Medullary epithelial cells of the human thymus express a highly diverse selection of tissue-specific genes colocalized in chromosomal clusters

Autoimmune regulator initiates the expression of promiscuous genes in thymic epithelial cells

The expression of peripheral antigens in the thymus, known as promiscuous gene expression, has been implicated in T cell tolerance and autoimmunity. Here we identified thymic epithelial cells (TECs) as the main cell type that expresses a diverse range of tissue-restricted antigens (TRAs). The TECs of a common autoimmune (non-obese diabetic [NOD]) mouse model express much lower levels of an autoimmune regulator (Aire) and TRAs than normal (Balb/c) TECs. Transfection of an Aire plasmid led to increased levels of TRA expression in cultured TECs from Balb/c and NOD mice; an increase that was enhanced by the presence of thymocytes. These data show that Aire initiates promiscuous gene expression in TECs, and that this function might be under thymocyte control.

Autoimmune Processes in the Central Nervous System

In this chapter we discuss the factors that contribute to the unique immunological environment of the central nervous system and the mechanisms that may account for the development of autoimmunity within the CNS, including infectious agents as inducers of autoimmune disease. Consideration is given to a variety of human neurological diseases of autoimmune or presumed autoimmune etiology: autism, neuromyelitis optica, neuromyotonia, schizophrenia, lethargic encephalitis and stiff‐man syndrome. Also, we discuss autoimmunity as a possible mediator of CNS repair and examples of the protective effects of bacterial and helminth infections on CNS disease. Multiple sclerosis and models of multiple sclerosis are discussed with special attention given to the Theiler's virus‐induced demyelination model.

Tolerance and autoimmunity: lessons at the bedside of primary immunodeficiencies

The recent progress in the genetic characterization of many primary immunodeficiencies (PIDs) allows for a better understanding of immune molecular and cellular mechanisms. The present chapter discusses associations between PIDs and autoimmune diseases (AIDs) in this new light. PIDs are classified according to the frequency of association with AIDs, defining four groups of conditions: systematic (more than 80% of all patients), strong (10-80%), mild (less than 10%), and absent (no available descriptions). Several general conclusions could be drawn: (1) pathological autoimmune (AI) manifestations are very frequently associated with PIDs, indicating that, contrary to conventional notions, antimicrobial protection and natural tolerance to body tissues share many basic mechanisms; (2) in some gene defects, association is so strong that one could speak of "monogenic" AIDs; (3) basic types of PIDs are selectively associated with AID of a particular set of target tissues; (4) while for some gene defects, current theory satisfactorily explains pathogenesis of the corresponding AID, other situations suggest extensive gaps in the present understanding of natural tolerance; and (5) not exceptionally, observations on the AI phenotype for the same gene defect in mouse and man are not concordant, perhaps owing to the limited genetic diversity of mouse models, often limited to a single mouse strain. Overall, clinical observations on PID support the new paradigm of "dominant" tolerance to self-components, in which AID owes to deficits in immune responses (i.e., in regulatory mechanisms), rather than from excessive reactivity.

An IRF8-binding promoter variant and AIRE control CHRNA1 promiscuous expression in thymus

Promiscuous expression of tissue-restricted auto-antigens in the thymus imposes T-cell tolerance and provides protection from autoimmune diseases. Promiscuous expression of a set of self-antigens occurs in medullary thymic epithelial cells and is partly controlled by the autoimmune regulator (AIRE), a nuclear protein for which loss-of-function mutations cause the type 1 autoimmune polyendocrine syndrome. However, additional factors must be involved in the regulation of this promiscuous expression. Here we describe a mechanism controlling thymic transcription of a prototypic tissue-restricted human auto-antigen gene, CHRNA1. This gene encodes the alpha-subunit of the muscle acetylcholine receptor, which is the main target of pathogenic auto-antibodies in autoimmune myasthenia gravis. On re-sequencing the CHRNA1 gene, we identified a functional bi-allelic variant in the promoter that is associated with early onset of disease in two independent human populations (France and United Kingdom). We show that this variant prevents binding of interferon regulatory factor 8 (IRF8) and abrogates CHRNA1 promoter activity in thymic epithelial cells in vitro. Notably, both the CHRNA1 promoter variant and AIRE modulate CHRNA1 messenger RNA levels in human medullary thymic epithelial cells ex vivo and also in a transactivation assay. These findings reveal a critical function of AIRE and the interferon signalling pathway in regulating quantitative expression of this auto-antigen in the thymus, suggesting that together they set the threshold for self-tolerance versus autoimmunity.

Prevention of autoimmune gastritis in mice requires extra-thymic T-cell deletion and suppression by regulatory T cells

BACKGROUND AND AIMS

Autoimmune gastritis is one of the most common autoimmune diseases and is caused by a CD4(+) T-cell response to the gastric H(+)/K(+) ATPase encoded by Atp4a and Atp4b (H(+)/K(+) ATPase). Here, we have elucidated events that result in immunological tolerance to the H(+)/K(+) ATPase and thus the prevention of autoimmune gastritis.

METHODS

T cells from H(+)/K(+) ATPase-deficient mice and H(+)/K(+) ATPase-specific T-cell receptor transgenic mice were purified and transferred to wild-type (WT) or H(+)/K(+) ATPase-deficient recipients to assess the impact of exposure to antigen on pathogenicity.

RESULTS

The CD4(+) T-cell population from H(+)/K(+) ATPase-deficient mice was highly effective at inducing gastritis when compared with T cells from WT mice and, as a population, was comparatively resistant to the suppressive activity of regulatory T cells. Exposing T cells from H(+)/K(+) ATPase-deficient mice to H(+)/K(+) ATPase in WT mice decreased their ability to induce gastritis and resulted in a population that could be more easily suppressed by T(reg) cells. Transfer of clonotypic antigen-inexperienced H(+)/K(+) ATPase-specific T cells into WT mice resulted in extra-thymic clonal deletion.

CONCLUSIONS

Prevention of autoimmune gastritis requires the extra-thymic purging of highly autoaggressive H(+)/K(+) ATPase-specific T cells to produce a T-cell repertoire that is more susceptible to the suppressive activity of regulatory T cells. Taken together with recent published data describing the role of T-cell receptor signalling in the maintenance of regulatory T-cell populations, we propose that exposure of T cells to antigen in the periphery is able to both delete autoaggressive specificities and maintain regulatory T-cell activity, establishing a balance between pathogenicity and regulation.

