O timo é um orgão linfóide primário, no qual ocorre a indução da tolerância imunológica central aos antígenos do próprio que são expressos pelos tecidos periféricos (PTAs). A medula tímica é formada por células tímicas medulares epiteliais (mTECs) que expressam centenas desses PTAs que representam virtualmente todos os órgãos e tecidos do corpo. Esse fenômeno foi denominado de expressão gênica promíscua (PGE) a qual é parcialmente regulada pelo modulador da transcrição Autoimmune regulator (Aire). Os precursores de células T oriundos da medula óssea migram para o timo (agora são denominados de timócitos) e na medula desse órgão, passam pela seleção negativa mediada pelas mTECs. As células sobreviventes evoluem para células T maduras e funcionais que migram para a periferia com capacidade de reconhecimento das moléculas de MHC e tolerantes aos PTAs. Além de controlar a transcrição de genes PTAs, Aire também controla a expressão de microRNAs (miRNAs), relacionados com a integridade e funcionalidade do microambiente tímico. A seleção negativa no timo é um processo essencial para a manutenção da autotolerância imunológica e o desbalanço desse processo está associado com o desenvolvimento de doenças autoimunes como, por exemplo, o diabetes mellitus do tipo 1 (DM1).Tendo em vista essas premissas, nosso trabalho se fundamentou em duas hipóteses: 1) Variações na expressão do gene Aire podem perturbar a expressão de genes PTAs e miRNAs no timo, causando alterações na PGE, 2) A expressão balanceada de genes como Aire e/ou PTAs nas mTECs, é fundamental para a integridade da tolerância central. O desbalanço na expressão desses genes, está associado com a emergência do diabetes mellitus tipo 1 no camundongo. Para testar nossa primeira hipótese efetuamos o silenciamento de Aire (Aire knockdown) por meio de eletrotransfeção de RNA interferente (siRNA) anti-Aire in vivo no timo de camundongos BALB/c. Análises do transcriptoma (mRNAs) e miRNoma (miRNAs) das mTECs, revelaram que silenciamento parcial e transitório de Aire foi suficiente para afetar a expressão de PTAs Aire dependentes bem como a de miRNAs. Redes de interação miRNA-mRNA, revelaram que o controle pós-transcricional da PGE também é afetado pelo silenciamento de Aire. Os resultados encontrados revelam que Aire e miRNAs podem formar uma via essencial durante a indução da tolerância central. Para testar nossa segunda hipótese comparamos o transcriptoma de mTECs de camundongos BALB/c (linhagem não-autoimune) com mTECs de camundongos non-obese diabetic NOD (modelo animal utilizado nos estudos de DM1 autoimune). Nossos resultados revelaram que a expressão transcricional de autoantígenos relacionados ao DM1 está desbalanceada em camundongos NOD já numa fase precoce, quando esses animais ainda não apresentavam a doença clínica (fase pré-diabética). Inesperadamente, os níveis transcrionais de Aire apresentaram-se equivalentes no timo dessas duas linhagens, porém os níveis da proteína AIRE estavam reduzidos no timo da linhagem NOD. Esses resultados sugerem a participação de algum mecanismo de atenuação póstrascricional de Aire nessa linhagem provavelmente envolvendo atuação de miRNAs. Isso poderia explicar o desbalanço de PTAs Aire-dependentes e a repressão autoantígenos relacionados ao DM1. Concluímos que nossos resultados, além de abrir novas perspectivas para pesquisas nesta área, contribuem com melhor compreensão dos mecanismos moleculares desencadeados por Aire e por miRNAs no controle da expressão de autoantígenos no timo o que é importante para a tolerância imunológica central. / The thymus is a primary lymphoid organ, in which occurs in the induction of central immune tolerance to self peripheral tissue antigens (PTAs). The thymic medulla is formed by medullary thymic epithelial cells (mTECs) expressing hundreds of such PTAs representing virtually all organs and tissues of the body. This phenomenon has been termed promiscuous gene expression (PGE), which is partially regulated by the Autoimmune regulator (Aire) gene. The T cell precursors derived from the bone marrow migrate to the thymus (now termed thymocytes). A part of these thymocytes are eliminated by negative selection