, genetic heterogeneity of HLA genes or other loci, and the diversity of epitopes contributing to disease pathogenesis and persistent inflammation are all likely to contribute to this complexity. TCR profiling holds promise for identifying key antigenic drivers and phenotypic T cell states that sustain autoimmunity in rheumatic diseases. Here, we review key findings from TCR repertoire studies in axSpA and other chronic inflammatory rheumatic diseases including psoriatic arthritis, rheumatoid arthritis, systemic lupus erythematosus and Sjögren syndrome. We explore how TCR profiling technologies, if applied to better controlled studies focused on early disease stages and genetically homogeneous subsets, can facilitate disease monitoring and the development of therapeutics targeting autoimmune T cells, their cognate antigens, or their underlying biology.

Endogenous antigens shape the transcriptome and TCR repertoire in an autoimmune arthritis model

The development of pathogenic autoreactive CD4+ T cells, particularly in the context of impaired signaling, remains poorly understood. Unraveling how defective signaling pathways contribute to their activation and persistence is crucial for identifying new therapeutic targets. We performed bulk and single-cell RNA-Seq (scRNA-Seq) and single-cell T cell receptor sequencing (scTCR-Seq) to profile a highly arthritogenic subset of naive CD4+ T cells from BALB/c-Zap70*W163C (SKG) mice, which develop CD4+ T cell-mediated autoimmune arthritis driven by a hypomorphic mutation in Zap70 - a key TCR signaling kinase. Despite impaired signaling, these cells exhibited heightened expression of T cell activation and cytokine signaling genes but diminished expression of a subset of tolerogenic markers (Izumo1r, Tnfrsf9, Cd5, S100a11) compared with WT cells. The arthritogenic cells showed an enrichment for TCR variable β (Vβ) chains targeting superantigens (Sags) from the endogenous mouse mammary tumor virus (MMTV) but exhibited diminished induction of tolerogenic markers following peripheral antigen encounter, contrasting with the robust induction of the negative regulators seen in WT cells. In arthritic joints, cells expressing Sag-reactive Vβs expanded alongside detectable MMTV proviruses. Antiretroviral treatment and Sag-reactive T cell depletion curtailed SKG arthritis, suggesting that endogenous retroviruses disrupted peripheral tolerance and promoted the activation and differentiation of autoreactive CD4+ T cells into pathogenic effector cells.

Novel insights into the immune response to bacterial T cell superantigens

Bacterial T cell superantigens (SAgs) are a family of microbial exotoxins that function to activate large numbers of T cells simultaneously. SAgs activate T cells by direct binding and crosslinking of the lateral regions of MHC class II molecules on antigen-presenting cells with T cell receptors (TCRs) on T cells; these interactions alter the normal TCR-peptide-MHC class II architecture to activate T cells in a manner that is independent of the antigen specificity of the TCR. SAgs have well-recognized, central roles in human diseases such as toxic shock syndrome and scarlet fever through their quantitative effects on the T cell response; in addition, numerous other consequences of SAg-driven T cell activation are now being recognized, including direct roles in the pathogenesis of endocarditis, bloodstream infections, skin disease and pharyngitis. In this Review, we summarize the expanding family of bacterial SAgs and how these toxins can engage highly diverse adaptive immune receptors. We highlight recent findings regarding how SAg-driven manipulation of the adaptive immune response may operate in multiple human diseases, as well as contributing to the biology and life cycle of SAg-producing bacterial pathogens.

Application of T-cell receptor repertoire as a novel monitor in dynamic tracking and assessment: A cohort-study based on RA patients

T-cell receptor repertoire (TCRR) sequencing has been widely applied in many fields as a novel tool. This study explored characteristics of TCRR in detail with a cohort of 598 rheumatoid arthritis (RA) patients before and after anti-rheumatic treatments. We highlighted the abnormal TCRR distribution in RA characterized by decreased diversity and increased proportion of hyperexpanded clones (HECs), which was potentially attributed to skewed usage of global V/J segments but not a few certain ones. Enriched motifs analysis in RA community demonstrated the huge heterogeneity of CDR3 sequences, so that individual factors are strongly recommended to be taken into consideration when it comes to clinical application of TCRR. Disease-modifying antirheumatic drugs (DMARDs) can regulate immune system through recovery of TCRR richness to relieve symptoms. Remarkably, sensitive gene profile and advantageous gene profile were identified in this study as new biomarkers for different DMARDs regimens.

Superantigens, a Paradox of the Immune Response

Staphylococcal enterotoxins are a wide family of bacterial exotoxins with the capacity to activate as much as 20% of the host T cells, which is why they were called superantigens. Superantigens (SAgs) can cause multiple diseases in humans and cattle, ranging from mild to life-threatening infections. Almost all S. aureus isolates encode at least one of these toxins, though there is no complete knowledge about how their production is triggered. One of the main problems with the available evidence for these toxins is that most studies have been conducted with a few superantigens; however, the resulting characteristics are attributed to the whole group. Although these toxins share homology and a two-domain structure organization, the similarity ratio varies from 20 to 89% among different SAgs, implying wide heterogeneity. Furthermore, every attempt to structurally classify these proteins has failed to answer differential biological functionalities. Taking these concerns into account, it might not be appropriate to extrapolate all the information that is currently available to every staphylococcal SAg. Here, we aimed to gather the available information about all staphylococcal SAgs, considering their functions and pathogenicity, their ability to interact with the immune system as well as their capacity to be used as immunotherapeutic agents, resembling the two faces of Dr. Jekyll and Mr. Hyde.

Examining pathogenic concepts of autoimmune hepatitis for cues to future investigations and interventions

BACKGROUND

Multiple pathogenic mechanisms have been implicated in autoimmune hepatitis, but they have not fully explained susceptibility, triggering events, and maintenance or escalation of the disease. Furthermore, they have not identified a critical defect that can be targeted. The goals of this review are to examine the diverse pathogenic mechanisms that have been considered in autoimmune hepatitis, indicate investigational opportunities to validate their contribution, and suggest interventions that might evolve to modify their impact. English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed. Genetic and epigenetic factors can affect susceptibility by influencing the expression of immune regulatory genes. Thymic dysfunction, possibly related to deficient production of programmed cell death protein-1, can allow autoreactive T cells to escape deletion, and alterations in the intestinal microbiome may help overcome immune tolerance and affect gender bias. Environmental factors may trigger the disease or induce epigenetic changes in gene function. Molecular mimicry, epitope spread, bystander activation, neo-antigen production, lymphocytic polyspecificity, and disturbances in immune inhibitory mechanisms may maintain or escalate the disease. Interventions that modify epigenetic effects on gene expression, alter intestinal dysbiosis, eliminate deleterious environmental factors, and target critical pathogenic mechanisms are therapeutic possibilities that might reduce risk, individualize management, and improve outcome. In conclusion, diverse pathogenic mechanisms have been implicated in autoimmune hepatitis, and they may identify a critical factor or sequence that can be validated and used to direct future management and preventive strategies.