Lack of Reactive Oxygen Species Breaks T Cell Tolerance to Collagen Type II and Allows Development of Arthritis in Mice

The view on reactive oxygen species (ROS) in inflammation is currently shifting from being considered damaging toward having a more complex role in regulating inflammatory reactions. We recently demonstrated a role of ROS in regulation of animal models for the autoimmune disease rheumatoid arthritis. Low levels of ROS production, due to a mutation in the Ncf1 gene coding for the Ncf1 (alias p47(phox)) subunit of the NADPH oxidase complex, was shown to be associated with increased autoimmunity and arthritis severity in both rats and mice. To further investigate the role of ROS in autoimmunity, we studied transgenic mice expressing collagen type II (CII) with a mutation (D266E) in the immunodominant epitope that mimics the rat and human CII (i.e., mutated mouse collagen or MMC). This mutation results in a stronger binding of the epitope to the MHC class II molecule and leads to more pronounced tolerance and resistance to arthritis induced with rat CII. When the Ncf1 mutation was bred into these mice, tolerance was broken, resulting in enhanced T cell autoreactivity, high titers of anti-CII Abs, and development of severe arthritis. These findings highlight the importance of a sufficient ROS production in maintenance of tolerance to self-Ags, a central mechanism in autoimmune diseases such as rheumatoid arthritis. This is important as we, for the first time, can follow the effect of ROS on molecular mechanisms where T cells are responsible for either protection or promotion of arthritis depending on the level of oxygen species produced.

Deletional Self-Tolerance to a Melanocyte/Melanoma Antigen Derived from Tyrosinase Is Mediated by a Radio-Resistant Cell in Peripheral and Mesenteric Lymph Nodes

Self-tolerance to melanocyte differentiation Ags limits the ability to generate therapeutic antimelanoma responses. However, the mechanisms responsible for CD8 T cell tolerance to these Ags are unknown. We have used a newly generated TCR-transgenic mouse to establish the basis of tolerance to one such Ag from tyrosinase. Despite expression of tyrosinase transcripts in the thymus, central deletion does not shape the tyrosinase-specific CD8 T cell repertoire. We demonstrate that this endogenously expressed melanocyte Ag is constitutively presented in both peripheral and mesenteric lymph nodes, leading to abortive activation and deletion of tyrosinase-specific CD8 T cells. Importantly, this Ag is not presented by either radio-sensitive dendritic cells, or by radio-resistant Langerhans cells. Thus, for this endogenous Ag, cross-tolerization does not appear to be an operative mechanism. Instead, we find radioresistant tyrosinase mRNA expression in lymphoid compartments where CD8 T cell deletion occurs. This suggests that direct presentation of tyrosinase by radio-resistant lymph node resident cells is entirely responsible for tolerance to this endogenous melanocyte differentiation Ag.

What's new in the Aire?

Unraveling the mechanisms underlying autoimmune disease remains a difficult challenge. Recent lessons learned from the study of AIRE (autoimmune regulator), the gene responsible for the rare monogenic human syndrome APS-1, highlight the power of genetics to reveal disease pathogenesis. With the discovery of AIRE, central tolerance has re-emerged as a crucial check against autoimmunity. Aire-mediated regulation of diverse self-antigens in the thymus serves as a paradigm for the importance of promiscuous gene expression in the prevention of autoimmune disease. Recent characterization of Aire-targeted antigens continues to bear this out. Here, we review the current progress surrounding the role of Aire in central tolerance from a molecular, genetic and developmental basis.

Optimization of comparative expressed sequence hybridization for genome-wide expression profiling at chromosome level

Comparative expressed sequence hybridization (CESH) has recently been developed for global expression profiling at chromosome level. To improve its specificity and sensitivity, we examined the effects of cDNA amplification and labeling methods on CESH profiles, using a gastric cancer cell line, Kato III, and compared the CESH profiles to cDNA microarray and reverse transcriptase-polymerase chain reaction (RT-PCR) data. CESH results were scarcely affected by the amplification process, either at the RNA level with T7 polymerase or at the cDNA level with degenerate oligonucleotide-primed PCR (DOP-PCR). The labeling method, however, did remarkably affect the CESH results; false positive shifts of the test/reference ratio (T/R) were not detected in self-matched CESH with pre-cDNA labeling and random priming labeling of cDNA but were consistently seen with DOP-PCR labeling in 11 chromosomes. The use of cDNA deriving from mRNA either with pre-cDNA or random priming labeling gave results of higher detection sensitivity for regions of up- or downregulated expression and higher concordance with the microarray and RT-PCR data in the corresponding regions than with conventional CESH. This modification of CESH with random priming labeling was found feasible by its application to Kato III cells with and without 5-aza-2'-deoxycytidine treatment; the regions identified as epigenetically silenced included genes that were reportedly methylated in Kato III.

Expression of Tumor-Associated Differentiation Antigens, MUC1 Glycoforms and CEA, in Human Thymic Epithelial Cells: Implications for Self-Tolerance and Tumor Therapy

Expression of tissue-restricted self-antigens in the thymus, termed promiscuous gene expression, imposes T cell tolerance and protects from autoimmune diseases. This antigen pool also includes various types of tumor-associated antigens (TAA) previously thought to be secluded from the immune system. The scope of promiscuous gene expression has been defined by mRNA analysis at the global level of isolated medullary thymic epithelial cells (mTECs). Information at the protein level on the frequency of mTECs expressing a given antigen, on coexpression patterns, and post-translational modifications is largely missing. We report here promiscuous expression at the protein level of two TAA, MUC1 and CEA, in situ and in purified human mTECs. Both antigens are expressed in 1% to 3% of mTECs, either individually or coexpressed in the same cell. Using a panel of anti-MUC1 monoclonal antibodies recognizing different post-translational modifications, i.e., glycoforms of MUC1, we show that only fully glycosylated forms of MUC1 and the differentiation-dependent glycoforms were detected on mTECs, but not the cancer-associated glycoforms. Our findings imply that MUC1 and CEA are amenable to central tolerance induction, which might, however, be incomplete in case of tumor cell-restricted MUC1 glycoforms. Knowledge of these subtleties in promiscuous gene expression may, in the future, assist the selection of T cell tumor vaccines for clinical trials.

Highly variable expression of tissue-restricted self-antigens in human thymus: Implications for self-tolerance and autoimmunity

Induction of T cell tolerance in the thymus (central tolerance) is essential for preventing organ-specific autoimmunity. This apparent paradox is in part explained by promiscuous expression of numerous tissue-restricted self-antigens (TRA) in medullary thymic epithelial cells (mTEC), which is highly conserved between mice and man. In animal models, the threshold of central tolerance towards such TRA is surprisingly sensitive towards minor shifts in antigen expression levels and this might also be the case in humans. To precisely assess the inter-individual variability of TRA expression in man, we determined the level of transcription of several auto-antigens in purified human mTEC and subsets thereof by quantitative RT-PCR. We detected two expression patterns: first, high variability (>20-fold) correlated with autoimmune regulator (Aire) expression and mTEC differentiation, and secondly, non-correlated low variability. Importantly, our approach revealed a significantly higher Aire-correlated insulin transcription in mTEC of carriers of the protective insulin-dependent diabetes mellitus locus 2 haplotype compared to the non-protective haplotype. The considerable, yet selective variability in thymic expression levels of target auto-antigen expression might constitute a hitherto underestimated risk factor for the susceptibility of autoimmune diseases in man.