mediated mTEC cells. The surviving cells to evolve and functional mature T cells that migrate to the periphery and are capable of recognizing MHC molecules and are tolerant to PTAs. In addition to controlling the transcription of PTA genes, Aire also controls the expression of microRNAs (miRNAs). The negative selection in the thymus is a process essential to the maintenance of immunologic self-tolerance and imbalance of this process is associated with the development of autoimmune diseases such as type 1 diabetes mellitus (DM1) . Given these assumptions, our work was based on two hypothesis: 1) Changes in the expression of the Aire gene can disrupt the expression of PTA genes and miRNAs in the thymus, causing changes in PGE, 2) The balanced expression of Aire / or PTA genes in mTECs is fundamental for central tolerance. The imbalance in the expression of these genes is associated with the emergence of type 1 diabetes in mice. To test our first hypothesis we made Aire silencing (Aire knockdown) through electrotransfection of anti - Aire interfering RNA (siRNA) in vivo in the thymus of BALB/c mice. Analysis of the transcriptome (mRNAs) and miRNome (miRNAs) of mTECs revealed that partial and transient silencing of Aire was enough to affect the expression of Aire - dependent PTAs as well as miRNAs. miRNA -mRNA interaction networks revealed that the posttranscriptional control of PGE is also affected by the silencing of Aire. The results show that Aire and can form an miRNA pathway essential for the induction of central tolerance. To test our second hypothesis we compared the transcriptome of mTECs of BALB/c mice (non-autoimmune strain) with mTECs from non - obese diabetic NOD (animal model used in studies of autoimmune DM1) . Our results indicate that the transcriptional expression of DM1-related autoantigens are unbalanced in NOD mice in an very early stage, when these animals have not had clinical disease (pre-diabetic period). Unexpectedly, the transcriptional levels of Aire in the thymus was equivalent in these two strains, but the AIRE protein levels were reduced in thymus of NOD strain. These results suggest that some mechanism of post-transcriptional attenuation of Aire is acting in this lineage probably involving action of miRNAs . This could explain the imbalance of Aire - dependent PTAs and repression autoantigens related to DM1. Our results open perspectives for research in this area, contributing to better understanding the molecular mechanisms triggered by Aire and miRNAs in control of the expression of autoantigens in the thymus, which is important for the central immune tolerance.

O timo é um orgão linfóide primário, no qual ocorre a indução da tolerância imunológica central aos antígenos do próprio que são expressos pelos tecidos periféricos (PTAs). A medula tímica é formada por células tímicas medulares epiteliais (mTECs) que expressam centenas desses PTAs que representam virtualmente todos os órgãos e tecidos do corpo. Esse fenômeno foi denominado de expressão gênica promíscua (PGE) a qual é parcialmente regulada pelo modulador da transcrição Autoimmune regulator (Aire). Os precursores de células T oriundos da medula óssea migram para o timo (agora são denominados de timócitos) e na medula desse órgão, passam pela seleção negativa mediada pelas mTECs. As células sobreviventes evoluem para células T maduras e funcionais que migram para a periferia com capacidade de reconhecimento das moléculas de MHC e tolerantes aos PTAs. Além de controlar a transcrição de genes PTAs, Aire também controla a expressão de microRNAs (miRNAs), relacionados com a integridade e funcionalidade do microambiente tímico. A seleção negativa no timo é um processo essencial para a manutenção da autotolerância imunológica e o desbalanço desse processo está associado com o desenvolvimento de doenças autoimunes como, por exemplo, o diabetes mellitus do tipo 1 (DM1).Tendo em vista essas premissas, nosso trabalho se fundamentou em duas hipóteses: 1) Variações na expressão do gene Aire podem perturbar a expressão de genes PTAs e miRNAs no timo, causando alterações na PGE, 2) A expressão balanceada de genes como Aire e/ou PTAs nas mTECs, é fundamental