Dendritic cells, T cells and their interaction in rheumatoid arthritis

Dendritic cells (DCs) are the key professional antigen-presenting cells which bridge innate and adaptive immune responses, inducing the priming and differentiation of naive to effector CD4+ T cells, the cross-priming of CD8+ T cells and the promotion of B cell antibody responses. DCs also play a critical role in the maintenance of immune homeostasis and tolerance. DC-T cell interactions underpin the generation of an autoimmune response in rheumatoid arthritis (RA). Here we describe the function of DCs and review evidence for DC and T cell involvement in RA pathogenesis, in particular through the presentation of self-peptide by DCs that triggers differentiation and activation of autoreactive T cells. Finally, we discuss the emerging field of targeting the DC-T cell interaction for antigen-specific immunotherapy of RA.

Streptococcal pharyngitis and rheumatic heart disease: the superantigen hypothesis revisited

Streptococcus pyogenes is a human-specific and globally prominent bacterial pathogen that despite causing numerous human infections, this bacterium is normally found in an asymptomatic carrier state. This review provides an overview of both bacterial and human factors that likely play an important role in nasopharyngeal colonization and pharyngitis, as well as the development of acute rheumatic fever and rheumatic heart disease. Here we highlight a recently described role for bacterial superantigens in promoting acute nasopharyngeal infection, and discuss how these immune system activating toxins could be crucial to initiate the autoimmune process in rheumatic heart disease.

Superantigens: The Good, the Bad, and the Ugly

Increasing evidence suggests that superantigens play a role in Immune-mediated diseases. Superantigens are potent activators of CD4* T cells, causing rapid and massive proliferation of cells and cytokine production. This characteristic of superantigens can be exploited in diseases where strong immunologic responses are required, such as in the B16F10 animal model of melanoma. Superantigen administration is able to significantly enhance Ineffective anti-tumor Immune responses, resulting in potent and long-lived protective anti-tumor immunity. However, superantigens are more well-known for the role they play in diseases. Studies using an animal model for neurologic demy-elinatlng diseases such as multiple sclerosis show that superantigens can induce severe relapses and activate auto-reactive T cells not involved in the Initial bout of disease. This may also involve epitope spreading of disease. Superantigens have also been implicated in acute diseases such as food poisoning and TSS, and in chronic diseases such as psoriasis and rheumatoid arthritis. Viral superantigens are also involved in the disease process, including superantigens derived from human Immunodeficiency virus and mouse mammary tumor virus. Finally, immunotherapies that ameliorate the role played by superantigens in disease are discussed.

Possible Role of Staphylococcal Enterotoxin B in the Pathogenesis of Autoimmune Diseases

As a member of superantigens (SAgs) produced by Staphylococcus aureus, staphylococcal enterotoxin B (SEB) is a exotoxin superantigen that can regulate the activity of immunomodulatory and pro-inflammatory cell types. In addition, SEB plays a critical role in the pathogenesis of autoimmune disorders either by initiating the autoimmune process or by inducing a relapse in an individual in clinical remission from an autoimmune disorder. SEB can directly activate T lymphocytes, leading to the release of cytokines, superoxides, or other mediators of inflammation either directly or indirectly, because of its unique ability to cross-link human major histocompatibility complex (MHC) class II and T cell receptors (TCR), forming a trimolecular complex. This review discusses the potential effects of SEB in the pathogenesis of autoimmune diseases such as multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis, and explores some updated therapeutic medications to neutralize SEB.

Microbial Infection and Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a complex autoimmune disease affecting 1–2% of general worldwide population. The etiopathogenesis of RA involves the interplay of multiple genetic risk factors and environmental triggers. Microbial infections are believed to play an important role in the initiation and perpetuation of RA. Recent clinical studies have shown the association of microbial infections with RA. Accumulated studies using animal models have also found that microbial infections can induce and/or exaggerate the symptoms of experimental arthritis. In this review, we have identified the most common microbial infections associated with RA in the literature and summarized the current evidence supporting their pathogenic role in RA. We also discussed the potential mechanisms whereby infection may promote the development of RA, such as generation of neo-autoantigens, induction of loss of tolerance by molecular mimicry, and bystander activation of the immune system.

Chronic exposure to staphylococcal superantigen elicits a systemic inflammatory disease mimicking lupus

Chronic nasal and skin colonization with superantigen (SAg)-producing Staphylococcus aureus is well documented in humans. Given that trans-mucosal and trans-cutaneous absorption of SAgs can occur, we determined whether chronic exposure to small amounts of SAg per se could activate autoreactive CD4(+) and CD8(+) T cells and precipitate any autoimmune disease without further external autoantigenic stimulation. Because HLA class II molecules present SAg more efficiently than do mouse MHC class II molecules, HLA-DQ8 transgenic mice were implanted s.c. with mini-osmotic pumps capable of continuously delivering the SAg, staphylococcal enterotoxin B (total of 10 μg/mouse), or PBS over 4 wk. Chronic exposure to staphylococcal enterotoxin B resulted in a multisystem autoimmune inflammatory disease with features similar to systemic lupus erythematosus. The disease was characterized by mononuclear cell infiltration of lungs, liver, and kidneys, accompanied by the production of anti-nuclear Abs and deposition of immune complexes in the renal glomeruli. The inflammatory infiltrates in various organs predominantly consisted of CD4(+) T cells bearing TCR Vβ8. The extent of immunopathology was markedly reduced in mice lacking CD4(+) T cells and CD28, indicating that the disease is CD4(+) T cell mediated and CD28 dependent. The absence of disease in STAT4-deficient, as well as IFN-γ-deficient, HLA-DQ8 mice suggested the pathogenic role of Th1-type cytokines, IL-12 and IFN-γ. In conclusion, our study suggests that chronic exposure to extremely small amounts of bacterial SAg could be an etiological factor for systemic lupus erythematosus.

