Gut: Key Element on Immune System Regulation

Abstract The gut is the main organ that mediates the contact between antigens with our organism, controlling the immune response against environmental factors, such as microbiota and food. Innate lymphoid cells participate in the gut-associated lymphoid tissue (GALT) maturation during the prenatal and early postnatal periods. After birth, breast milk provides the essential elements for the continuity of development of this tissue, leading to structural changes and healthy microbiota installation. The microbiota participates in the organogenesis of the GALT, as in the formation of intestinal villi, stimulating the proliferation of stem cells and maintaining the integrity of epithelial barrier. Foods are also involved in maturation of the GALT, where the protein source depletion reduced the number of resident lymphocytes. This unique microenvironment present in the intestinal lamina propria (LP) and mesenteric lymph nodes (mLN) induce tolerance to innocuous antigens from the diet, known as Oral Tolerance. Antigens sampled by intestinal epithelium cells are transferred to specialized dendritic cells, residing in the LP, which migrate to the mesenteric lymph nodes where they participate in the induction of regulatory T cells (Treg). Understanding these phenomena may establish the intestinal mucosa as a tool in therapy of inflammatory bowel diseases and immunological disorders.

Emerging Roles of Lymphatic Vasculature in Immunity

The lymphatic vasculature has been regarded as a passive conduit for interstitial fluid and responsible for the absorption of macromolecules such as proteins or lipids and transport of nutrients from food. However, emerging data show that the lymphatic vasculature system plays an important role in immune modulation. One of its major roles is to coordinate antigen transport and immune-cell trafficking from peripheral tissues to secondary lymphoid organs, lymph nodes. This perspective was recently updated with the notion that the interaction between lymphatic endothelial cells and leukocytes controls the immune-cell migration and immune responses by regulating lymphatic flow and various secreted molecules such as chemokines and cytokines. In this review, we introduce the lymphatic vasculature networks and genetic transgenic models for research on the lymphatic vasculature system. Next, we discuss the contribution of lymphatic endothelial cells to the control of immune-cell trafficking and to maintenance of peripheral tolerance. Finally, the physiological roles and features of the lymphatic vasculature system are further discussed regarding inflammation-induced lymphangiogenesis in a pathological condition, especially in mucosal tissues such as the gastrointestinal tract and respiratory tract.

Role of Regulatory Cells in Oral Tolerance

The immune system is continuously exposed to great amounts of different antigens from both food and intestinal microbes. Immune tolerance to these antigens is very important for intestinal and systemic immune homeostasis. Oral tolerance is a specific type of peripheral tolerance induced by exposure to antigen via the oral route. Investigations on the role of intestinal immune system in preventing hypersensitivity reactions to innocuous dietary and microbial antigens have been intensively performed during the last 2 decades. In this review article, we discuss how food allergens are recognized by the intestinal immune system and draw attention to the role of regulatory T (Treg) and B (Breg) cells in the establishment of oral tolerance and tolerogenic features of intestinal dendritic cells. We also emphasize the potential role of tonsils in oral tolerance induction because of their anatomical location, cellular composition, and possible usage to develop novel ways of specific immunotherapy for the treatment of allergic diseases.

Relationship between percentage of regulatory t-cells and dental amalgam fillings / Relación entre el porcentaje de células t-reguladoras y obturaciones de amalgama

Abstract: introduction: regulatory T-cells are the main component of peripheral tolerance and their level is decreased in autoimmunity. In dental amalgam, a mixture of metals is used as a restorative material. During daily a ctivities, these metals are ingested and affect renal, neurosensory and immune systems. Studies have demonstrated an increased risk of autoimmune diseases in patients with dental amalgam fillings. It was hypothesized that the percentage of regulatory T-cells decreases in individuals with amalgam fillings. Therefore this study was designed to determine and compare the percentage of regulatory T-cells in individuals with and without amalgam fillings. Material and Methods: This was a cross-sectional study. Subjects were divided into two groups with each group consisting of 40 individuals. Group I (study group) comprised individuals with amalgam fillings, and Group II (control group), individuals without amalgam fillings in their teeth. Blood samples of all the participants were collected and tagged with CD4 FITC, CD25 PE and CD127 PerCP-Cy monoclonal antibodies for the detection of regulatory T-cells, FACSCalibur was used for this purpose. Results: The percentage of regulatory T-cells in the control group was high (77.77 +/- 5.54 percent) compared to the study group (76.09 +/- 7.68 percent), however, on comparison, the difference was not statistically significant (p=0.25). Conclusion: Dental amalgam fillings did not show a declining effect on the percentage of regulatory T-cells.