para a integridade da tolerância central. O desbalanço na expressão desses genes, está associado com a emergência do diabetes mellitus tipo 1 no camundongo. Para testar nossa primeira hipótese efetuamos o silenciamento de Aire (Aire knockdown) por meio de eletrotransfeção de RNA interferente (siRNA) anti-Aire in vivo no timo de camundongos BALB/c. Análises do transcriptoma (mRNAs) e miRNoma (miRNAs) das mTECs, revelaram que silenciamento parcial e transitório de Aire foi suficiente para afetar a expressão de PTAs Aire dependentes bem como a de miRNAs. Redes de interação miRNA-mRNA, revelaram que o controle pós-transcricional da PGE também é afetado pelo silenciamento de Aire. Os resultados encontrados revelam que Aire e miRNAs podem formar uma via essencial durante a indução da tolerância central. Para testar nossa segunda hipótese comparamos o transcriptoma de mTECs de camundongos BALB/c (linhagem não-autoimune) com mTECs de camundongos non-obese diabetic NOD (modelo animal utilizado nos estudos de DM1 autoimune). Nossos resultados revelaram que a expressão transcricional de autoantígenos relacionados ao DM1 está desbalanceada em camundongos NOD já numa fase precoce, quando esses animais ainda não apresentavam a doença clínica (fase pré-diabética). Inesperadamente, os níveis transcrionais de Aire apresentaram-se equivalentes no timo dessas duas linhagens, porém os níveis da proteína AIRE estavam reduzidos no timo da linhagem NOD. Esses resultados sugerem a participação de algum mecanismo de atenuação póstrascricional de Aire nessa linhagem provavelmente envolvendo atuação de miRNAs. Isso poderia explicar o desbalanço de PTAs Aire-dependentes e a repressão autoantígenos relacionados ao DM1. Concluímos que nossos resultados, além de abrir novas perspectivas para pesquisas nesta área, contribuem com melhor compreensão dos mecanismos moleculares desencadeados por Aire e por miRNAs no controle da expressão de autoantígenos no timo o que é importante para a tolerância imunológica central. / The thymus is a primary lymphoid organ, in which occurs in the induction of central immune tolerance to self peripheral tissue antigens (PTAs). The thymic medulla is formed by medullary thymic epithelial cells (mTECs) expressing hundreds of such PTAs representing virtually all organs and tissues of the body. This phenomenon has been termed promiscuous gene expression (PGE), which is partially regulated by the Autoimmune regulator (Aire) gene. The T cell precursors derived from the bone marrow migrate to the thymus (now termed thymocytes). A part of these thymocytes are eliminated by negative selection mediated mTEC cells. The surviving cells to evolve and functional mature T cells that migrate to the periphery and are capable of recognizing MHC molecules and are tolerant to PTAs. In addition to controlling the transcription of PTA genes, Aire also controls the expression of microRNAs (miRNAs). The negative selection in the thymus is a process essential to the maintenance of immunologic self-tolerance and imbalance of this process is associated with the development of autoimmune diseases such as type 1 diabetes mellitus (DM1) . Given these assumptions, our work was based on two hypothesis: 1) Changes in the expression of the Aire gene can disrupt the expression of PTA genes and miRNAs in the thymus, causing changes in PGE, 2) The balanced expression of Aire / or PTA genes in mTECs is fundamental for central tolerance. The imbalance in the expression of these genes is associated with the emergence of type 1 diabetes in mice. To test our first hypothesis we made Aire silencing (Aire knockdown) through electrotransfection of anti - Aire interfering RNA (siRNA) in vivo in the thymus of BALB/c mice. Analysis of the transcriptome (mRNAs) and miRNome (miRNAs) of mTECs revealed that partial and transient silencing of Aire was enough to affect the expression of Aire - dependent PTAs as well as miRNAs. miRNA -mRNA interaction networks revealed that the posttranscriptional control of PGE is also affected by the silencing of Aire. The results show that Aire and can form an miRNA pathway essential for the induction of central tolerance. To test our second