A practical approach to T-cell receptor cloning and expression

Although cloning and expression of T-cell Receptors (TcRs) has been performed for almost two decades, these procedures are still challenging. For example, the use of T-cell clones that have undergone limited expansion as starting material to limit the loss of interesting TcRs, must be weighed against the introduction of mutations by excess PCR cycles. The recent interest in using specific TcRs for cancer immunotherapy has, however, increased the demand for practical and robust methods to rapidly clone and express TcRs. Two main technologies for TcR cloning have emerged; the use of a set of primers specifically annealing to all known TcR variable domains, and 5′-RACE amplification. We here present an improved 5′-RACE protocol that represents a fast and reliable way to identify a TcR from 10⁵ cells only, making TcR cloning feasible without a priori knowledge of the variable domain sequence. We further present a detailed procedure for the subcloning of TcRα and β chains into an expression system. We show that a recombination-based cloning protocol facilitates simple and rapid transfer of the TcR transgene into different expression systems. The presented comprehensive method can be performed in any laboratory with standard equipment and with a limited amount of starting material. We finally exemplify the straightforwardness and reliability of our procedure by cloning and expressing several MART-1-specific TcRs and demonstrating their functionality.

The role of atorvastatin in regulating the immune response leading to vascular damage in a model of Kawasaki disease

Superantigens have been implicated in a number of diseases including Kawasaki disease (KD), a multi-system vasculitis resulting in coronary artery aneurysms. We have characterized a murine disease model in which coronary arteritis is induced by a novel superantigen found in Lactobacillus casei cell wall extract (LCWE). Using this animal model of KD, we have identified three pathogenic steps leading to coronary artery aneurysm formation. These steps include T cell activation and proliferation, production of the proinflammatory cytokine tumour necrosis factor (TNF)-α and up-regulation of matrix metalloproteinase 9 (MMP-9), an elastolytic protease. In addition to their cholesterol-lowering effects, 3-hydroxy-3-methylglutaryl (HMG) coenzyme A (CoA) reductase inhibitors (statins) have pleotropic immunomodulatory properties. Thus, we examined the effect of atorvastatin in modulating each of these three critical pathogenic processes leading to aneurysm formation in the disease model. Atorvastatin inhibited lymphocyte proliferation in response to superantigen stimulation in a dose-dependent manner. This inhibition was also observed for production of soluble mediators of inflammation including interleukin (IL)-2 and TNF-α. The inhibitory effect on proliferation was rescued completely by mevalonic acid, confirming that the mechanism responsible for this inhibitory activity on immune activation was inhibition of HMG-CoA reductase. Similarly, TNF-α-induced MMP-9 production was reduced in a dose-dependent manner in response to atorvastatin. Inhibition of extracellular-regulated kinase (ERK) phosphorylation appears to be the mechanism responsible for inhibition of MMP-9 production. In conclusion, atorvastatin is able to inhibit critical steps known to be important in the development of coronary aneurysms, suggesting that statins may have therapeutic benefit in patients with KD.

Multiple roles of Staphylococcus aureus enterotoxins: pathogenicity, superantigenic activity, and correlation to antibiotic resistance

Heat-stable enterotoxins are the most notable virulence factors associated with Staphylococcus aureus, a common pathogen associated with serious community and hospital acquired diseases. Staphylococcal enterotoxins (SEs) cause toxic shock-like syndromes and have been implicated in food poisoning. But SEs also act as superantigens that stimulate T-cell proliferation, and a high correlation between these activities has been detected. Most of the nosocomial S. aureus infections are caused by methicillin-resistant S. aureus (MRSA) strains, and those resistant to quinolones or multiresistant to other antibiotics are emerging, leaving a limited choice for their control. This review focuses on these diverse roles of SE, their possible correlations and the influence in disease progression and therapy.

The glucocorticoid receptor: a revisited target for toxins

The hypothalamic-pituitary-adrenal (HPA) axis activation and glucocorticoid responses are critical for survival from a number of bacterial, viral and toxic insults, demonstrated by the fact that removal of the HPA axis or GR blockade enhances mortality rates. Replacement with synthetic glucocorticoids reverses these effects by providing protection against lethal effects. Glucocorticoid resistance/insensitivity is a common problem in the treatment of many diseases. Much research has focused on the molecular mechanism behind this resistance, but an area that has been neglected is the role of infectious agents and toxins. We have recently shown that the anthrax lethal toxin is able to repress glucocorticoid receptor function. Data suggesting that the glucocorticoid receptor may be a target for a variety of toxins is reviewed here. These studies have important implications for glucocorticoid therapy.

Clonal expansions in selected TCR BV families of rheumatoid arthritis patients are reduced by treatment with the TNFα inhibitors etanercept and infliximab

Clonal expansions of autoreactive CD4+ T cells are frequently present in patients with rheumatoid arthritis (RA) and are stable over long periods of time. This study was undertaken to investigate the influence of anti-TNFα treatment on such clonal expansions in the peripheral CD4+ T-cell compartment. TNFα inhibiting therapies significantly reduced the total number of expanded clonotypes. This effect was mainly observed in clonal expansions in the BV6 family, while in clonal expansions of the BV14 family no such effect was seen. No change in the percentage of CD4+ CD28 null T cells was observed. Serum concentrations of the pro-homeostatic cytokine IL-7 were found to increase in patients responding TNFα-inhibiting therapy. These data argue for a normalization of adaptive immune mechanisms under TNFα inhibiting therapies, which may be secondary to the control of inflammation but contribute to the efficacy of cytokine blockade therapy.

Regulation and dysregulation of immunoglobulin E: a molecular and clinical perspective

BACKGROUND

Altered levels of Immunoglobulin E (IgE) represent a dysregulation of IgE synthesis and may be seen in a variety of immunological disorders. The object of this review is to summarize the historical and molecular aspects of IgE synthesis and the disorders associated with dysregulation of IgE production.

METHODS

Articles published in Medline/PubMed were searched with the keyword Immunoglobulin E and specific terms such as class switch recombination, deficiency and/or specific disease conditions (atopy, neoplasia, renal disease, myeloma, etc.). The selected papers included reviews, case reports, retrospective reviews and molecular mechanisms. Studies involving both sexes and all ages were included in the analysis.

RESULTS

Both very low and elevated levels of IgE may be seen in clinical practice. Major advancements have been made in our understanding of the molecular basis of IgE class switching including roles for T cells, cytokines and T regulatory (or Treg) cells in this process. Dysregulation of this process may result in either elevated IgE levels or IgE deficiency.

CONCLUSION

Evaluation of a patient with elevated IgE must involve a detailed differential diagnosis and consideration of various immunological and non-immunological disorders. The use of appropriate tests will allow the correct diagnosis to be made. This can often assist in the development of tailored treatments.

Self-organized criticality theory of autoimmunity

Background

The cause of autoimmunity, which is unknown, is investigated from a different angle, i.e., the defect in immune ‘system’, to explain the cause of autoimmunity.

