Imunofenotipagem dos linfócitos positivos para indoleamina 2, 3 dioxigenase (IDO) em cultura de células de placenta bovina / Phenotyping of the indoleamine 2, 3 dioxygenase (IDO) positive lymphocytes in bovine placental cell culture

A gestação é um estado fisiológico que exige adaptações imunológicas para que transcorra normalmente. Nesse período a mãe e o feto apresentam uma relação imunológica, ou seja, a interface materno fetal. A enzima indoleamina 2,3 dioxigenase (IDO) desempenha um papel importante na tolerância materno fetal, por ser responsável pela metabolização do triptofano, impedindo por diversas vias a proliferação principalmente de linfócitos TCD8. Diversos tipos celulares estão presentes na interface materno fetal e vários deles podem expressar a IDO. Os leucócitos com perfil Th1 produzem uma citocina conhecida: o interferon γ que estimula a expressão da IDO em vários tipos celulares. Os linfócitos são divididos em subpopulações de acordo com sua função e fenótipo. Seus tipos incluem linfócitos T, linfócitos B e as células natural killer (NK). Hormônios também atuam nesse processo a progesterona que exerce função determinante sobre a resposta imunológica materna podendo alterar o prognóstico gestacional e o estrógeno essencial para a tolerância materno fetal e manutenção da prenhez. Dessa maneira este trabalho tem por objetivo principal identificar os linfócitos presentes na placenta bovina em cultivo que expressam IDO (linfócitos T, linfócitos B e células NK), frente a estimulação por progesterona, estrógeno e interferon γ nas diversas fases gestacionais utilizando a citometria de fluxo. Segundo os resultados no período de 67,5 a 77, 5 dias com a adição de interferon γ a expressão da enzima IDO aumentou discretamente nos linfócitos TCD3, TCD4, e diferente dos linfócitos T CD8 apresentaram uma elevada expressão da enzima (4,48 ± 2,12 - 8,65± 4,91)....

Pregnancy is a physiological state that requires immune adaptation in order to be successfully carried on. During this period, mother and fetus establish an immune tolerance status at the maternal fetal interface. Indoleamine 2,3-dioxygenase (IDO) plays an important role in maternal-fetal tolerance by metabolizing tryptophan, impairs by several pathways, mainly T CD8 cells proliferation. Several cell types are present in the maternal fetal interface and several of them can express IDO. Leucocytes with Th1 produce a cytokine known as interferon γ that stimulates the expression of IDO in several cell types. Lymphocytes are divided into sub-populations according to their function and phenotype: T lymphocytes, B lymphocytes and natural killer cells (NK). Hormones also involved in this process where progesterone exerts decisive role on maternal immune response that may change gestational outcome and estrogen is essential for fetal maternal tolerance and maintenance of pregnancy. Therefore, the main objective of this study was to identify lymphocytes in the bovine placental cell culture that are sensitive to progesterone, estrogen and interferon γ, IDO expression in various gestational stages using flow cytometry. According to the results in the gestational period from 67.5 to 77.5 days with the addition of interferon γ expression IDO was slightly increased in TCD3 lymphocytes, CD4, and differently from the other T cells CD8 displayed an higher expression of the enzyme (4.48±2.12 to 8.65±4.91)...

Vascular endothelial growth factor-A enhances indoleamine 2,3-dioxygenase expression by dendritic cells and subsequently impacts lymphocyte proliferation

Dendritic cells (DCs) are antigen (Ag)-presenting cells that activate and stimulate effective immune responses by T cells, but can also act as negative regulators of these responses and thus play important roles in immune regulation. Pro-angiogenic vascular endothelial growth factor (VEGF) has been shown to cause defective DC differentiation and maturation. Previous studies have demonstrated that the addition of VEGF to DC cultures renders these cells weak stimulators of Ag-specific T cells due to the inhibitory effects mediated by VEGF receptor 1 (VEGFR1) and/or VEGFR2 signalling. As the enzyme indoleamine 2,3-dioxygenase (IDO) is recognised as an important negative regulator of immune responses, this study aimed to investigate whether VEGF affects the expression of IDO by DCs and whether VEGF-matured DCs acquire a suppressor phenotype. Our results are the first to demonstrate that VEGF increases the expression and activity of IDO in DCs, which has a suppressive effect on Ag-specific and mitogen-stimulated lymphocyte proliferation. These mechanisms have broad implications for the study of immunological responses and tolerance under conditions as diverse as cancer, graft rejection and autoimmunity.