Should 'low-risk' thyroid cancer patients with residual thyroglobulin be re-treated with iodine 131?

OBJECTIVE

The American consensus statement on patients with low-risk thyroid cancer, published in 2003, suggests repeat (131)I therapy if the thyroglobulin value is elevated at first follow-up. We evaluated this strategy in our practice.

METHODS

Among 407 patients with thyroid cancer who had total thyroidectomy and (131)I ablation between January 2000 and December 2003, 12 patients with stage I thyroid cancer (any tumour (T), any node (N), metastasis (M)0 if < 45 years or T1, N0, M0 if > 45 years), were re-treated on the basis of their thyroglobulin level at first follow-up. Mean patient age was 32.8 years. None of them had a T4 tumour. Thyroglobulin levels after thyroid hormone withdrawal 'off-T4' ranged between 4.5 and 251 ng/ml (median 8). One to four courses of 3.7 GBq (131)I were given.

RESULTS

Three patients had a negative (131)I therapy scan and an uneventful course. Two patients had slight residual uptake only in the thyroid bed and negative ultrasound examination. Four patients had isolated (131)I uptake in the mediastinal region. No abnormalities were found on complementary mediastinal imaging. This finding was interpreted as benign (131)I thymic uptake. The last three patients also had mediastinal thymic uptake associated with a slight thyroid bed uptake. One patient had a gradual increase in the thyroglobulin level, and underwent resection of nonfunctioning neck lymph nodes. Thyroglobulin levels declined in all other patients.

CONCLUSIONS

No distant lesions were found in a group of young 'low-risk' thyroid cancer patients given empirical (131)I therapy for residual thyroglobulin. When blind (131)I therapy shows no uptake, or uptake limited to the thymus, (131)I therapy should not be repeated. The authors also briefly discuss the hypothesis that enhanced thymus might be a source of benign thyroglobulin secretion.

Cancer/testis antigen expression and specific cytotoxic T lymphocyte responses in non small cell lung cancer

Non small cell lung cancers (NSCLC) express cancer/testis antigens (CTA) genes and MAGE-A expression correlates with poor prognosis in squamous cell carcinomas. We addressed cytotoxic T lymphocytes (CTL) responses to HLA class I restricted CTA epitopes in TIL from NSCLC in an unselected group of 33 patients consecutively undergoing surgery. Expression of MAGE-A1, -A2, -A3, -A4, -A10, -A12 and NY-ESO-1 CTA genes was tested by quantitative RT-PCR. Monoclonal antibodies (MAb) recognizing MAGE-A and NY-ESO-1 CTA were used to detect CTA by immunohistochemistry. CD8(+) TIL obtained from tumors upon culture with anti CD3 and anti CD28 mAb and IL-2 were stimulated with autologous mature DC (mDC) and HLA-A*0101 restricted MAGE-A1(161-169) or MAGE-A3(168-176) peptides or HLA-A*0201 restricted MAGE-A4(230-239), MAGE-A10(254-262), NY-ESO-1(157-165) or multi-MAGE-A (YLEYRQVPV) peptides or a recombinant vaccinia virus (rVV) encoding MAGE-A and NY-ESO-1 HLA-A*0201 restricted epitopes and CD80 co-stimulatory molecule. Specificity was assessed by (51)Cr release and multimer staining. At least one CTA gene was expressed in tumors from 15/33 patients. In 10 specimens, at least 4 CTA genes were concomitantly expressed. These data were largely confirmed by immunohistochemistry. TIL were expanded from 26/33 specimens and CTA-specific CTL activity was detectable in 7/26 TIL. In 6, however, specific cytotoxicity was weak, (<40% lysis at a 50:1 E:T ratio) and multimer staining was undetectable. In one case, high (>60% lysis at 50:1 E:T ratio) MAGE-A10(254-262) specific, HLA-A*0201 restricted response was observed. Supportive evidence was provided by corresponding multimer staining. Although CTA genes are frequently expressed in NSCLC, detection of CTL reactivity against CTA epitopes in TIL from nonimmunized NSCLC patients represents a rare event.

Redirecting T lymphocyte specificity by T cell receptor gene transfer – A new era for immunotherapy

The therapeutic efficacy of adoptively transferred cytotoxic T lymphocytes (CTL) has been demonstrated in clinical trials for the treatment of chronic myelogenous leukemia, cytomegalovirus-mediated disease, and Epstein-Barr virus-positive B cell lymphomas. It is however limited by the difficulty of generating sufficient amounts of CTLs in vitro, especially for the treatment of solid tumors. Recent gene therapy approaches, including two clinical trials, successfully apply genetic engineering of T cell specificity by T cell receptor (TCR) gene transfer. In this review we want to elucidate several principles of the redirection of T cell specificity. We cover basic aspects of retroviral gene transfer, regarding transduction efficacy and transgene expression levels. It was demonstrated that the number of TCR molecules on a T cell is important for its function. Therefore, an efficient transfer system that yields high transduction efficiency and strong and stable transgene expression is a prerequisite to achieve effector function by redirected T cells. Furthermore, we consider more recent aspects of T cell specificity engineering. These include the possibility of co-transferring coreceptors to create for example functional T helper cells by engrafting CD4(+) T cells with a MHC class I restricted TCR and the CD8 coreceptor and vice versa. Also, risks related to the adoptive transfer of TCR gene-modified T cells and possible safety mechanisms are discussed. Finally, we summarize recent findings describing transferred TCRs capable of displacing endogenous TCRs from the cell surface.

Thymus organogenesis and development of the thymic stroma

T-cell development occurs principally in the thymus. Here, immature progenitor cells are guided through the differentiation and selection steps required to generate a complex T-cell repertoire that is both self-tolerant and has propensity to bind self major histocompatibility complex. These processes depend on an array of functionally distinct epithelial cell types within the thymic stroma, which have a common developmental origin in the pharyngeal endoderm. Here, we describe the structural and phenotypic attributes of the thymic stroma, and review current cellular and molecular understanding of thymus organogenesis.

Immune tolerance and control of CNS autoimmunity: from animal models to MS patients

Multiple sclerosis (MS) is a chronic inflammatory disease resulting in demyelination and axonal loss within the CNS. An autoimmune reaction directed against myelin antigens contributes to the disease process. As the CNS has long been considered an immune privileged site, how such an immune response can develop locally has remained enigmatic. Recent data, mostly based on the study of animal models for MS, have shown that the CNS is in fact more permissive to the development of immune responses than previously thought. This observation is counterbalanced by the fact that immune tolerance to myelin antigens can be induced outside the CNS. This review focuses on the mechanisms preventing CNS autoimmunity, which act in three separate tissues. In the thymus, expression of CNS autoantigens promotes partial protection, notably through elimination of autoreactive T cells. In the secondary lymphoid organs, the remaining autoreactive T cells are kept under control by the naturally occurring regulatory T cells of the CD4(+)Foxp3(+) phenotype. In the CNS, multiple mechanisms including the local activation of regulatory T cells further limit autoimmunity. A better understanding of the induction of regulatory T cells, of their mechanisms of action, and of approaches to manipulate them in vivo may offer new therapeutic opportunities for MS patients.