hypothesis we compared the transcriptome of mTECs of BALB/c mice (non-autoimmune strain) with mTECs from non - obese diabetic NOD (animal model used in studies of autoimmune DM1) . Our results indicate that the transcriptional expression of DM1-related autoantigens are unbalanced in NOD mice in an very early stage, when these animals have not had clinical disease (pre-diabetic period). Unexpectedly, the transcriptional levels of Aire in the thymus was equivalent in these two strains, but the AIRE protein levels were reduced in thymus of NOD strain. These results suggest that some mechanism of post-transcriptional attenuation of Aire is acting in this lineage probably involving action of miRNAs . This could explain the imbalance of Aire - dependent PTAs and repression autoantigens related to DM1. Our results open perspectives for research in this area, contributing to better understanding the molecular mechanisms triggered by Aire and miRNAs in control of the expression of autoantigens in the thymus, which is important for the central immune tolerance.

O timo é um órgão linfoide primário essencial para a manutenção da tolerância central através da seleção e eliminação de células T autoreativas. Precursores de células T, oriundas da medula óssea, chegam ao timo e migram do córtex para região da medula. As células epiteliais medulares tímicas (mTECs) expressam em sua superfície antígenos de tecidos periféricos (em inglês tissue-restricted antigens ou TRAs) que representam autoantígenos de todos os tecidos do corpo. Atuando como um fator de transcrição não clássico em células mTEC, o gene Autoimmune Regulator (Aire) desempenha um papel na expressão dos TRAs, cuja proteína codificada libera a RNA polimerase II (RNA Pol II) ancorada na cromatina e regula a expressão de mRNAs na glândula timo. A função biológica deste gene está ligada à indução de tolerância imunológica central impedindo o aparecimento de doenças autoimunes. Isso é resultado da seleção negativa de timócitos (precursores de células T) autoreativos que interagem fisicamente com as mTECs. Os timócitos autoreativos que reconhecem os TRAs como elementos estranhos são eliminados por apoptose. O co-cultivo de mTECs com timócitos representa um sistema-modelo in vitro adequado para se aproximar da interação celular que ocorre dentro do timo. Os resultados anteriores do nosso laboratório demonstraram que além do controle de mRNA de TRAs, o gene Aire também participa da modulação de miRNAs em mTECs uma vez que estas espécies de RNA são transcritas pela RNA Pol II. Continuando com essa linha de estudos, neste trabalho nós demonstramos pela primeira vez que Aire também modula a expressão de long noncoding RNAs (lncRNAs) em mTECs. Para isto fizemos uso da estratégia da perda de função analisando a expressão dessa espécie de RNA, assim como de mRNAs, em células mTEC Aire +/+ e mTEC Aire nocautes (KO Aire -/-) obtidas pela edição gênica por Crispr-Cas9. O transcriptoma dessas células que passaram ou não por adesão com timócitos, foi então analisado por hibridizações com microarrays. Isso evidenciou que Aire e adesão celular influenciam a expressão tanto de mRNAs como de lncRNAs. A reconstrução de redes de interação lncRNAs-mRNAs possibilitou evidenciar uma nova via de regulação pós-transcricional em células mTEC. / The thymus is a primary lymphoid organ essential for the maintenance of central tolerance through the selection and elimination of autoreactive T cells. Precursors of T cells, originating from the bone marrow, reach the thymus and migrate from the thymic cortex to the medullary region. Thymic medullary epithelial cells (mTECs) express on their surface tissue-restricted antigens (TRAs) that represent autoantigens of all tissues in the body. Acting as a non-classical transcription factor in mTEC cells, the Autoimmune regulator (Aire) gene plays a role in the expression of TRAs, whose encoded protein releases the RNA polymerase II (RNA Pol II) anchored in the chromatin and regulates the expression of mRNAs in the thymus gland. The biological function of this gene is associated to the induction of central immune tolerance preventing the onset of autoimmune diseases. This