Regulatory T cells: A review.

Regulatory T cells (Tregs) play a pivotal role in the homeostasis of the immune system and in the modulation of the immune response. Tregs have emerged as key players in the development and maintenance of peripheral immune tolerance. Broadly speaking, CD4+ T cells possessing the ability to suppress immune responses can be divided into two types: naturally occurring (nTreg) and inducible (iTreg) or adaptive regulatory cells. Naturally occurring thymus-derived CD4+CD25+ Tregs are a subset of T cells which have immunosuppressive properties and are 5%–10% of the total peripheral CD4+ T cells. In normal conditions, Tregs regulate ongoing immune responses and prevent autoimmunity. Imbalanced function or number of these cells, either enhanced or decreased, might lead to tumour development and autoimmunity, respectively. These cells thus play a major role in autoimmune diseases, transplantation tolerance, infectious diseases, allergic disease and tumour immunity. These natural properties make Tregs attractive tools for novel immunotherapeutic approaches. The in vivo manipulation or depletion of Tregs may help devise effective immunotherapy for patients with cancer, autoimmunity, graftversus- host disease, infectious diseases and allergic diseases. It is crucial to understand the biology of Tregs before attempting therapies, including (i) the injection of expanded Tregs to cure autoimmune disease or prevent graft-versus-host disease or (ii) the depletion or inhibition of Tregs in cancer therapy. Recent findings in murine models and studies in humans have opened new avenues to study the biology of Tregs and their therapeutic potential. This overview provides a framework for integrating these concepts of basic and translational research.

Manifestações clínicas e evolução da infecção pelo vírus da influenza A (H1N1) em receptores de transplante renal / Clinical manifestations and evolution of infection by influenza A (H1N1) in kidney transplant recipients

INTRODUÇÃO: A emergência do surto pandêmico de influenza A, subtipo H1N1, em abril de 2009, representou um grande desafio para a logística de saúde pública. Embora a maioria dos pacientes infectados apresente manifestações clínicas e evolutivas muito semelhantes às observadas na influenza sazonal, um número significativo de indivíduos evolui com pneumonia e insuficiência respiratória aguda severa. O impacto da infecção pelo vírus influenza A, subtipo H1N1, em pacientes imunossuprimidos não é determinado. MÉTODOS: Neste estudo, foram analisadas a apresentação clínica e a evolução da influenza A, subtipo H1N1, em 19 receptores de transplante renal. Os pacientes receberam confirmação diagnóstica pela técnica de RT-PCR. O manejo clínico incluiu terapêutica antiviral com fosfato de oseltamivir e antibióticos. RESULTADOS: A população estudada foi predominantemente de indivíduos do sexo masculino (79 por cento), brancos (63 por cento), com idade média de 38,6 ± 17 anos e portadores de pelo menos uma comorbidade (53 por cento). A infecção por influenza A, subtipo H1N1, foi diagnosticada em média 41,6 ± 49,6 meses após o transplante. Os sintomas mais comuns foram: tosse (100 por cento), febre (84 por cento), dispneia (79 por cento) e mialgia (42 por cento). Disfunção aguda do enxerto foi observada em 42 por cento dos pacientes. Cinco pacientes (26 por cento) foram admitidos em Unidade de Terapia Intensiva, dois (10 por cento) necessitaram de suporte com ventilação invasiva e dois (10 por cento) receberam drogas vasoativas. A mortalidade foi de 10 por cento. CONCLUSÕES: A disfunção aguda do enxerto renal foi um achado frequente, e as características clínicas, laboratoriais e evolutivas foram comparáveis às da população geral.