Systematic interpretation of microarray data using experiment annotations

BACKGROUND

Up to now, microarray data are mostly assessed in context with only one or few parameters characterizing the experimental conditions under study. More explicit experiment annotations, however, are highly useful for interpreting microarray data, when available in a statistically accessible format.

RESULTS

We provide means to preprocess these additional data, and to extract relevant traits corresponding to the transcription patterns under study. We found correspondence analysis particularly well-suited for mapping such extracted traits. It visualizes associations both among and between the traits, the hereby annotated experiments, and the genes, revealing how they are all interrelated. Here, we apply our methods to the systematic interpretation of radioactive (single channel) and two-channel data, stemming from model organisms such as yeast and drosophila up to complex human cancer samples. Inclusion of technical parameters allows for identification of artifacts and flaws in experimental design.

CONCLUSION

Biological and clinical traits can act as landmarks in transcription space, systematically mapping the variance of large datasets from the predominant changes down toward intricate details.

Thymus-Dependent T Cell Tolerance of Neuroendocrine Functions: Principles, Reflections, and Implications for Tolerogenic/Negative Self-Vaccination

Under the evolutionary pressure exerted by the emergence of adaptive immunity and its inherent risk of horror autotoxicus, the thymus appeared some 500 million years ago as a novel lymphoid structure able to prevent autoimmunity and to orchestrate self-tolerance as a cornerstone in the physiology of the immune system. Also, the thymus plays a prominent role in T cell education to neuroendocrine principles. Some self-antigens (oxytocin, neurotensin, insulin-like growth factor 2 [IGF-2]) have been selected to be predominantly expressed in thymic epithelium and to be presented to thymus T cells for educating them to tolerate other antigens related to them. In the insulin family, IGF2 is dominantly transcribed in cortical (c) and medullary (m) thymic epithelial cells (TECs), whereas the insulin gene (INS) is expressed at low level by only a few subsets of mTECs. Intrathymic transcription of both IGF2 and INS is under the control of the autoimmune regulator (Aire) gene. The highest concentrations of IGF-2 in the thymus explain why this peptide is much more tolerated than insulin, and why tolerance to IGF-2 is so difficult to break by active immunization. The high level of tolerance to IGF-2 is correlated to the development of a tolerogenic/regulatory profile when the sequence B11-25 of IGF-2 (homologous to the autoantigen insulin B9-23) is presented to DQ8+ type 1 diabetic patients. Since subcutaneous and oral insulin does not exert any tolerogenic properties, IGF-2 and other thymus self-antigens related to type 1 diabetes (T1D) should be preferred to insulin for the design of novel specific antigen-based preventive approaches against T1D.

NF-kappaB2 is required for the establishment of central tolerance through an Aire-dependent pathway

NF-kappaB2-deficient mice have impaired T and B cell responses. We found, however, that in these mice there was severe infiltration of lymphocytes into multiple organs and increased activity of autoantibodies to peripheral tissue antigens in a manner similar to that of autoimmune regulator-deficient (Aire-deficient) mice. We further demonstrated that NF-kappaB2 was required for thymic Aire gene transcriptional regulation. The Nfkb2(-/-) thymus had distinct cortical and medullar structures, but reduced Aire and target gene expression of peripheral tissue antigens. Engraftment of Nfkb2(-/-) thymic stroma to nude mice recapitulated the autoimmune phenotype of the native Nfkb2(-/-) mice, confirming a key defect in central tolerance. Lymphotoxin beta receptor (LTbetaR) ligation-induced Aire gene expression was also largely abolished in the absence of NF-kappaB2. Thus NF-kappaB2 downstream of LTbetaR plays an important role in the regulation of central tolerance in an Aire-dependent manner.

NY-ESO-1: review of an immunogenic tumor antigen

In the 9 years since its discovery, cancer-testis antigen NY-ESO-1 has made one of the fastest transitions from molecular, cellular, and immunological description to vaccine and immunotherapy candidate, already tested in various formulations in more than 30 clinical trials worldwide. Its main characteristic resides in its capacity to elicit spontaneous antibody and T-cell responses in a proportion of cancer patients. An overview of immunological findings and immunotherapeutic approaches with NY-ESO-1, as well the role of regulation in NY-ESO-1 immunogenicity, is presented here.

Ets transcription factors regulate AIRE gene promoter

Autoimmune regulator (AIRE) directs the expression of self-antigens in thymus. Defects in AIRE gene cause an organ-specific autoimmune disease called autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED). AIRE protein is mainly expressed in thymic medullary epithelial cells, thus implying a strict control over its expression pattern. To date, only limited information is available on mechanisms responsible for the regulation of AIRE gene. Here, we show that Ets transcription factor family members Ets-1, Ets-2, and ESE-1 have positive effect on AIRE transcription. Site-directed mutagenesis and transfection studies revealed that two of the three Ets binding sites in AIRE promoter are functional and this finding has been confirmed by the electrophoretic mobility shift assay. The AIRE promoter activity could be stimulated by phorbol myristate acetate (PMA) and this activation was further enhanced by Ets transcription factors. Our results demonstrate for the first time that AIRE gene is a downstream target for the Ets family of transcription factors.

Cancer immunotherapy and preclinical studies: why we are not wasting our time with animal experiments

Experimental research on the immune response to transplanted tumors has led to pioneering discoveries that laid many of the foundations for the current field of immunology. Experimental research in oncology has proven that murine and human tumors have antigens that are truly cancer specific. This article discusses research investigating how can antigens on cancer cells be used to help eradicate cancer.

Isolation and characterization of proinsulin-producing medullary thymic epithelial cell clones

Proinsulin, like many tissue-specific antigens, is expressed by rare (1-3%) cells of the thymus medullary stroma, presumably for the purpose of self-tolerance. Levels of this expression are associated with type 1 diabetes susceptibility in humans and in the NOD mouse. To further understand the mechanism of central tolerance induction by these rare cells, we have isolated and cultured two proinsulin-producing epithelial cell clones from murine thymus. These cells have a typical epithelial morphology and, by flow cytometry, a surface phenotype representative of mature thymic medullary epithelial cells (G8.8(+)/UEA-1(+)/DEC205(-)/CD45(-)/MHC II(+)). By RT-PCR, they express predominantly Ins2 as opposed to Ins1, as does whole thymus. Expression of the transcription factor Aire, implicated in enhancing promiscuous thymic expression of tissue-specific antigens, fell to very low levels after a few passages but increased 20-fold upon exposure to an agonistic anti-lymphotoxin B antibody, concurrent with 2.5-fold enhanced insulin expression. RNA of Pdx-1, Glut-2, and Gck was detectable by RT-PCR in whole thymus but not in the clones, suggesting thymic proinsulin expression is Pdx-1 independent and that Pdx-1, Glut-2, and Gck are likely expressed in the thymus as antigens, not as regulatory molecules.