Methodology/Principal Findings

Repeated immunization with antigen causes systemic autoimmunity in mice otherwise not prone to spontaneous autoimmune diseases. Overstimulation of CD4⁺ T cells led to the development of autoantibody-inducing CD4⁺ T (aiCD4⁺ T) cell which had undergone T cell receptor (TCR) revision and was capable of inducing autoantibodies. The aiCD4⁺ T cell was induced by de novo TCR revision but not by cross-reaction, and subsequently overstimulated CD8⁺ T cells, driving them to become antigen-specific cytotoxic T lymphocytes (CTL). These CTLs could be further matured by antigen cross-presentation, after which they caused autoimmune tissue injury akin to systemic lupus erythematosus (SLE).

Conclusions/Significance

Systemic autoimmunity appears to be the inevitable consequence of over-stimulating the host's immune ‘system’ by repeated immunization with antigen, to the levels that surpass system's self-organized criticality.

Regulatory T Cells in Autoimmune Diseases: Anti-Ergotypic T Cells

T regulatory cells play an important role in regulating T-cell responses to self-antigens and control autoimmunity and autoimmune disease. Anti-ergotypic T cells are a subset of such regulatory T cells that respond to activation markers, ergotopes, expressed on other activated T cells. Anti-ergotypic T cells do not respond to nonactivated T cells. Ergotopes include the a-chain of the IL-2 receptor (CD25). Anti-ergotypic T cells were found to downregulate experimental diseases such as experimental autoimmune encephalomyelitis (EAE) and adjuvant arthritis (AA). Anti-ergotypic T cells are present in humans and are activated after T-cell vaccination. Here we review anti-ergotypic T cells in animal models and in humans and contrast anti-ergotypic T cells with other regulatory T-cell subsets.

Lipid-derived free radical production in superantigen-induced interstitial pneumonia

We studied the free radical generation involved in the development of interstitial pneumonia (IP) in an animal model of autoimmune disease. We observed an electron spin resonance (ESR) spectrum of alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) radical adducts detected in the lipid extract of lungs in autoimmune-prone mice after intratracheal instillation of staphylococcal enterotoxin B. The POBN adducts detected by ESR were paralleled by infiltration of macrophages and neutrophils into the bronchoalveolar lavage fluid. To further investigate the mechanism of free radical generation, mice were pretreated with the macrophage toxicant gadolinium chloride, which significantly suppressed the radical generation. Free radical generation was also decreased by pretreatment with the xanthine oxidase (XO) inhibitor allopurinol, the iron chelator Desferal, and the inducible nitric oxide synthase (iNOS) inhibitor 1400W. Histopathologically, these drugs significantly reduced both the cell infiltration into the alveolar septal walls and the synthesis of pulmonary collagen fibers. Experiments with NADPH oxidase knockout mice showed that NADPH oxidase did not contribute to lipid radical generation. These results suggest that lipid-derived carbon-centered free radical production is important in the manifestation of IP and that a macrophage toxicant, an XO inhibitor, an iron chelator, and an iNOS inhibitor protect against both radical generation and the manifestation of IP.

An uneven expression of T cell receptor V genes in the arterial wall and peripheral blood in giant cell arteritis

The aim of the study was to investigate T cell receptor (TCR) usage at the time of diagnosis of giant cell arteritis (GCA) and to estimate the degree of clonality of T-cells infiltrating the lesion. Seven patients with biopsy-proven giant cell arteritis were included in the study. Immunocytochemistry in biopsies from the temporal arteries and flow cytometric analysis of peripheral blood lymphocytes (PBL) was performed using monoclonal antibodies specific for CD3, CD4 and CD8 and 13 TCR Valpha and Vbeta gene segment products. The CDR3 fragment length polymorphism was assessed by gel electrophoresis of PCR-amplified TCR segments. The T lymphocytes were found to be concentrated to the adventitia rather than the media or intima. Six of the seven patients with GCA had expansions of T lymphocytes, expressing selected TCR V genes in the arterial wall. None of these expansions was found in PBL. The infiltrating T-cells were poly- or oligoclonal. In conclusion, the dominating part of the inflammatory infiltrate in GCA emanates from the adventitial microvessels. There is an uneven expression of TCR V genes by T lymphocytes in the inflammatory infiltrates as compared to peripheral blood T lymphocytes at the time of diagnosis, consistent with an antigen-driven immunological reaction in the arterial wall.

Regulatory T cells modulate staphylococcal enterotoxin B-induced effector T-cell activation and acceleration of colitis

Oral administration of bacterial superantigen Staphylococcus aureus enterotoxin B (SEB) activates mucosal T cells but does not cause mucosal inflammation. We examined the effect of oral SEB on the development of mucosal inflammation in mice in the absence of regulatory T (Treg) cells. SCID mice were fed SEB 3 and 7 days after reconstitution with CD4(+) CD45RB(high) or CD4(+) CD45RB(high) plus CD4(+) CD45RB(low) T cells. Mice were sacrificed at different time points to examine changes in tissue damage and in T-cell phenotypes. Feeding SEB failed to produce any clinical effect on SCID mice reconstituted with CD4(+) CD45RB(high) and CD4(+) CD45RB(low) T cells, but feeding SEB accelerated the development of colitis in SCID mice reconstituted with CD4(+) CD45RB(high) T cells alone. The latter was associated with an increase in the number of CD4(+) Vbeta8(+) T cells expressing CD69 and a significantly lower number of CD4(+) CD25(+) Foxp3(+) T cells. These changes were not observed in SCID mice reconstituted with both CD45RB(high) and CD45RB(low) T cells. In addition, SEB impaired the development of Treg cells in the SCID mice reconstituted with CD4(+) CD45RB(high) T cells alone but had no direct effect on Treg cells. In the absence of Treg cells, feeding SEB induced activation of mucosal T cells and accelerated the development of colitis. This suggests that Treg cells prevent SEB-induced mucosal inflammation through modulation of SEB-induced T-cell activation.

Evaluating human T cell receptor gene expression by PCR

This unit describes the use of PCR to characterize and quantify rearranged transcripts from specific T cell receptor variable gene families in human tissue and peripheral blood lymphocytes. The strategy outlined in this unit has been extensively used on different sources of human tissue including brain, spinal cord, and skeletal muscle. A protocol is provided to clone and sequence PCR-amplified cDNA transcripts to study the junctional diversity of the expressed genes. A support protocol describes a method for reverse transcribing total RNA to make the cDNA required by the other protocols.