INTRODUCTION: The emergence of the pan>demic outbreak of influenza A (H1N1) in April, 2009, represented a logistic challenge for public health. Although most infected patients presented clinical and evolutionary manifestations which were very similar to seasonal influenza, a significant number of individuals developed pneumonia and severe acute respiratory failure. The impact of influenza A (H1N1) in immunocompromised patients is not well established yet. METHODS: This study aimed to analyze the clinical presentations and evolution of influenza A (H1N1) in 19 kidney transplant recipients. Influenza A (H1N1) infection was confirmed by RT-PCR in all patients. Treatment included antiviral therapy with oseltamivir phosphate and antibiotics. RESULTS: The studied population was compounded mostly of white people (63 percent), males (79 percent), at a mean age of 38.6 ± 17 years and patients with at least one comorbidity (53 percent). Influenza A (H1N1) infection was identified 41.6 ± 49.6 months after transplantation. Common symptoms included cough (100 percent), fever (84 percent), dyspnea (79 percent), and myalgia (42 percent). Acute allograft dysfunction was observed in 42 percent of the patients. Five patients (26 percent) were admitted to the Intensive Care Unit, two (10 percent) required invasive ventilation support, and two (10 percent) required vasoactive drugs. Mortality rate was 10 percent. CONCLUSIONS: Acute renal allograft dysfunction was a common finding. Clinical, laboratory, and evolutionary characteristics were comparable to those in the general population.

El embarazo humano: paradigma biológico de tolerancia y adaptación / Human pregnancy, a biological paradigm of tolerance and adaptation

This review analyses the changes in immunological tolerance, and the systemic and local hemodynamic changes observed along human pregnancy. To underscore the conceptual importance of tolerance and adaptation the background isprovided by the two main advocates ofthese ideas: Gandhi and Darwin. The cognate factors that determine immunological tolerance (IT), systemic (SA) and local adaptation (LA) are múltiple; IT = desensitisation to paternal antigens, absence of HLA-A, roles of HLA-G, natural killer cells and their receptors; SA = decreased vascular resistance, plasma volume expansión, increased cardiac output and plasma renin activity; LA = prostacyclin, nitric oxide, kallikrein-kinin system, vasodilator arm of the renin angiotensin system, vascular endothelial growth factor (VEGF). A possible role of vasodilators in the crucial process of trophoblast invasión and uterine artery transformation is supported. The relevance ofan adequate adaptation to pregnancy is highlighted not only by the intragestational complications derivedfrom a defective process, such as intrauterine growth restriction, preterm birth, and preeclampsia -its foremost expression- but also by the long term cardiovascular complications ofthe mother and her offspring.

A imunofisiopatologia da autoimunidade / Immunophysiopathology of autoimmunity

Este artigo visa explicar conceitos básicos de imunologia de forma clara e sucinta para expor a fisiopatologia das síndromes autoimunes através de exemplos clínicos e/ou experimentais. Esperamos assim esclarecer pontos-chaves que contribuem para a instalação destas patologias.

Rol de las células T regulatorias en esclerosis múltiple / Role of T-regulatory cells in multiple sclerosis

La esclerosis múltiple (EM) es una enfermedad inflamatoria autoinmune desmielinizante del sistema nervioso central (SNC). La mayoría de las enfermedades autoinmunes se originan por la activación anormal de la respuesta inflamatoria contra auto-antígenos (la mayoría de ellos desconocidos a la fecha) como consecuencia de la pérdida de la tolerancia periférica. Las células T-regulatorias constituyen un grupo esencial de linfocitos T encargados del mantenimiento de la tolerancia periférica, la prevención de enfermedades autoinmunes y la limitación de enfermedades inflamatorias crónicas. Teniendo en cuenta la importancia de la tolerancia periférica, las células T-regulatorias serían componentes cruciales en el escenario fisiopatológico de los procesos autoinmunes, incluyendo la EM. El presente trabajo recopila los conocimientos actuales sobre la función de las células T-regulatorias en la EM, la enfermedad autoinmune desmielinizante del SNC más prevalente en los seres humanos.

Multiple sclerosis (MS) is an autoimmune inflammatory demyelinating disease of the central nervous system (CNS). Most of autoimmune diseases arise by an abnormal activation of the inflammatory response against self-antigens (most of them unknown up to date) as a consequence of dysfunction in peripheral tolerance. Regulatory T-cells are essential for maintaining peripheral tolerance, preventing autoimmune diseases and limiting chronic inflammatory conditions. Based on that knowledge, T-regulatory cells have emerged as a key component of the physiopathology of autoimmune diseases including MS. This review compiles the current knowledge on the role and function of T-regulatory cells in MS, the most prevalent CNS autoimmune disease in humans.