Expression profiling of autoimmune regulator AIRE mRNA in a comprehensive set of human normal and neoplastic tissues

Defects in the autoimmune regulator (AIRE) gene cause the monogenic autoimmune disease autoimmune polyendocrinopathy syndrome type 1 (APS-1), which is characterized by a loss of self-tolerance to multiple organs. In concordance with its role in immune tolerance, AIRE is strongly expressed in medullary thymic epithelial cells (mTECs). Data on mechanisms controlling AIRE activation and the expression of this gene in other tissues are fragmentary and controversial. We report here AIRE mRNA expression profiling of a large set of normal human tissues and cells, tumor specimen and methylation deficient cell lines. On this broad data basis we found that AIRE mRNA expression is confined to mTECs in thymus and to lymph node tissue and that DNA hypomethylation contributes to transcriptional control of this gene.

Onset of promiscuous gene expression in murine fetal thymus organ culture

T-cell differentiation and induction of tolerance to self-antigens occurs mainly in the thymus. Thymic stromal cells, specifically medullary thymic epithelial cells, express a diverse set of genes encoding parenchymal organ-specific proteins. This phenomenon has been termed promiscuous gene expression (PGE) and has been implicated in preventing organ-specific autoimmunity by inducing T-cell tolerance to self antigens. Early thymopoiesis and the critical factors involved in T-cell differentiation can be reproduced in vitro by murine fetal thymus organ culture (FTOC), which mimics the natural thymic microenvironment. To evaluate the occurrence of PGE in FTOC, gene expression profiling during in vitro thymic development in BALB/c mice was performed using a set of nylon cDNA microarrays containing 9216 sequences. The statistical analysis of the microarray data (sam program) revealed the temporal repression and induction of 57 parenchymal and seven lymphoid organ-specific genes. Most of the genes analysed are repressed during early thymic development (15-17 days post-coitum). The expression of the autoimmune regulator (AIRE) gene at 16 days post-coitum marks the onset of PGE. This precedes the induction of parenchymal organ genes during the late developmental phase at 20 days post-coitum. The mechanism of T-cell tolerance induction begins during fetal development and continues into adulthood. Our findings are significant because they show a fine demarcation of PGE onset, which plays a central role in induction of T-cell tolerance.

Tolerance to proinsulin-2 is due to radioresistant thymic cells

Proinsulin is a key Ag in type 1 diabetes, but the mechanisms regulating proinsulin immune tolerance are unknown. We have shown that preproinsulin-2 gene-deficient mice (proins-2(-/-)) are intolerant to proinsulin-2. In this study, we analyzed the mechanisms underlying T cell-mediated tolerance to proinsulin-2 in 129/Sv nonautoimmune mice. The expression of one proinsulin-2 allele, whatever its parental origin, was sufficient to maintain tolerance. The site of proinsulin-2 expression relevant to tolerance was evaluated in thymus and bone marrow chimeras. CD4+ T cell reactivity to proinsulin-2 was independent of proinsulin-2 expression in radiation-sensitive bone marrow-derived cells. A wt thymus restored tolerance in proins-2(-/-) mice. Conversely, the absence of the preproinsulin-2 gene in radioresistant thymic cells was sufficient to break tolerance. Although chimeric animals had proinsulin-2-reactive CD4+ T cells in their peripheral repertoire, they displayed no insulitis or insulin Abs, suggesting additional protective mechanisms. In a model involving transfer to immunodeficient (CD3epsilon(-/-)) mice, naive and proinsulin-2-primed CD4+ T cells were not activated, but could be activated by immunization regardless of whether the recipient mice expressed proinsulin-2. Furthermore, we could not identify a role for putative specific T cells regulating proinsulin-2-reactive CD4+ T in transfer experiments. Thus, proinsulin-2 gene expression by radioresistant thymic epithelial cells is involved in the induction of self-tolerance, and additional factors are required to induce islet abnormalities.

Directions in the immune targeting of cancer: lessons learned from the cancer-testis Ag NY-ESO-1

Since the early 1990s, numerous cancer Ag have been defined and for a handful of these there is now some clinical experience, which has made it possible to assess their value as targets for cancer immunotherapy. The cancer-testis Ag have been particularly attractive because their expression is limited to cancer and virtually no non-malignant cells apart from germ cells and trophoblast. Among these, NY-ESO-1 has been the focus of our attention. The exceptional immunogenicity of this Ag coupled with its widespread distribution among many cancer types make it a very good vaccine candidate, with the potential to be used in vaccines against many types of malignancies. This article reviews emerging knowledge about the biology of NY-ESO-1 and experience with the early clinical development of vaccines directed against NY-ESO-1. These early studies have yielded a wealth of information about the immunology of NY-ESO-1 and set the scene for future clinical strategies for immune targeting of cancer.

Lymphotoxin pathway-directed, autoimmune regulator-independent central tolerance to arthritogenic collagen

Ectopic expression of peripherally restricted Ags by medullary thymic epithelial cells (mTECs) is associated with negative selection. Autoimmune regulator (AIRE) is considered to be the master regulator of these Ags. We show in this study that the ectopic expression of type II collagen (CII) in mTECs and the corresponding central tolerance to CII are AIRE independent but lymphotoxin dependent. The failure to properly express CII in mTECs of Lta(-/-) and Ltbr(-/-) mice leads to overt autoimmunity to CII and exquisite susceptibility to arthritis. These findings define the existence of additional pathways of ectopic peripheral Ag expression, parallel to and independent of AIRE, which may cover an extended spectrum of peripheral Ags in the thymus.

Autoimmunity: basic mechanisms and implications in endocrine diseases. Part I

Autoimmunity implies disturbances at several levels of the immune control. Self-tolerance and discrimination between self and non-self synergize to avoid the development of autoimmunity. Negative selection in the thymus, the transcription factor AIRE, CD4+CD25+ regulatory T cells, and dendritic cells cooperate to produce and maintain tolerance. Cytokines modulate deriving immune processes and influence the local micro-environment. Multiple mechanisms are involved in tolerance breakdown: genetic factors (major histocompatibility complex haplotypes, polymorphisms in the cytotoxic T lymphocyte antigen gene and epigenetic alterations), environmental factors (mainly infections), impaired apoptosis, and the emergence of autoreactive naive lymphocytes. These events may be involved in the pathogenesis of endocrine diseases at several levels.