Resumen: introducción: las células T reguladoras son el principal componente de la tolerancia periférica y su nivel se reduce en la autoinmunidad. En las obturaciones de amalgama, una mezcla de metales se utiliza como un material de restauración. Durante las actividades diarias, estos metales se ingieren y afectan el sistema renal, neurosensorial e inmunológico. Los estudios han demostrado un aumento del riesgo de enfermedades autoinmunes en pacientes con amalgamas dentales. Se planteó la hipótesis que el porcentaje de células T reguladoras disminuye en individuos con obturaciones de amalgama. Por tanto, este estudio fue diseñado para determinar y comparar el porcentaje de células T reguladoras en individuos con y sin obturaciones de amalgama. Material y Métodos: Se realizó un estudio de corte transversal. Los sujetos fueron divididos en dos grupos, cada uno con 40 individuos. El grupo I (de estudio) estuvo conformado por individuos con obturaciones de amalgama y el grupo II (de control) por individuos sin obturaciones de amalgma. Se colectaron muestras de sangre, las que fueron marcadas con anticuerpos monoclonales CD4 FITC, CD25 PE y CD127 PerCP-C para detectar las células T reguladoras, se utilizó FACSCalibur para este propósito. Resultados: El porcentaje de células T reguladoras en el grupo control fue alta (77,77 +/- 5,54 por ciento) en comparación con el grupo de estudio (76,09 +/- 7,68 por ciento), pero esta diferencia no fue estadísticamente significativa (p=0,25). Conclusión: Las obturaciones de amalgama no se asociaron con una disminución en el porcentaje de células T reguladoras.

Immunomodulatory Function of Mesenchymal Stem Cells for Rheumatoid Arthritis

Developments in our comprehension of the autoimmune and inflammation mechanisms in rheumatoid arthritis (RA) have produced targeted therapies that block aberrant immune cells and cytokine networks, and improved treatment of RA patients considerably. Nevertheless, limitations of these treatments include incomplete treatment response, adverse effects requiring drug withdrawal, and refractory cases. Hence, many researchers have redirected efforts towards investigation of other biological aspects of RA, including the mechanisms driving joint tissue repair and balanced immune regulation. This investigation focuses on mesenchymal stem cell (MSC) research, with the ultimate goal of developing interventions for immune modulation and repair of damaged joints. MSCs are multipotent cells capable of differentiating into mesodermal lineage cells. These cells have also attracted interest for their anti-inflammatory and immunomodulatory capacities. They have many distinctive immunological properties, inhibiting the proliferation and production of cytokines by T, B, natural killer, and dendritic cells. Indeed, MSCs have the capacity to regulate immunity-induced peripheral tolerance, suggesting they can be used as therapeutic tools in RA. This review discusses properties of MSCs, in vitro studies, animal studies, and clinical trials involving MSCs. Our review discusses the current knowledge of the mechanisms of MSC-mediated immunosuppression and potential therapeutic uses of MSCs in RA.

Development of Auto Antigen-specific Regulatory T Cells for Diabetes Immunotherapy

CD4⁺ regulatory T cells (Tregs) are essential for normal immune surveillance, and their dysfunction can lead to the development of autoimmune diseases, such as type-1 diabetes (T1D). T1D is a T cell-mediated autoimmune disease characterized by islet β cell destruction, hypoinsulinemia, and severely altered glucose homeostasis. Tregs play a critical role in the development of T1D and participate in peripheral tolerance. Pluripotent stem cells (PSCs) can be utilized to obtain a renewable source of healthy Tregs to treat T1D as they have the ability to produce almost all cell types in the body, including Tregs. However, the right conditions for the development of antigen (Ag)-specific Tregs from PSCs (i.e., PSC-Tregs) remain undefined, especially molecular mechanisms that direct differentiation of such Tregs. Auto Ag-specific PSC-Tregs can be programmed to be tissue-associated and infiltrate to local inflamed tissue (e.g., islets) to suppress autoimmune responses after adoptive transfer, thereby avoiding potential overall immunosuppression from non-specific Tregs. Developing auto Ag-specific PSC-Tregs can reduce overall immunosuppression after adoptive transfer by accumulating inflamed islets, which drives forward the use of therapeutic PSC-Tregs for cell-based therapies in T1D.