Condição imunológica de bovinos das raças Holandesa e Nelore frente a Babesia bovis e B. bigemina em duas regiões do Estado de São Paulo / Immunological condition of cattle in Holstein and Nelore breed in regard to Babesia bovis and B. bigemina in two regions of the State of São Paulo

A resposta imunológica de uma população frente a um agente infeccioso pode variar entre as raças e o manejo dessa população. Dessa maneira, torna-se relevante a pesquisa regional, visando o conhecimento da inter-relação do agente com seu hospedeiro. Partindo desses pressupostos, investigou-se a ocorrência de imunoglobulinas da classe IgG, anti-Babesia bovis e anti-B. bigemina nas raças Nelore (Bos indicus) e Holandesa (Bos taurus), em duas regiões do Estado de São Paulo, distantes a 300 km. Pelo método de ELISA indireto, foram testadas 1.161 amostras de soro de bovinos. As freqüências médias de anticorpos mostraram que ambas as regiões se encontram em situação de estabilidade enzoótica para B. bovis para ambas as raças estudadas, embora haja tendência para área marginal na região de Presidente Prudente para raça Nelore. No referente a B. bigemina ambas as regiões são de estabilidade enzoótica para a raça Holandesa e de instabilidade enzoótica para a raça Nelore. Essa constatação é um alerta sanitário, pois casos agudos da doença ou surtos específicos de B. bigemina na raça Nelore podem ocorrer nessas regiões.

The immunological reply of a population to an infectious agent can vary between races and handling of this population. Regional research becomes important, in order to know the interrelation between the agent and its host. In this way, the occurrence of immunoglobulins of class G, anti-Babesia bovis and anti-Babesia bigemina in the Nelore (Bos indicus) and Hostein breed (Bos taurus), was investigated in two regions of the State of São Paulo, 300 km distant from each other. For the indirect method of ELISA, 1,161 bovine serum samples were tested. The medium frequencies of antibodies showed that in the two regions exists an enzootic stability for B. bovis in both breeds studied; even so there was a tendency of marginal area for the Nelore breed in one of the regions. Regarding B. bigemina, in both regions exists enzootic stability for the Hostein and enzootic instability for the Nelore breed. Therefore, acute cases of the disease or specific outbreaks by B. bigemina infection in the Nelore breed may occur in these regions.

Maintenance of CD8+T-cell anergy by CD4+CD25+ regulatory T cells in chronic graft-versus-host disease

In a murine model of systemic lupus erythematosus (SLE)-like chronic graft-versus-host disease (cGVHD), donor CD8+T cells rapidly fall into anergy to host cells, while donor CD4+T cells hyperactivate B cells and break B-cell tolerance to self-Ags in the recipient mouse. The functional recovery of donor CD8+T cells can result in the conversion of cGVHD to acute GVHD (aGVHD), indicating that donor CD8+T-cell anergy is a restriction factor in the development of cGVHD. In this report, we present evidence that donor CD4+CD25+regulatory T cells (T(reg) cells) are critical in maintaining the donor CD8+T-cell anergy and thus suppressing the development of aGVHD in mice that are naturally prone to cGVHD. Our results provide a novel insight into the role of T(reg) cells in determining cGVHD versus aGVHD.

Células dendríticas como determinantes del equilibrio entre inmunidad y autoinmunidad / Dendritic cells like determinants of the balance between immunity and autoimmunity

Autoinmune diseases occur when the immunological system loses its capability to recognize between self and foreign, and develops a response against healthy tissues. Both molecular bases that trigger these pathologies and genetic factors of susceptibility are unknown. Identification of these factors is fundamental for understanding and developing specific therapies for autoimmune diseases. Dendritic cells (DCs) - professional antigen presenting cells - play a fundamental roll in the development and modulation of the acquired immune response because they have the unique capacity to active naïve T lymphocytes. In order to activate T lymphocytes, the DCs must supply simultaneously two molecular signals which correspond to the antigen (or peptid complex MHC) plus costimulating signals. In absence of costimulation, the DCs induce inactivation of T lymphocytes, mechanism by which they are able to maintain peripheral tolerance against self antigens. In this way, it has been proposed that the immature DCs present antigens in absence of costimulation and provoke tolerance. On the contrary, mature DCs present antigens together with costimulating signals, which lead to immunity. In self-immune diseases, the process of tolerance in the presence of autoantigens could be deficient due to alterations in the normal function of DCs. One of the causes of this defect could be that there is an unbalance in the expression of activating and inhibiting Fcy receptors on the surface of DCs. This would generate DCs with a constitutive phenotype of maturity that would interfere with its tolerogenic activity, and would favor the permanent activation of T lymphocytes, including those that are autoreactive.