The role of superantigens in the immunobiology of retroviruses

Murine mammary tumour viruses (MMTVs) are retroviruses that encode superantigens capable of stimulating T cells via superantigen-reactive T cell receptor V beta chains. MMTVs are transmitted to the suckling offspring via the milk. We have established that class II and B cell-deficient mice that were foster nursed by virus-secreting mice do not transfer infectious MMTVs to their offspring. No MMTV proviruses could be detected in the spleen and mammary tissue of these mice and there was no deletion of MMTV superantigen-reactive T cells. These results confirm that superantigen expression in the context of MHC class II molecules is required for MMTV transmission. We conclude that B cells are essential for the completion of the viral life cycle in vivo. This indicates that B cells are infected first and that viral amplification takes place only if infected B cells present the MMTV superantigen on their surface which, in turn, results in activation of T cells expressing the appropriate T cell receptor V beta chains. These activated T cells stimulate B cells which enables viral replication. Human T cells carry all the structural features required for an efficient response to murine retrovirally encoded superantigens. Superantigen-like stimulation of human T cells has been demonstrated in both infectious and autoimmune diseases. Human immunodeficiency virus may encode a superantigen but this has not been proven.

Staphylococcus aureus-superantigen decreases FKBP51 mRNA expression and cell-response to suppressive efficacy of a glucocorticoid in human peripheral blood mononuclear cells: possible implication of mitogen-activated protein kinase pathways

Glucocorticoids are commonly used for treatment of chronic inflammatory diseases, while a number of patients show insensitivity to glucocorticoid treatment. The molecular basis of these individual differences in glucocorticoid pharmacodynamics has little been taken into account. Here we focus on the implication of Staphylococcus aureus-producing superantigen, such as toxic shock syndrome toxin-1 (TSST-1), in the glucocorticoid sensitivity of human peripheral blood mononuclear cells and cell-response to glucocorticoid to produce a transcript for FK506-binding protein (FKBP51). Peripheral blood mononuclear cell-sensitivity to glucocorticoid was assessed by a cell proliferation test. FKBP51mRNA expressions were determined by real-time reverse transcription-polymerase chain reaction (RT-PCR). We also compared concentrations of various cytokines produced in culture supernatant between concanavalin A- and TSST-1-stimulated peripheral blood mononuclear cells using a cytometric beads array. Mitogen-activated protein kinase (MAPK) phosphorylation activity in peripheral blood mononuclear cells stimulated with concanavalin A and TSST-1 was analyzed by a cell-based ELISA. Prednisolone markedly inhibited concanavalin A-induced peripheral blood mononuclear cell proliferation, but they scarcely inhibited TSST-1-induced peripheral blood mononuclear cell proliferation. The mean (S.D.) of immunosuppressant concentrations that would give 50% (IC(50)) values for prednisolone in concanavalin A-stimulated peripheral blood mononuclear cells was 52.6 (54.2) ng/ml, which was significantly lower than that in TSST-1-stimulated peripheral blood mononuclear cells, i.e., 574.2 (817.0) ng/ml (P<0.001). TSST-1-stimulated peripheral blood mononuclear cells for 48 h attenuated prednisolone-induced FKBP51mRNA expressions concomitantly with decreased sensitivity to the anti-proliferative effects of prednisolone. Concentrations of interleukin-2 (IL-2) produced from TSST-1-stimulated peripheral blood mononuclear cells were significantly higher than that from peripheral blood mononuclear cells stimulated with concanavalin A (P<0.0001). Both concanavalin A and TSST-1 enhanced the phosphorylation of extracellular signal-regulated kinase (ERK) and p38, whereas the level of c-jun terminal kinase (JNK) phosphorylation was only increased by TSST-1-stimulation in peripheral blood mononuclear cells. Furthermore, the decreased FKBP51mRNA by TSST-1was found to be recovered by JNK and mitogen-activated protein kinase (MEK)/ERK inhibitors. Our data suggest that TSST-1 reduces activity of glucocorticoid in peripheral blood mononuclear cells by JNK activation and subsequent production of IL-2. Therefore, JNK might be an attractive target for overcoming glucocorticoid insensitivity induced by TSST-1 in peripheral blood mononuclear cells.

Aggravation of bronchial eosinophilia in mice by nasal and bronchial exposure to Staphylococcus aureus enterotoxin B

BACKGROUND

The role of bacterial enterotoxins like Staphylococcus aureus enterotoxin B (SEB) in allergic asthma remains unknown. We used a mouse model of airway allergy to study the effects of nasal or bronchial contact with SEB on bronchial allergic inflammation.

METHODS

The features of allergic asthma were induced in ovalbumin (OVA)-sensitized mice (days 1-13) by repeated exposures to nebulized OVA (days 33-37). Nasal or bronchial application of SEB was performed on three occasions (days 33-35-37), and the effects on bronchial inflammation, IgE titres and expression levels of mRNA for T helper type 2 cytokines and other inflammatory mediators were evaluated.

RESULTS

Both nasal and bronchial SEB enhanced the allergen-induced bronchial inflammation, as reflected by more eosinophilic inflammation in the airway lumen and in bronchial tissue. Aggravation of experimental asthma correlated with higher expression of mRNA for IL-5, IL-4, IFN-gamma, IL-12 p40, eotaxin-1 and TGF-beta in bronchi. In addition, nasal SEB elevated concentrations of IL-4, IL-5 and IFN-gamma in serum and bronchial SEB increased titres of OVA-specific and total IgE in serum.

CONCLUSION

Our data illustrate the potential of both nasal as well as bronchial SEB to aggravate several features of allergic asthma in a mouse model.

The Role of Immune Response to Staphylococcus aureus Superantigens and Disease Severity in Relation to the Sensitivity to Tacrolimus in Atopic Dermatitis

BACKGROUND

Staphylococcus aureus-producing superantigens (SAgs), such as staphylococcal enterotoxin B (SEB) or toxic shock syndrome toxin-1 (TSST-1), are frequently observed in atopic dermatitis (AD). However, little has been done to establish the association of immune responses to SAgs and the therapeutic response to immunosuppressive drugs in AD. Therefore, we investigated the prevalence and role of SAgs in the pathophysiology and immunosuppressive drug sensitivity in AD patients.

METHODS

We classified 29 patients into two groups on the basis of their clinical AD scores: a low-score group (n = 14) corresponding to mild to moderate patients and a high-score group (n = 15) corresponding to severe patients. We estimated the plasma anti-SEB or TSST-1 IgE of these patients and healthy subjects by ELISA. We also estimated individual drug sensitivity by determining drug concentrations that would give 50% inhibition (IC(50)) of peripheral-blood mononuclear cell (PBMC) proliferation in vitro.