Development of Auto Antigen-specific Regulatory T Cells for Diabetes Immunotherapy

CD4⁺ regulatory T cells (Tregs) are essential for normal immune surveillance, and their dysfunction can lead to the development of autoimmune diseases, such as type-1 diabetes (T1D). T1D is a T cell-mediated autoimmune disease characterized by islet β cell destruction, hypoinsulinemia, and severely altered glucose homeostasis. Tregs play a critical role in the development of T1D and participate in peripheral tolerance. Pluripotent stem cells (PSCs) can be utilized to obtain a renewable source of healthy Tregs to treat T1D as they have the ability to produce almost all cell types in the body, including Tregs. However, the right conditions for the development of antigen (Ag)-specific Tregs from PSCs (i.e., PSC-Tregs) remain undefined, especially molecular mechanisms that direct differentiation of such Tregs. Auto Ag-specific PSC-Tregs can be programmed to be tissue-associated and infiltrate to local inflamed tissue (e.g., islets) to suppress autoimmune responses after adoptive transfer, thereby avoiding potential overall immunosuppression from non-specific Tregs. Developing auto Ag-specific PSC-Tregs can reduce overall immunosuppression after adoptive transfer by accumulating inflamed islets, which drives forward the use of therapeutic PSC-Tregs for cell-based therapies in T1D.

Germinal Center Formation Controlled by Balancing Between Follicular Helper T Cells and Follicular Regulatory T Cells / 한양의대학술지

Follicular helper T cells (Tfh) play a significant role in providing T cell help to B cells during the germinal center reaction, where somatic hypermutation, affinity maturation, isotype class switching, and the differentiation of memory B cells and long-lived plasma cells occur. Antigen-specific T cells with IL-6 and IL-21 upregulate CXCR5, which is required for the migration of T cells into B cell follicles, where these T cells mature into Tfh. The surface markers including PD-1, ICOS, and CD40L play a significant role in providing T cell help to B cells. The upregulation of transcription factor Bcl-6 induces the expression of CXCR5, which is an important factor for Tfh differentiation, by inhibiting the expression of other lineage-specific transcription factors such as T-bet, GATA3, and RORgammat. Surprisingly, recent evidence suggests that CD4 T cells already committed to Th1, Th2, and Th17 cells obtain flexibility in their differentiation programs by downregulating T-bet, GATA3, and RORgammat, upregulating Bcl-6 and thus convert into Tfh. Limiting the numbers of Tfh within germinal centers is important in the regulation of the autoantibody production that is central to autoimmune diseases. Recently, it was revealed that the germinal center reaction and the size of the Tfh population are also regulated by thymus-derived follicular regulatory T cells (Tfr) expressing CXCR5 and Foxp3. Dysregulation of Tfh appears to be a pathogenic cause of autoimmune disease suggesting that tight regulation of Tfh and germinal center reaction by Tfr is essential for maintaining immune tolerance. Therefore, the balance between Tfh and Tfr appears to be a critical peripheral tolerance mechanism that can inhibit autoimmune disorders.

Novel Pharmacologic Therapies in the Treatment of Systemic Lupus Erythematosus / 한양의대학술지