La tolerancia (T) en el trasplante renal (TR) / The toleance (T) in the kidney transplantation (KT)

La tolerancia (T) renal, desde el punto de vista inmunológico es la ausencia total de respuesta inmunitaria, en el receptor (R) cuando se coloca un injerto renal, por ausencia de clonas reactivas generadas por los linfocitos T (LT) del R contra antígenos (ag) del donador (D). Esta T total, en ausencia de inmunosupresores (IS) o de otros productos biológicos, es un ideal terapéutico: un "Santo Grial" inaccesible, excepto en algunos casos comunicados de trasplante renal (TR) entre gemelos univitelinos, cuyos sistemas inmunes en MHC (Major Hystocompatibility Complex) o de HLA (Human Leukocyte Antigen) y en otros secundarios, son idénticos, tanto en el D como en el R. Tratándose de alotrasplantes: D y R con diferencias inmunológicas, siempre se requerirán IS, al menos hasta la fecha, para mantener un estado de T activa, con el menor daño inmunológico posible contra el TR. En el presente trabajo se buscará presentar en forma suscinta los procedimientos actuales de inducción de T inmune y las futuras posibilidades terapéuticas de inducción de nuevos procedimientos terapéuticos, muchos de ellos, aún en fase experimental, con la esperanza de alcanzar a la larga el ideal de la T total.

Avances en el estudio de los mecanismos celulares de supresión de la respuesta inmunitaria en la tuberculosis / Advances in the study of immunosuppression cell mechanisms in tuberculosis

La respuesta inmunitaria protectora generada durante la tuberculosis es el resultado de la integración de las respuestas inmunitarias, natural y adquirida, a través de la activación de linfocitos T CD4+ productores de IFN-g, permitiendo la eliminación del bacilo por macrófagos activados. La inmunosupresión, es la consecuencia de un desequilibrio en la respuesta inmunitaria con progreso de la infección. En este trabajo, se revisan las características de la respuesta inmunitaria contra Mycobacterium tuberculosis así como los mecanismos celulares de supresión de la respuesta inmunitaria.

Oral tolerance induction with altered forms of ovalbumin

As a T cell-dependent phenomenon, oral tolerance is not expected to depend necessarily on native configuration of antigens. We investigated the induction of oral tolerance with modified ovalbumin (Ova). Oral administration of heat-denatured (HD-Ova) and cyanogen bromide-degraded ovalbumin was less effective than native Ova in inducing oral tolerance in B6D2F1 mice. HD-Ova was effective in suppressing delayed-type hypersensitivity (DTH) reactions but did not suppress specific antibody formation. Injection of Ova directly into the stomach, but not into the ileum or cecum, suppressed subsequent immunization to DTH reactions. Gavage with protease inhibitors (aprotinin or ovomucoid) before gavage with Ova was ineffective in blocking tolerance induction. Treatment with hydroxyurea to destroy cycling cells 24 h before gavage with Ova blocked oral tolerance induction and also the possibility to passively transfer tolerance to naive recipients with tehe serum of mice gavaged with Ova 1 h before. The implications of these findings about oral tolerance induction are discussed.

Aging and immunoglobulin isotype patterns in oral tolerance

In the present review we address oral tolerance as an important biological phenomenon and discuss how it is affected by aging. Other factors such as frequency of feeding and previous digestion of the antigen also seem to influence the establishment of oral tolerance. We also analyze immunoglobulin isotypes of specific antibodies formed by tolerant and immunized animals of different ages submitted to different conditions of oral antigen administration. Isotypic patterns were studied as a parameter for assessing the pathways of B and T cell interactions leading to antibody production.