RESULTS

The levels of plasma anti-SEB or TSST-1 IgE in the severe patients were significantly higher than those in the mild to moderate patients (p < 0.05 and p < 0.01, respectively). When stimulated with concanavalin A in vitro, PBMCs in the severe patients exhibited low sensitivity to the suppressive efficacy of tacrolimus (FK506) as compared to the mild to moderate patients (p < 0.01). Furthermore, there was a significant correlation between the IC(50)s of FK506 and plasma anti-TSST-1 IgE levels (p < 0.01).

CONCLUSIONS

We showed that PBMCs in severe AD patients exhibited lower sensitivity to FK506, and had higher plasma levels of anti-TSST-1 IgE as compared to the mild AD patients. SAgs appear to be one of the causes of decreased PBMC sensitivity to FK506, and therefore an alternative treatment would be useful based on the individual drug sensitivity data and anti-TSST-1 IgE levels.

Allergic fungal sinusitis

Many common chronic inflammatory rhinosinusitis conditions (hypertrophic sinus disease [HSD]) have the histopathological profile of allergic or asthmatic inflammation. Allergic fungal sinusitis (AFS) is both a type of noninvasive fungal rhinosinusitis and a type of HSD. AFS has clinicopathological features that make it similar, but not identical, to allergic bronchopulmonary aspergillosis (ABPA). Allergic mucin is a defined pathological entity occurring in ABPA, AFS, and in the HSD "eosinophilic mucin rhinosinusitis (EMRS)." Diagnosis of AFS requires a careful review of surgical reports, histopathology, and culture results. Treatment includes surgery and aggressive postoperative medical management of allergic inflammatory disease. Prognosis is good with integrated medical-surgical follow-up, but recurrence remains problematic. The association of ABPA, AFS, and HSD with class II genes of the major histocompatibility complex places the initiation of these inflammatory diseases within the context of antigen presentation and the acquired immune response. Pathological immunomanipulation of this response by local microbial superantigens may be a common mechanism for disease pathogenesis. Future research into the molecular biology of these related conditions may offer insight into the pathogenesis of other chronic inflammatory diseases.

Allergic fungal sinusitis

Many common chronic inflammatory rhinosinusitis conditions (hypertrophic sinus disease [HSD]) have the histopathological profile of allergic or asthmatic inflammation. Allergic fungal sinusitis (AFS) is both a type of noninvasive fungal rhinosinusitis and a type of HSD. AFS has clinicopathological features that make it similar, but not identical, to allergic bronchopulmonary aspergillosis (ABPA). Allergic mucin is a defined pathological entity occurring in ABPA, AFS, and in the HSD "eosinophilic mucin rhinosinusitis (EMRS)." Diagnosis of AFS requires a careful review of surgical reports, histopathology, and culture results. Treatment includes surgery and aggressive postoperative medical management of allergic inflammatory disease. Prognosis is good with integrated medical-surgical follow-up, but recurrence remains problematic. The association of ABPA, AFS, and HSD with class II genes of the major histocompatibility complex places the initiation of these inflammatory diseases within the context of antigen presentation and the acquired immune response. Pathological immunomanipulation of this response by local microbial superantigens may be a common mechanism for disease pathogenesis. Future research into the molecular biology of these related conditions may offer insight into the pathogenesis of other chronic inflammatory diseases.

Crystal structures of T cell receptor (beta) chains related to rheumatoid arthritis

The crystal structures of the Vbeta17+ beta chains of two human T cell receptors (TCRs), originally derived from the synovial fluid (SF4) and tissue (C5-1) of a patient with rheumatoid arthritis (RA), have been determined in native (SF4) and mutant (C5-1(F104-->Y/C187-->S)) forms, respectively. These TCR beta chains form homo-dimers in solution and in crystals. Structural comparison reveals that the main-chain conformations in the CDR regions of the C5-1 and SF4 Vbeta17 closely resemble those of a Vbeta17 JM22 in a bound form; however, the CDR3 region shows different conformations among these three Vbeta17 structures. At the side-chain level, conformational differences were observed at the CDR2 regions between our two ligand-free forms and the bound JM22 form. Other significant differences were observed at the Vbeta regions 8-12, 40-44, and 82-88 between C5-1/SF4 and JM22 Vbeta17, implying that there is considerable variability in the structures of very similar beta chains. Structural alignments also reveal a considerable variation in the Vbeta-Cbeta associations, and this may affect ligand recognition. The crystal structures also provide insights into the structure basis of T cell recognition of Mycoplasma arthritidis mitogen (MAM), a superantigen that may be implicated in the development of human RA. Structural comparisons of the Vbeta domains of known TCR structures indicate that there are significant similarities among Vbeta regions that are MAM-reactive, whereas there appear to be significant structural differences among those Vbeta regions that lack MAM-reactivity. It further reveals that CDR2 and framework region (FR) 3 are likely to account for the binding of TCR to MAM.

Skewed T-cell receptor BV14 and BV16 expression and shared CDR3 sequence and common sequence motifs in synovial T cells of rheumatoid arthritis

T-lymphocytes play an important role in rheumatoid arthritis (RA). In this study, we evaluated the hypothesis that common T-cell receptor (TCR) structural features may exist among infiltrating T cells of different RA patients, if the TCR repertoire is shaped by interaction with common self or microbial antigens in the context of susceptible HLA genes in RA. Synovial lesion tissue (ST), synovial fluid (SF) and blood specimens from RA patients and controls were analyzed for TCR V gene repertoire by real-time PCR. There was highly skewed BV14 and BV16 usage in synovial T cells of RA as opposed to those of controls, which was accompanied with a trend for correlation between skewed BV16 and DRB1(*)0405. Immunoscope analysis of the V-D-J region of ST-derived T cells demonstrated oligoclonal and polyclonal expansion of BV14(+) and BV16(+) T cells. Detailed characterization using specific BV and BJ primers further revealed common clonotypes combining the same BV14/BV16, BJ and CDR3 length. DNA cloning and sequence analysis of the clonotypes confirmed identical CDR3 sequences and common CDR3 sequence motifs among different RA patients. The findings are important in the understanding of BV gene skewing and CDR3 structural characteristics among synovial infiltrating T cells of RA.