A central role for central tolerance

Recent elucidation of the role of central tolerance in preventing organ-specific autoimmunity has changed our concepts of self/nonself discrimination. This paradigmatic shift is largely attributable to the discovery of promiscuous expression of tissue-restricted self-antigens (TRAs) by medullary thymic epithelial cells (mTECs). TRA expression in mTECs mirrors virtually all tissues of the body, irrespective of developmental or spatio-temporal expression patterns. This review summarizes current knowledge on the cellular and molecular regulation of TRA expression in mTECs, outlines relevant mechanisms of antigen presentation and modes of tolerance induction, and discusses implications for the pathogenesis of autoimmune diseases and other biological processes such as fertility, pregnancy, puberty, and tumor defense.

Human T cell responses against melanoma

Many antigens recognized by autologous T lymphocytes have been identified on human melanoma. Melanoma patients usually mount a spontaneous T cell response against their tumor. But at some point, the responder T cells become ineffective, probably because of a local immunosuppressive process occurring at the tumor sites. Therapeutic vaccination of metastatic melanoma patients with these antigens is followed by tumor regressions only in a small minority of the patients. The T cell responses to the vaccines show correlation with the tumor regressions. The local immunosuppression may be the cause of the lack of vaccination effectiveness that is observed in most patients. In patients who do respond to the vaccine, the antivaccine T cells probably succeed in reversing focally this immunosuppression and trigger a broad activation of other antitumor T cells, which proceed to destroy the tumor.

Influence of CD4+CD25+ regulatory T cells on low/high-avidity CD4+ T cells following peptide vaccination

We have recently reported that NY-ESO-1-specific naive CD4+ T cell precursors exist in most individuals but are suppressed by CD4+CD25+ regulatory T cells (Tregs), while memory CD4+ T cell effectors against NY-ESO-1 are found only in cancer patients with spontaneous Ab responses to NY-ESO-1. In this study, we have analyzed mechanisms of CD4+ T cell induction following peptide vaccination in relation to susceptibility to Tregs. Specific HLA-DP4-restricted CD4+ T cell responses were elicited after vaccination with NY-ESO-1(157-170) peptide (emulsified in IFA) in patients with NY-ESO-1-expressing epithelial ovarian cancer. These vaccine-induced CD4+ T cells were detectable from effector/memory populations without requirement for in vitro CD4+CD25+ T cell depletion. However, they were only able to recognize NY-ESO-1(157-170) peptide but not naturally processed NY-ESO-1 protein and had much lower avidity compared with NY-ESO-1-specific pre-existing naive CD4+CD25- T cell precursors or spontaneously induced CD4+ T cell effectors of cancer patients with NY-ESO-1 Ab. We propose that vaccination with NY-ESO-1(157-170) peptide recruits low-avidity T cells with low sensitivity to Tregs and fails to modulate the suppressive effect of Tregs on high-avidity NY-ESO-1-specific T cell precursors.

TGF-beta signaling is required for the function of insulin-reactive T regulatory cells

We have previously isolated insulin-reactive Tregs from diabetic NOD mice designated 2H6, from which TCR transgenic mice were generated. The T cells from these 2H6 transgenic mice recognize insulin but have suppressive properties in vitro. They protect NOD mice in vivo from spontaneous development of diabetes and adoptive transfer of disease caused by polyclonal diabetogenic spleen cells as well as the highly diabetogenic monoclonal BDC2.5 TCR transgenic T cells that recognize an islet granule antigen. Using cells from both NOD and BDC2.5 mice that express a dominant-negative TGF-beta receptor type II (TGF-betaDNRII), we show that 2H6 T cells protected from disease by producing TGF-beta and that the ability of the target diabetogenic T cells to respond to TGF-beta was crucial. We further demonstrate that TGF-beta signaling in 2H6 cells was important for their protective properties, as 2H6 cells were unable to protect from adoptive transfer-induced diabetes if they were unable to respond to TGF-beta. Thus, our data demonstrate that insulin-specific regulatory cells protect from diabetes by virtue of their production of TGF-beta1 that acts in an autocrine manner to maintain their regulatory function and acts in a paracrine manner on the target cells.

Antigen-presenting cells expressing glutamate decarboxylase 67 were identified as epithelial cells in glutamate decarboxylase 67-GFP knock-in mouse thymus

Glutamate decarboxylase (GAD), which has two isoforms, GAD65, and GAD67, is responsible for synthesis of the major inhibitory neurotransmitter, gamma-aminobutyric acid. GAD is expressed predominantly in the central nervous system; recent reports suggest that GAD is also expressed in non-neuronal organs including the pancreas. In the pancreatic islets, GAD serves as one of the autoantigens in type I diabetes mellitus. Recent flow cytometric analyses have shown that a variety of self-antigens, including GAD, are ectopically transcribed and expressed in particular cell populations of the thymus, although consensus concerning the cellular phenotype has not been obtained. The aim of this study was to clarify the localization and cellular phenotype of GAD67-expressing cells in the thymus at a cellular level with a novel approach using GAD67-green fluorescent protein (GFP) knock-in mice, in which GFP is expressed specifically in GAD67-positive cells. GFP-positive cells were detected in the thymic medulla and were identified as epithelial cells by immunohistochemistry. Almost all GFP-positive cells were positive for major histocompatibility complex (MHC) class II antigen staining and were positive for both cytokeratin and Ulex Europaeus Agglutinin I, markers of medullary thymic epithelial cells, but were negative for CD11c, Gr-1, and CD45, markers of dendritic cells, macrophages, and B-lymphocytes, respectively.

Expression of aberrantly glycosylated tumor mucin-1 on human DC after transduction with a fiber-modified adenoviral vector

BACKGROUND

DC-presenting tumor Ag are currently being developed to be used as a vaccine in human cancer immunotherapy. To increase chances for successful therapy it is important to deliver full-length tumor Ag instead of loading single peptides.

METHODS

In this study we used a fiber-modified adenoviral vector (rAd5F35) containing full-length tumor Ag cDNA to transduce human monocyte (Mo)-derived DC in vitro. Cells were efficiently transduced and survived for at least 3 days after adenoviral transduction. Phenotype and function after maturation of Mo-DC were not impaired by infection with adenovirus particles. Expression of the tumor-associated Ag mucin-1 (MUC1) was detected using MAb defining different MUC1 glycoforms.

RESULTS

Non-transduced mature Mo-DC express endogenous MUC1 with normal glycosylation. After transduction with the rAd5F35-MUC1 adenoviral vector, Mo-DC also expressed MUC1 with tumor-associated glycosylation (Tn and T glycoforms), although no changes in mRNA levels of relevant glycosyltransferases could be demonstrated.

DISCUSSION

The presence of aberrantly glycosylated MUC1 may influence Ag presentation of the tumor glycoforms of MUC1 to immune cells, affecting tumor cell killing. These findings could be highly relevant to developing strategies for cancer immunotherapy based on DC vaccines using MUC1 as tumor Ag.