Aloinmunización transplacentaria por antígenos plaquetarios específicos: prevalencia y características en una población chilena / Transplacental alloimmunization against platelet antigens: prevalence and features in a chilean population

Backgrour: Neonatal alloimmune thrombocytopenia (NAIT) is a result of fetomaternal incompatibility. Platelet destruction is caused by a maternal alntibody directed against a fetal platelet antigen inherited from the father and lacking on the mother's platelets. The incidence and features of transplacental alloimmunization depend on the frequency of expression of platelet specific antigens, which are highly variable among different populations. Aim: To determine the prevalence and characteristics of transplacental alloimmunization in a large, group of pregnant women in Chile. Material and methods: We, studied 3,041 samples obtained during the third trimester of gestation. In all samples, anti platelet antibodies were screened by ELISA with platelet membranes fixed to a microtiter plate. Positive samples were further studied for antigenic specificity with the monoclonal antibody specific immobilization of platelet antigens (MAIPA) test. Results: Anti platelet antibodies were found in 261 samples (8.5 percent). The MAIPA test identified 6 samples with antibodies directed against major platelet membrane glycoproteins, 2 anti GPIb, 2 anti GPIIb/IIIa and 2 anti GPIa/IIIa. In four cases, anti HLA antibodies coexisted. Two cases corresponded to well defined platelet antigen systems: one anti HPA-1a and one anti HPA-5b. No clinical evidence of thrombocytopenia of the newborn was detected in all these cases with anti GP antibodies. Conclusions: A prevalence of platelet specific antibodies of 0.2 por ciento with only one anti HPA-1a was detected. These findings are in contrast with those of other populations but in accordance with the low frequency of the HPA-1b/b phenotype in the Chilean population. The very low incidence of platelet specific antibodies and the lack of association with clinical thrombocytopenia in the newborn, do not support the recommendation of routine antenatal screening to all women in Chile

Melatonina / Melatonin

Se revisan las principales acciones fisiológicas de la melatonina, destacando sus efectos metabólicos y endocrinológicos y sus influencias sobre el sistema nervioso y el inmunológico. Se señalan los factores que estimulan la secreción de la melatonina en la glándula pineal. Entre ellos destaca la oscuridad, por lo que la melatonina ha sido considerada como el mensajero de la noche y la reguladora de los ritmos circadianos. Se señalan igualmente los posibles usos terapéuticos de la melatonina, de los cuales el más importante hasta ahora es la regulación del ciclo vigilia-sueño y la prevención del jet-lag. Por el momento se discuten sus eventuales proyecciones terapéuticas derivadas de efectos antioxidantes; inmunomoduladores y cardioprotectores. Los efectos laterales indeseables son muy escasos con la dosis habituales de 3 a 10 mg

Mecanismos gerais de tolerância imunológica e auto-imunidade / General mechanisms of immunologic tolerance and autoimmunity

A tolerância imunológica a antígenos próprios do organismo é um estado fisiológico, adquirido ao longo do desenvolvimento, envolvendo vários mecanismos, para preservar os tecidos do indivíduo. Ambos repertórios, de linfócitos T e B, sao tolerizados por mecanismos interconectados, que ocorrem em dois níveis: 1) órgaos linfóides primários (tolerância central), e 2) órgaos linfóides periféricos e sangue circulante (tolerância periférica). A deleçao, por apoptose, de clones Te B imaturos, em timo e medula óssea, respectivamente, constitui o principal mecanismo de tolerância, através da seleçao negativa de células com potencial de auto-reatividade. Este processo é influenciado por diversos fatores: grau de afinidade, pelo ligando, do receptor específico para o antígeno, dos linfócitos T e B; concentraçao e natureza do antígeno reconhecido; interaçao de co-receptores e de moléculas de adesao. A detecçao de clones T e B auto-reativos, no repertório periférico normal, confirma a possibilidade de escape à deleçao clonal. Por um lado, linfócitos maduros podem ser potencialmente auto-agressivos, e ainda tolerizados, em periferia, através de mecanismos descritos principalmente para o compartimento T: deleçao clonal, anergia clonal (ocupaçao do receptor, em ausência de co-estimulaçao) e imunossupressao (por células ou citocínas). Por outro lado, o conceito de auto-reatividade fisiológica é introduzido, para se diferenciar de doença auto-imune (auto-reatividade patológica). As doenças auto-imunes se desenvolvem por falhas na manutençao da tolerância, cujas causas sao múltiplas: terreno genético individual, sobretudo genes que regulam a apresentaçao e reconhecimento antigênicos, e fatores ambientais (dieta, infecçoes virais ou bacterianas).