is a result of negative selection of autoreactive thymocytes (T cell precursors) that interact physically with mTECs. Self-reactive thymocytes that recognize TRAs as foreign elements are eliminated by apoptosis. The co-culture of mTECs with thymocytes represents an appropriate in vitro model system to approximate the cellular interaction that occurs within the thymus. Previous results from our laboratory demonstrated that in addition to the control of TRA mRNAs, Aire also participates in the modulation of miRNAs in mTECs since these RNA species are transcribed by RNA Pol II. Continuing with this line of studies, in this study we demonstrate for the first time that Aire also modulates the expression of long non-coding RNAs (lncRNAs) in mTECs. For this, we used the loss-of-function strategy to analyze the expression of this RNA species, as well as mRNAs in mTEC Aire + / + or Aire knockout mTEC cells (KO Aire - / -) obtained by the gene editing by Crispr-Cas9. The transcriptome of these cells, whether or not adhered to thymocytes, was then analyzed by microarray hybridizations. This demonstrated that Aire and cell adhesion influence the expression of both mRNAs and lncRNAs. The reconstruction of lncRNAs-mRNAs interaction networks made possible to evidence a new post-transcriptional regulation pathway in mTEC cells.

O crosstalk entre timócitos e células epiteliais tímicas é crucial para o desenvolvimento das células T e estabelecimento da tolerância central. Células tímicas epiteliais medulares (mTECs) contribuem para a autotolerância por meio da expressão ectópica de antígenos restritos aos tecidos (TRAs). A expressão de TRAs em mTECs é altamente dependente do gene Autoimmune Regulator (Aire). Por meio do reconhecimento de TRAs com alta afinidade, células T autoreativas são selecionadas negativamente do pool de timócitos em desenvolvimento. Apesar do papel de Aire na indução da tolerância central ser bem conhecido, os mecanismos celulares e moleculares precisos do processo permanecem obscuros. Nesse estudo, hipotetizamos que perturbações na expressão do gene Aire influenciam a adesão entre mTECs e timócitos, o que poderia resultar em um desequilíbrio na imunotolerância a antígenos próprios. Um ensaio funcional realizado com timócitos frescos, extraídos de um timo normal de camundongo e cocultivados com células epiteliais tímicas medulares da linhagem mTEC 3.10, demonstrou que a inibição do gene Aire por meio de RNA de interferência reduziu significativamente a capacidade das mTECs de promover a adesão dos timócitos. Análises por microarray revelaram que o silenciamento do gene Aire nas células mTEC 3.10 causou a modulação de mais de 1000 genes, alguns que codificam TRAs, outros que codificam proteínas envolvidas na adesão celular, como VCAM-1, e também outros que codificam moléculas coestimuladoras como CD80. Esses resultados contribuem para uma melhor compreensão do papel de Aire no controle da adesão mTEC-timócitos, a qual constitui um processo essencial para a seleção negativa de timócitos autoreativos / The crosstalk between thymocytes and thymic epithelial cells is critical for T cell development and the establishment of central tolerance. Medullary thymic epithelial cells (mTECs) contribute to self-tolerance through the ectopic expression of tissuerestricted antigens (TRAs) in the thymus. TRAs expression in mTECs is largely dependent on Autoimmune Regulator (Aire) gene. Through the recognition of TRAs with high affinity, developing autoreactive T cells are negatively select from the pool of developing thymocytes. Although the role of Aire in the induction of central tolerance is well known, the precise cellular and molecular mechanisms remain unclear. In this study, we hypothesize that disturbance in Aire gene expression influences adhesion between mTECs and thymocytes, which could result in an imbalance in immune-tolerance to self-antigens. A functional assay performed with fresh thymocytes dissociated from a normal mouse thymus and co-cultured with a medullary thymic epithelial cell line named mTEC 3.10, demonstrated that Aire RNAi knockdown significantly decreased the ability of mTECs to promote thymocyte adhesion. Microarray analysis revealed that Aire knockdown of the murine mTEC 3.10 cell line led to the modulation of more than 1000 genes, some of them coding for TRAs, others for proteins involved in cell adhesion like VCAM-1 and also for costimulatory molecules like CD80. These results contribute to a better understanding of the role of Aire in the control of mTEC-thymocyte adhesion, which is an essential process for negative selection of autoreactive thymocytes