Immunization of volunteers with Salmonella enterica serovar Typhi strain Ty21a elicits the oligoclonal expansion of CD8+ T cells with predominant Vbeta repertoires

CD8(+) T cells are likely to play an important role in host defense against Salmonella enterica serovar Typhi by several effector mechanisms, including lysis of infected cells (cytotoxicity) and gamma interferon (IFN-gamma) secretion. In an effort to better understand these responses, we studied the T-cell receptor (TCR) repertoire of serovar Typhi-specific CD8(+) T cells in humans. To this end, we determined the TCR beta chain (Vbeta) usage of CD8(+) T cells from three volunteers orally immunized with Ty21a typhoid vaccine by flow cytometry using a panel of monoclonal antibodies. Although TCR Vbeta usage varied among volunteers, we identified oligoclonal Vbeta subset expansions in individual volunteers (Vbeta 2, 5.1, 8, 17, and 22 in volunteer 1; Vbeta 1, 2, 5.1, 14, 17, and 22 in volunteer 2; and Vbeta 3, 8, 14, and 16 in volunteer 3). These subsets were antigen specific, as shown by cytotoxicity and IFN-gamma secretion assays on Vbeta sorted cells and on T-cell clones derived from these volunteers. Moreover, eight-color flow cytometric analysis showed that these clones exhibited a T effector memory phenotype (i.e., CCR7(-) CD27(-) CD45RO(+) CD62L(-)) and coexpressed gut homing molecules (e.g., high levels of integrin alpha4beta7, intermediate levels of CCR9, and low levels of CD103). In conclusion, our results show that long-term T-cell responses to serovar Typhi in Ty21a vaccinees are oligoclonal, involving multiple TCR Vbeta families. Moreover, these serovar Typhi-specific CD8(+) T cells bearing defined Vbeta specificities are phenotypically and functionally consistent with T effector memory cells with preferential gut homing potential.

Human endogenous retroviruses: transposable elements with potential?

Human endogenous retroviruses (HERVs) are a significant component of a wider family of retroelements that constitute part of the human genome. These viruses, perhaps representative of previous exogenous retroviral infection, have been integrated and passed through successive generations within the germ line. The retention of HERVs and isolated elements, such as long-terminal repeats, could have the potential to harm. In this review we describe HERVs within the context of the family of known transposable elements and survey these viruses in terms of superantigens and molecular mimics. It is entirely possible that these mechanisms provide the potential for undesired immune responses.

Allergic fungal sinusitis

AFS is an increasingly recognized form of HSD, now reported throughout the world. It is probably the most frequently occurring fungal rhinosinusitis disorder. The term fungal sinusitis is no longer appropriate because the five categories of fungal rhinosinusitis can now be differentiated. Each category of fungal rhinosinusitis disorder carries different treatment approaches and prognosis. Diagnostic error can be minimized by adhering to strict diagnostic criteria. The analogy (but not identity) of AFS to ABPA has been supported by histopathology, immunopathology, and the clinical response to OCS treatment. AFS represents a true medical surgical disorder in which both surgery and postoperative medical treatment, if properly coordinated between medical and surgical specialists, leads to the best patient outcomes. Continued advances in the understanding of the immunogenetics and immunopathogenesis of AFS may provide fundamental insights into molecular mechanisms operant in other chronic inflammatory disorders, including other chronic eosinophilic-lymphocytic respiratory mucosal disorders such as common forms of HSD and chronic severe asthma.

Microbial superantigens induce glucocorticoid receptor beta and steroid resistance in a nasal explant model

OBJECTIVE

To study the role of superantigen (SAg) in inducing glucocorticoid (GC) receptor beta and steroid resistance in an explant model of nasal tissue.

METHODS

Nasal tissue was obtained from inferior turbinates of controls and ragweed (RW)-sensitive patients. Tissue samples were incubated with SAg of staphylococcal enterotoxin B. In addition, tissue samples from RW-sensitive patients were incubated with RW allergen in the presence and absence of both SAg and dexamethasone (DEX). The expression of GC receptor beta was assessed by immunocytochemistry. The expression of interleukin (IL)-2 and IL-4 mRNA was assessed by in situ hybridization.

RESULTS

SAg induced an increase in the expression of GC receptor beta in atopic tissue and to a lesser extent in nonatopic tissue. The most significant induction of GC receptor beta was observed in response to SAg and RW in atopic tissue. Stimulation of atopic tissue with RW alone and SAg alone induced IL-4 and IL-2 mRNA, respectively. Incubation of atopic tissue with both SAg and RW induced both IL-2 and IL-4 mRNA. The increase in IL-4 mRNA expression was blunted by the addition of DEX to atopic tissue stimulated with RW alone but not to tissue stimulated by both RW and SAg.

CONCLUSION

Our results demonstrate that SAgs induce steroid resistance in atopic nasal explant tissue by up-regulating the expression of GC receptor beta. Furthermore, we have shown that the up-regulation of GC receptor beta is a local event that is associated with the coexpression of IL-2 and IL-4 mRNA.

Chronic sinusitis: defective T-cells responding to superantigens, treated by reduction of fungi in the nose and air

In this study, the author used endoscopic sinus photography to study the effects of reduction of fungi in the nose, and in environmental air, on the sinus mucosa of 639 patients diagnosed with chronic rhinosinusitis. Sinus mucosal photographs were taken before and after reduction of fungal load in the nose and air, to determine if there was an optimum environmental air fungal load associated with sinus mucosal recovery to normal appearance. Systemic symptoms associated with fungal exposure, which resolved when fungus was removed from the patient and the environmental air and reappeared with recurrent environmental fungal exposure, are also discussed and are termed systemic fungal symptoms. Interventions consisted of nasal fungal load reduction with normal saline nasal irrigations and antimicrobial nasal sprays, and environmental air fungal load reduction with high-efficiency particulate air (HEPA) filtration in combination with ionizers or evaporation of a solution of botanical extract. Main outcome measures were obtained with environmental air 1-hr gravity-plate fungal colony counts, laser air particle counts, and endoscopic sinus photography. Blood levels of immunoglobulins IgG and IgE for 7 common molds were also determined. After intervention, 94% of patients who used antimicrobial nasal sprays and who reduced their environmental fungal air count to 0-4 colonies per 1-hr agar gravity-plate exposure (n = 365) exhibited normal sinus mucosa by endoscopic exam. Environmental air fungal counts that exceeded 4 colonies resulted in sinus mucosal abnormalities ranging from edema, to pus and/or nasal polyps at higher counts. Neutralization of allergy, and/or surgery, were used as appropriate following implementation of environmental measures. On the basis of these observations, as well as detailed clinical experience and a review of the current literature, the author hypothesizes that the pathogenesis of chronic rhinosinusitis, allergic fungal sinusitis, and systemic fungal symptoms is a genetic defect at the variable beta chain helper T-cell receptor (TCR Vbeta) site which requires the presence of an antigen (fungus). Chronic sinusitis patients who have recurring exposure to environmental air that contains fungal concentrations in excess of 4 colonies per 1-hr agar plate exposure appear to have an increased risk of persistent chronic sinusitis and/or systemic symptoms, regardless of the medical treatment provided.