Persistence of autoreactive myelin oligodendrocyte glycoprotein (MOG)-specific T cell repertoires in MOG-expressing mice

Experimental autoimmune encephalomyelitis, an experimental murine model for multiple sclerosis, is induced by stimulation of myelin-specific T lymphocytes. Myelin oligodendrocyte glycoprotein (MOG), a minor component of myelin proteins, is a potent autoantigen which contributes extensively to the anti-myelin response. In the present work, immunoscope analyses and sequencing of the oligoclonal expansions revealed anti-MOG Valpha and Vbeta public repertoires in lymphocytes infiltrating the CNS of wild-type (WT) mice. Moreover, a subset of CNS-infiltrating CD4+ T lymphocytes bearing the public Vbeta8.2 segment have an inflammatory phenotype strongly suggesting that it is encephalitogenic. We then observed that, in lymph node cells of MOG-deficient and WT animals, the Valpha and Vbeta public repertoires expressed by MOG-specific T cells are identical in both strains of mice and correspond to those found in the CNS of WT animals. These findings indicate that the MOG immunodominant determinant is unable to induce tolerance by deletion, and public anti-MOG T cell repertoires are selected for, regardless of the presence of MOG in the thymus and peripheral organs.

Destructive cleavage of antigenic peptides either by the immunoproteasome or by the standard proteasome results in differential antigen presentation

The immunoproteasome (IP) is usually viewed as favoring the production of antigenic peptides presented by MHC class I molecules, mainly because of its higher cleavage activity after hydrophobic residues, referred to as the chymotrypsin-like activity. However, some peptides have been found to be better produced by the standard proteasome. The mechanism of this differential processing has not been described. By studying the processing of three tumor antigenic peptides of clinical interest, we demonstrate that their differential processing mainly results from differences in the efficiency of internal cleavages by the two proteasome types. Peptide gp100(209-217) (ITDQVPSFV) and peptide tyrosinase369-377 (YMDGTMSQV) are destroyed by the IP, which cleaves after an internal hydrophobic residue. Conversely, peptide MAGE-C2(336-344) (ALKDVEERV) is destroyed by the standard proteasome by internal cleavage after an acidic residue, in line with its higher postacidic activity. These results indicate that the IP may destroy some antigenic peptides due to its higher chymotrypsin-like activity, rather than favor their production. They also suggest that the sets of peptides produced by the two proteasome types differ more than expected. Considering that mature dendritic cells mainly contain IPs, our results have implications for the design of immunotherapy strategies.

Molecular characterisation of the t(1;15)(p22;q22) translocation in the prostate cancer cell line LNCaP

Although chromosome translocations are well-documented recurrent events in hematological malignancies and soft tissue sarcomas, their significance in carcinomas is less clear. We report here the molecular characterization of the reciprocal translocation t(1;15)(p22;q22) in the prostate carcinoma cell line, LNCaP. The chromosome 1 breakpoint was localized to a single BAC clone, RP11-290M5, by sequential FISH analysis of clones selected from the NCBI chromosome 1 map. This was further refined to a 580-bp region by Southern blot analysis. A 2.85-kb fragment spanning the der(1) breakpoint was amplified by long-range inverse PCR. The breakpoint on chromosome 1 was shown to lie between the CYR61 and the DDAH1 genes with the der(1) junctional sequence linking the CYR61 gene to the TSPAN3 (TM4SF8) gene on chromosome 15. Confirmatory PCR and FISH mapping of the der(15) showed loss of chromosome material proximal to the breakpoint on chromosome 15, containing the PSTPIP1 and RCN2 genes. On the available evidence we conclude that this translocation does not result in an in-frame gene fusion. Comparative expressed sequence hybridization (CESH) and comparative genomic hybridization (CGH) analysis, showed relative down-regulation of gene expression surrounding the breakpoint, but no gross change in genomic copy number. Real-time quantitative RT-PCR for genes around the breakpoint supported the CESH data. Therefore, here we may have revealed a gene down-regulation mechanism associated with a chromosome translocation, either through small deletion at the breakpoint or through another means of chromosome domain related gene regulation.

The why and how of thymocyte negative selection

The generation of T cell receptor (TCR) sequence diversity is the strength of adaptive immunity, yet is also the Achilles' heel. To purge highly self-reactive T cells from the immune system, generation of diversity has coevolved with a mechanism of negative selection. Recent studies have revealed new insights addressing the why and how of negative selection by examining situations in which negative selection has failed in human and animals models of autoimmunity. Both thymocyte extrinsic and intrinsic mechanisms are required to restrict the TCR repertoire to a non-autoreactive set. Negative selection also ensures that T cells emerge with receptors that are focussed on the peptide moiety of MHC-peptide complexes.

AIRE recruits multiple transcriptional components to specific genomic regions through tethering to nuclear matrix

Thymic selection requires that diverse self antigens be presented to developing thymocytes by stromal cells. Consistent with this function, medullary thymic epithelial cells have been shown to express a large number of genes, many of which are tissue restricted. Autoimmune regulator (AIRE) is a nuclear protein, which has recently been identified as a regulator of this process, however, the mechanism by which AIRE functions is not well understood. Here we use a transrepression assay to demonstrate that AIRE interacts with multiple components of the transcription complex including a novel interaction with the UBA domain protein, GBDR1. When AIRE is expressed in cultured human thymic epithelial cells, it tightly associates with nuclear matrix, suggesting that AIRE responsive genes may be localized to specific regions. Using a mathematical approach we have re-analyzed an Affymetrix dataset identifying AIRE responsive genes and show that they tend to localize to specific regions of the genome. Together, these data suggest that AIRE regulates gene expression by recruiting components of the transcription complex to specific regions of the genome via interactions with nuclear matrix.

CD4+CD25+ Regulatory T Cells Inhibit the Antigen-Dependent Expansion of Self-Reactive T Cells In Vivo

A deficiency of CD4+CD25+ regulatory T cells (CD25+ Tregs) in lymphopenic mice can result in the onset of autoimmune gastritis. The gastric H/K ATPase alpha (H/Kalpha) and beta (H/Kbeta) subunits are the immunodominant autoantigens recognized by effector CD4+ T cells in autoimmune gastritis. The mechanism by which CD25+ Tregs suppress autoimmune gastritis in lymphopenic mice is poorly understood. To investigate the antigenic requirements for the genesis and survival of gastritis-protecting CD25+ Tregs, we analyzed mice deficient in H/Kbeta and H/Kalpha, as well as a transgenic mouse line (H/Kbeta-tsA58 Tg line 224) that lacks differentiated gastric epithelial cells. By adoptive transfer of purified T cell populations to athymic mice, we show that the CD25+ Treg population from mice deficient in either one or both of H/Kalpha and H/Kbeta, or from the H/Kbeta-tsA58 Tg line 224 mice, is equally effective in suppressing the ability of polyclonal populations of effector CD4+ T cells to induce autoimmune gastritis. Furthermore, CD25+ Tregs, from either wild-type or H/Kalpha-deficient mice, dramatically reduced the expansion of pathogenic H/Kalpha-specific TCR transgenic T cells and the induction of autoimmune gastritis in athymic recipient mice. Proliferation of H/Kalpha-specific T cells in lymphopenic hosts occurs predominantly in the paragastric lymph node and was dependent on the presence of the cognate H/Kalpha Ag. Collectively, these studies demonstrate that the gastritis-protecting CD25+ Tregs do not depend on the major gastric Ags for their thymic development or their survival in the periphery, and that CD25+ Tregs inhibit the Ag-specific expansion of pathogenic T cells in vivo.