O crosstalk entre timócitos e células epiteliais tímicas é crucial para o desenvolvimento das células T e estabelecimento da tolerância central. Células tímicas epiteliais medulares (mTECs) contribuem para a autotolerância por meio da expressão ectópica de antígenos restritos aos tecidos (TRAs). A expressão de TRAs em mTECs é altamente dependente do gene Autoimmune Regulator (Aire). Por meio do reconhecimento de TRAs com alta afinidade, células T autoreativas são selecionadas negativamente do pool de timócitos em desenvolvimento. Apesar do papel de Aire na indução da tolerância central ser bem conhecido, os mecanismos celulares e moleculares precisos do processo permanecem obscuros. Nesse estudo, hipotetizamos que perturbações na expressão do gene Aire influenciam a adesão entre mTECs e timócitos, o que poderia resultar em um desequilíbrio na imunotolerância a antígenos próprios. Um ensaio funcional realizado com timócitos frescos, extraídos de um timo normal de camundongo e cocultivados com células epiteliais tímicas medulares da linhagem mTEC 3.10, demonstrou que a inibição do gene Aire por meio de RNA de interferência reduziu significativamente a capacidade das mTECs de promover a adesão dos timócitos. Análises por microarray revelaram que o silenciamento do gene Aire nas células mTEC 3.10 causou a modulação de mais de 1000 genes, alguns que codificam TRAs, outros que codificam proteínas envolvidas na adesão celular, como VCAM-1, e também outros que codificam moléculas coestimuladoras como CD80. Esses resultados contribuem para uma melhor compreensão do papel de Aire no controle da adesão mTEC-timócitos, a qual constitui um processo essencial para a seleção negativa de timócitos autoreativos / The crosstalk between thymocytes and thymic epithelial cells is critical for T cell development and the establishment of central tolerance. Medullary thymic epithelial cells (mTECs) contribute to self-tolerance through the ectopic expression of tissuerestricted antigens (TRAs) in the thymus. TRAs expression in mTECs is largely dependent on Autoimmune Regulator (Aire) gene. Through the recognition of TRAs with high affinity, developing autoreactive T cells are negatively select from the pool of developing thymocytes. Although the role of Aire in the induction of central tolerance is well known, the precise cellular and molecular mechanisms remain unclear. In this study, we hypothesize that disturbance in Aire gene expression influences adhesion between mTECs and thymocytes, which could result in an imbalance in immune-tolerance to self-antigens. A functional assay performed with fresh thymocytes dissociated from a normal mouse thymus and co-cultured with a medullary thymic epithelial cell line named mTEC 3.10, demonstrated that Aire RNAi knockdown significantly decreased the ability of mTECs to promote thymocyte adhesion. Microarray analysis revealed that Aire knockdown of the murine mTEC 3.10 cell line led to the modulation of more than 1000 genes, some of them coding for TRAs, others for proteins involved in cell adhesion like VCAM-1 and also for costimulatory molecules like CD80. These results contribute to a better understanding of the role of Aire in the control of mTEC-thymocyte adhesion, which is an essential process for negative selection of autoreactive thymocytes