The usefulness and the limitations of animal models in identifying targets for therapy in arthritis

Animal models have played a critical role in the history of modern drug development for rheumatoid arthritis (RA). In this chapter I examine the contributions of animal models in arthritis therapy from adjuvant arthritis and COX-1 inhibitors to transgenic mice and biological response modifiers. Advances in knowledge of the mechanisms of connective tissue disease are frequently derived from the study of animal models, and these findings frequently identify therapeutic targets that are subsequently evaluated in animal models. Hence a critical relationship between insights into the pathology of arthritis and the development of novel therapeutic approaches exists around the study of animal models of arthritis. In particular, we examine how the study of collagen-induced arthritis in rodents led to pioneering work in cytokine inhibitors for the successful therapy of RA.

Immunotherapy in Collagen-Induced Arthritis: Past, Present, and Future

Type II collagen-induced arthritis has played a critical role in the development of novel approaches to the treatment of rheumatoid arthritis. The model has provided insights into autoimmune mechanisms relevant to the pathogenesis of joint disease and permitted the identification of potential targets for arthritis therapy. Notably, the model excelled in the development of cytokine inhibition for rheumatoid arthritis, with investigations demonstrating that a complex network of cytokine interactions regulate the autoimmune response to collagen. Recent studies of collagen-induced arthritis provide indications of novel approaches to disease intervention. New directions include modulation of the recognition and presentation of autoantigens, inhibition of specific T cell subsets responding to autoantigens, blocking of stimulatory cosignals at the cell surface, decoys for cytoplasmic and nuclear activation signals, interference with lymphocyte migration to the synovial joint, and reduction of the mediators of joint destruction. These approaches can be implemented through gene therapy, biological response mediators, or classic pharmacological intervention.

Selective T cell receptor decrease in peripheral blood T lymphocytes of patients with polymyalgia rheumatica and giant cell arteritis

OBJECTIVES

To investigate the phenotype and T cell receptor (TCR) use in peripheral blood T cells in patients with polymyalgia rheumatica (PMR) and giant cell arteritis (GCA).

METHODS

Circulating T lymphocyte phenotype and TCR repertoire were studied by flow cytometry using specific monoclonal antibodies in 23 healthy controls and 37 patients with PMR/GCA.

RESULTS

Patients with active PMR/GCA showed an inverse relation between naive and memory CD4+ T cells and unchanged expression of activation surface markers compared with controls. CD4+ TCR BV expansions were seen in 12 (52%) controls and in 8 (22%) patients with active disease (p = 0.03). Within the CD8+ subset, the frequency of expansions was similar between groups. Most T cell expansions remained stable over time. Seventeen of the 23 patients with active PMR/GCA disclosed a simultaneous CD4+ and CD8+ T cell depletion for at least one particular BV family with a clear predominance of BV5S2/S3.

CONCLUSIONS

The phenotype of circulating T cells in patients with PMR/GCA is similar to that found in aged healthy subjects, except for the surface markers of naive and memory cells and a striking non-activated phenotype. Specific BV expansions in CD4+ and CD8+ T cells, which remain stable over time, are frequent in aged subjects, including patients with PMR/GCA. TCR BV changes in patients with active disease seem to be also age related, except for the significant decrease in certain BV families in both CD4+ and CD8+ T cell subsets, which may favour the participation of a superantigen stimulation in PMR/GCA.

Analysis of two T-cell receptor BV gene segment polymorphisms in caucasoid Brazilian patients with rheumatoid arthritis

Considering the role of T-lymphocytes in rheumatoid arthritis (RA) and a possible involvement of the TCR in the pathology of this disease we analyzed allelic and genotypic frequencies of variants of two TCRBV gene segments (TCRBV3S1 and TCRBV18) in RA. A total of 95 caucasoid South Brazilian RA patients were genotyped for both TCRBV gene segment variants by restriction fragment length polymorphism preceded by PCR (PCR-RFLP) and the obtained frequencies were compared to those from healthy individuals. Allelic frequencies for the TCRBV3S1 gene segment were, respectively, for RA patients and controls, 0.447 and 0.545 (allele 1) and 0.553 and 0.455 (allele 2). Allelic frequencies for the TCRBV18 gene segment were, respectively, for RA patients and controls, 0.824 and 0.806 (allele 1) and 0.176 and 0.194 (allele 2). Neither allelic frequencies nor genotypic frequencies differ among RA and healthy individuals, suggesting that there is not a direct association among the TCRBV allelic variants studied and the development of RA and thus excluding the possibility of use of these gene segment polymorphisms as RA susceptibility markers.

Current perspective on the pathogenesis of Graves' disease and ophthalmopathy

Graves' disease (GD) is a very common autoimmune disorder of the thyroid in which stimulatory antibodies bind to the thyrotropin receptor and activate glandular function, resulting in hyperthyroidism. In addition, some patients with GD develop localized manifestations including ophthalmopathy (GO) and dermopathy. Since the cloning of the receptor cDNA, significant progress has been made in understanding the structure-function relationship of the receptor, which has been discussed in a number of earlier reviews. In this paper, we have focused our discussion on studies related to the molecular mechanisms of the disease pathogenesis and the development of animal models for GD. It has become apparent that multiple factors contribute to the etiology of GD, including host genetic as well as environmental factors. Studies in experimental animals indicate that GD is a slowly progressing disease that involves activation and recruitment of thyrotropin receptor-specific T and B cells. This activation eventually results in the production of stimulatory antibodies that can cause hyperthyroidism. Similarly, significant new insights have been gained in our understanding of GO that occurs in a subset of patients with GD. As in GD, both environmental and genetic factors play important roles in the development of GO. Although a number of putative ocular autoantigens have been identified, their role in the pathogenesis of GO awaits confirmation. Extensive analyses of orbital tissues obtained from patients with GO have provided a clearer understanding of the roles of T and B cells, cytokines and chemokines, and various ocular tissues including ocular muscles and fibroblasts. Equally impressive is the progress made in understanding why connective tissues of the orbit and the skin in GO are singled out for activation and undergo extensive remodeling. Results to date indicate that fibroblasts can act as sentinel cells and initiate lymphocyte recruitment and tissue remodeling. Moreover, these fibroblasts can be readily activated by Ig in the sera of patients with GD, suggesting a central role for them in the pathogenesis. Collectively, recent studies have led to a better understanding of the pathogenesis of GD and GO and have opened up potential new avenues for developing novel treatments for GD and GO.