Culture of melanoma cells in 3-dimensional architectures results in impaired immunorecognition by cytotoxic T lymphocytes specific for Melan-A/MART-1 tumor-associated antigen

OBJECTIVE

To assess the effects of the culture of melanoma cells in 3-dimensional (3D) architectures on their immunorecognition by cytotoxic T lymphocytes (CTLs) specific for tumor-associated antigens.

SUMMARY BACKGROUND DATA

Growth in 3D architectures has been shown to promote the resistance of cancers to treatment with drugs, cytokines, or irradiation, thereby potentially playing an important role in tumor expansion. We investigated the effects of 3D culture on the recognition of melanoma cells by antigen-specific HLA class I-restricted CTLs.

METHODS

Culture of HBL melanoma cells expressing Melan-A/Mart-1 tumor-associated antigen and HLA-A0201 on poly-2-hydroxyethyl methacrylate (polyHEMA)-coated plates resulted in the generation of aggregates of 400- to 500-microm diameters containing on average 30,000 cells and characterized by slower proliferation, as compared with monolayer (2-dimensional) cultures. HLA-A0201 restricted Melan-A/Mart-127-35-specific CTL clones were used to evaluate tumor cell immunorecognition measured as specific IFN-gamma production. Comparative gene and protein expression in 2D and 3D cultures was studied by real-time PCR and flow cytometry, respectively. Overall differences in gene expression profiles between 2D and 3D cultures were evaluated by high-density oligonucleotide array hybridization.

RESULTS

HLA-A0201 restricted Melan-A/Mart-127-35 specific CTL clones produced high amounts of IFN-gamma upon short-term (4-24 hours) coincubation with HBL cells cultured in 2D but not in 3D, thus suggesting altered antigen recognition. Indeed, Melan-A/Mart-1 expression, at both gene and protein levels, was significantly decreased in 3D as compared with 2D cultures. Concomitantly, a parallel decrease of HLA class I molecule expression was also observed. Differential gene profiling studies on HBL cells showed an increased expression of genes encoding molecules involved in intercellular adhesion, such as junctional adhesion molecule 2 and cadherin-like 1 (>20- and 8-fold up-regulated, respectively) in 3D as compared with 2D cultures.

CONCLUSIONS

Taken together, our data suggest that mere growth of melanoma cells in 3D architectures, in the absence of immunoselective pressure, may result in defective recognition by tumor-associated antigen-specific CTL.

PROTECTING THE PUMP: Controlling Myocardial Inflammatory Responses

Because of the anatomy, function, and nonregenerative nature of the myocardium, inflammation in this tissue is not well tolerated. Nevertheless, various diseases of the heart are characterized by inflammatory responses involving the effector mechanisms of innate and adaptive (lymphocyte-dependent) immunity. The innate immune response to ischemia-reperfusion injury is, by far, the most common cause of myocardial inflammation. Innate responses may have beneficial influences that preserve myocardial function in the short term but may be maladaptive in chronic states. Adaptive responses in the myocardium occur with infection or loss of tolerance, and lead to myocarditis. Given the narrow margin for benefit of cardiac inflammation, special regulatory mechanisms likely raise the threshold, compared to other tissues, for the induction and persistence of adaptive immune responses. These mechanisms include strong central and peripheral T cell tolerance to heart antigens and induction of anti-inflammatory feedback mechanisms involving cytokines such as interferon-gamma.

A MAGE-1 antigenic peptide recognized by human cytolytic T lymphocytes on HLA-A2 tumor cells

"Cancer-germline" genes such as those of the MAGE family are expressed in many tumors and in male germline cells, but are silent in normal tissues. They encode shared tumor-specific antigens that have been used in therapeutic vaccination trials of cancer patients. It was previously demonstrated that MAGE-1 peptide KVLEYVIKV was presented by HLA-A 0201 molecules on the surface of a human breast carcinoma cell line, but no human specific CTL had been isolated so far. Here, we have used HLA-A2/MAGE-1 fluorescent multimers to isolate from blood cells three human CTL clones that recognized the MAGE-1 peptide. These clones killed efficiently HLA-A2 tumor cells expressing MAGE-1, whether or not they were treated with IFN-gamma, suggesting that the MAGE-1 antigen is processed efficiently by both the standard proteasome and the immunoproteasome. These results indicate that the MAGE-1.A2 peptide can be used for antitumoral vaccination.

Shaping the T cell repertoire to a bona fide autoantigen: lessons from autoimmune gastritis

Murine autoimmune gastritis is one of the most well-defined organ-specific autoimmune diseases. CD4(+) T cells, which mediate the disease, recognize the highly abundant gastric H(+)/K(+) ATPase heterodimer. The H(+)/K(+) ATPase alpha subunit is also expressed in the thymus, in an aire-independent manner, whereas the H(+)/K(+) ATPase beta subunit is absent from the thymus. Analysis of both H(+)/K(+) ATPase-specific T cell receptor transgenic mice with different affinities for the gastric antigen and mice deficient in the H(+)/K(+) ATPase subunits has provided information on thymic and peripheral selection events. The H(+)/K(+) ATPase antigens play an important role in purging the repertoire of gastritogenic T cells, and recent data have suggested that this tolerance induction occurs primarily in the periphery. The gastritis system provides a powerful approach to determine the impact of peripheral antigen presentation in the target organ draining lymph node on tolerance and autoimmune disease.

Central tolerance: learning self-control in the thymus

In the past few years, there has been a flurry of discoveries and advancements in our understanding of how the thymus prepares T cells to exist at peace in normal healthy tissue: that is, to be self-tolerant. In the thymus, one of the main mechanisms of T-cell central tolerance is clonal deletion, although the selection of regulatory T cells is also important and is gaining enormous interest. In this Review, we discuss the emerging consensus about which models of clonal deletion are most physiological, and we review recent data that define the molecular mechanisms of central tolerance.

Molecular defects in T- and B-cell primary immunodeficiency diseases

More than 120 inherited primary immunodeficiency diseases have been discovered in the past five decades, and the precise genetic defect in many of these diseases has now been identified. Increasing understanding of these molecular defects has considerably influenced both basic and translational research, and this has extended to many branches of medicine. Recent advances in both diagnosis and therapeutic modalities have allowed these defects to be identified earlier and to be more precisely defined, and they have also resulted in more promising long-term outcomes. The prospect of gene therapy continues to be included in the armamentarium of treatment considerations, because these conditions could be among the first to benefit from gene-therapy trials in humans.