<p>Autoimmune diseases develop when the immune system fails to distinguish self from non-self or when the immune system is hypersensitive to endogenous or exogenous danger signals, or when a tissue erroneously sends a danger signal to the immune system. The education of the immune system to distinguish self from non-self is mainly carried out in the thymus and gives rise to central tolerance, whereas the ability to sense a danger or a healthy tissue constitutes peripheral tolerance. In these studies we have investigated the peripheral tolerance mechanisms controlled by the autoimmune regulator <i>(Aire)</i> gene in Aire deficient mice, an animal model of the monogenic disease autoimmune polyendocrine syndrome type I (APS I).</p><p>Aire-/- mice displayed increased numbers of myeloid-derived antigen-presenting cells (APCs) in the spleen, lymph nodes and peritoneum as well as more blood monocytes and metallophilic macrophages in the spleen. Monocytes were also increased in the blood of APS I patients. Monocyte precursors displayed an accelerated development in the bone marrow of Aire-/- mice, and Aire-/- APCs had an altered phenotype that caused an increased immune response in several different contexts. Aire-/- splenic and lymph node dendritic cells had an increased ability to activate naive T cells, partly as a result of an upregulated expression of the costimulatory molecule VCAM-1. In Aire-/- mice increased activity of the metallophilic macrophages in the splenic marginal zone seems to be responsible both for the activated phenotype of marginal zone B cells and for the frequent development of marginal zone lymphoma with aging. In a TCR transgenic model Aire deficiency caused an increased superantigen-mediated TCR revision in the spleen, perhaps as a result of the altered phenotype of APCs in the spleen. Finally, Aire was shown to influence autoimmune disease development by a macrophage-dependent mechanism in diabetes induced with multiple low dose streptozotocin injections.</p><p>These results indicate that Aire has an important function in peripheral tolerance by controlling the phenotype of myeloid-derived APCs and thereby regulating the activation of T and B lymphocytes.</p> / <p>Autoimmune diseases develop when the immune system fails to distinguish self from non-self or when the immune system is hypersensitive to endogenous or exogenous danger signals, or when a tissue erroneously sends a danger signal to the immune system. The education of the immune system to distinguish self from non-self is mainly carried out in the thymus and gives rise to central tolerance, whereas the ability to sense a danger or a healthy tissue constitutes peripheral tolerance. In these studies we have investigated the peripheral tolerance mechanisms controlled by the autoimmune regulator <i>(Aire)</i> gene in Aire deficient mice, an animal model of the monogenic disease autoimmune polyendocrine syndrome type I (APS I).</p><p>Aire-/- mice displayed increased numbers of myeloid-derived antigen-presenting cells (APCs) in the spleen, lymph nodes and peritoneum as well as more blood monocytes and metallophilic macrophages in the spleen. Monocytes were also increased in the blood of APS I patients. Monocyte precursors displayed an accelerated development in the bone marrow of Aire-/- mice, and Aire-/- APCs had an altered phenotype that caused an increased immune response in several different contexts. Aire-/- splenic and lymph node dendritic cells had an increased ability to activate naive T cells, partly as a result of an upregulated expression of the costimulatory molecule VCAM-1. In Aire-/- mice increased activity of the metallophilic macrophages in the splenic marginal zone seems to be responsible both for the activated phenotype of marginal zone B cells and for the frequent development of marginal zone lymphoma with aging. In a TCR transgenic model Aire deficiency caused an increased superantigen-mediated TCR revision in the spleen, perhaps as a result of the altered phenotype of APCs in the spleen. Finally, Aire was shown to influence autoimmune disease development by a macrophage-dependent mechanism in diabetes induced with multiple low dose streptozotocin injections.</p><p>These results indicate that Aire has an important function in peripheral tolerance by controlling the phenotype of myeloid-derived APCs and thereby regulating the activation of T and B lymphocytes.</p>

Autoimmune diseases develop when the immune system fails to distinguish self from non-self or when the immune system is hypersensitive to endogenous or exogenous danger signals, or when a tissue erroneously sends a danger signal to the immune system. The education of the immune system to distinguish self from non-self is mainly carried out in the thymus and gives rise to central tolerance, whereas the ability to sense a danger or a healthy tissue constitutes peripheral tolerance. In these studies we have investigated the peripheral tolerance mechanisms controlled by the autoimmune regulator (Aire) gene in Aire deficient mice, an animal model of the monogenic disease autoimmune polyendocrine syndrome type I (APS I). Aire-/- mice displayed increased numbers of myeloid-derived antigen-presenting cells (APCs) in the spleen, lymph nodes and peritoneum as well as more blood monocytes and metallophilic macrophages in the spleen. Monocytes were also increased in the blood of APS I patients. Monocyte precursors displayed an accelerated development in the bone marrow of Aire-/- mice, and Aire-/- APCs had an altered phenotype that caused an increased immune response in several different contexts. Aire-/- splenic and lymph node dendritic cells had an increased ability to activate naive T cells, partly as a result of an upregulated expression of the costimulatory molecule VCAM-1. In Aire-/- mice increased activity of the metallophilic macrophages in the splenic marginal zone seems to be responsible both for the activated phenotype of marginal zone B cells and for the frequent development of marginal zone lymphoma with aging. In a TCR transgenic model Aire deficiency caused an increased superantigen-mediated TCR revision in the spleen, perhaps as a result of the altered phenotype of APCs in the spleen. Finally, Aire was shown to influence autoimmune disease development by a macrophage-dependent mechanism in diabetes induced with multiple low dose streptozotocin injections. These results indicate that Aire has an important function in peripheral tolerance by controlling the phenotype of myeloid-derived APCs and thereby regulating the activation of T and B lymphocytes. / Autoimmune diseases develop when the immune system fails to distinguish self from non-self or when the immune system is hypersensitive to endogenous or exogenous danger signals, or when a tissue erroneously sends a danger signal to the immune system. The education of the immune system to distinguish self from non-self is mainly carried out in the thymus and gives rise to central tolerance, whereas the ability to sense a danger or a healthy tissue constitutes peripheral tolerance. In these studies we have investigated the peripheral tolerance mechanisms controlled by the autoimmune regulator (Aire) gene in Aire deficient mice, an animal model of the monogenic disease autoimmune polyendocrine syndrome type I (APS I). Aire-/- mice displayed increased numbers of myeloid-derived antigen-presenting cells (APCs) in the spleen, lymph nodes and peritoneum as well as more blood monocytes and metallophilic macrophages in the spleen. Monocytes were also increased in the blood of APS I patients. Monocyte precursors displayed an accelerated development in the bone marrow of Aire-/- mice, and Aire-/- APCs had an altered phenotype that caused an increased immune response in several different contexts. Aire-/- splenic and lymph node dendritic cells had an increased ability to activate naive T cells, partly as a result of an upregulated expression of the costimulatory molecule VCAM-1. In Aire-/- mice increased activity of the metallophilic macrophages in the splenic marginal zone seems to be responsible both for the activated phenotype of marginal zone B cells and for the frequent development of marginal zone lymphoma with aging. In a TCR transgenic model Aire deficiency caused an increased superantigen-mediated TCR revision in the spleen, perhaps as a result of the altered phenotype of APCs in the spleen. Finally, Aire was shown to influence autoimmune disease development by a macrophage-dependent mechanism in diabetes induced with multiple low dose streptozotocin injections. These results indicate that Aire has an important function in peripheral tolerance by controlling the phenotype of myeloid-derived APCs and thereby regulating the activation of T and B lymphocytes.