Systemic lupus erythematosus (lupus) is an autoimmune disease that affects primarily women, especially those of reproductive age. Lupus is a prototypic organ non-specific autoimmune disease that may affect any organ in the body resulting in displaying a broad spectrum of clinical and immunological manifestations. The pathogenesis of lupus involves a complex interplay between genetic and environmental factors and the adaptive and innate immune systems. Defects in central and peripheral tolerance, increased antigenic load, excess T-cell help, B cell hyperactivity, autoantibody production and cytokine imbalance, ultimately lead to immune-complex formation and complement activation causing immunologically mediated organ damage, culminating in premature death. There is an urgent need for the development of novel agents since many patients are refractory to traditional agents. However, there are two hurdles that make development of new therapeutic agents difficult. First, we do not understand the whole picture of the pathogenesis of lupus because of its complex and multi-systemic presentation. Secondly, lupus lacks a reliable and sensitive biomarker for measuring disease activity, and a standardized method for defining response to therapy. Nevertheless, great advances have been made during the past 10 years because of the great efforts of basic researchers and clinicians on elucidating the cause of the disease, and participation of pharmaceutical and biotechnical companies in the development of novel agents. My goal was to evaluate the efficacy and safety of novel pharmaceutical agents by a comprehensive review of open-label and randomized clinical trials conducted in patients with lupus.

The Role of MicroRNAs in Regulatory T Cells and in the Immune Response

The discovery of microRNA (miRNA) is one of the major scientific breakthroughs in recent years and has revolutionized current cell biology and medical science. miRNAs are small (19~25nt) noncoding RNA molecules that post-transcriptionally regulate gene expression by targeting the 3' untranslated region (3'UTR) of specific messenger RNAs (mRNAs) for degradation of translation repression. Genetic ablation of the miRNA machinery, as well as loss or degradation of certain individual miRNAs, severely compromises immune development and response, and can lead to immune disorders. Several sophisticated regulatory mechanisms are used to maintain immune homeostasis. Regulatory T (Treg) cells are essential for maintaining peripheral tolerance, preventing autoimmune diseases and limiting chronic inflammatory diseases. Recent publications have provided compelling evidence that miRNAs are highly expressed in Treg cells, that the expression of Foxp3 is controlled by miRNAs and that a range of miRNAs are involved in the regulation of immunity. A large number of studies have reported links between alterations of miRNA homeostasis and pathological conditions such as cancer, cardiovascular disease and diabetes, as well as psychiatric and neurological diseases. Although it is still unclear how miRNA controls Treg cell development and function, recent studies certainly indicate that this topic will be the subject of further research. The specific circulating miRNA species may also be useful for the diagnosis, classification, prognosis of diseases and prediction of the therapeutic response. An explosive literature has focussed on the role of miRNA. In this review, I briefly summarize the current studies about the role of miRNAs in Treg cells and in the regulation of the innate and adaptive immune response. I also review the explosive current studies about clinical application of miRNA.

Deficiency of Foxp3+ Regulatory T Cells Exacerbates Autoimmune Arthritis by Altering the Synovial Proportions of CD4+ T Cells and Dendritic Cells

BACKGROUND: CD4+Fop3+ regulatory T cells (Tregs) are needed to maintain peripheral tolerance, but their role in the development of autoimmune arthritis is still debated. The present study was undertaken to investigate the mechanism by which Tregs influence autoimmune arthritis, using a mouse model entitled K/BxN. METHODS: We generated Treg-deficient K/BxNsf mice by congenically crossing K/BxN mice with Foxp3 mutant scurfy mice. The arthritic symptoms of the mice were clinically and histopathologically examined. The proportions and activation of CD4+ T cells and/or dendritic cells were assessed in the spleens, draining lymph nodes and synovial tissue of these mice. RESULTS: K/BxNsf mice exhibited earlier onset and more aggressive progression of arthritis than their K/BxN littermates. In particular, bone destruction associated with the influx of numerous RANKL+ cells into synovia was very prominent. They also contained more memory phenotype CD4+ T cells, more Th1 and Th2 cells, and fewer Th17 cells than their control counterparts. Plasmacytoid dendritic cells expressing high levels of CD86 and CD40 were elevated in the K/BxNsf synovia. CONCLUSION: We conclude that Tregs oppose the progression of arthritis by inhibiting the development of RANKL+ cells, homeostatically proliferating CD4+ T cells, Th1, Th2 and mature plasmacytoid dendritic cells, and by inhibiting their influx into joints.

Deficiency of Foxp3+ Regulatory T Cells Exacerbates Autoimmune Arthritis by Altering the Synovial Proportions of CD4+ T Cells and Dendritic Cells

BACKGROUND: CD4+Fop3+ regulatory T cells (Tregs) are needed to maintain peripheral tolerance, but their role in the development of autoimmune arthritis is still debated. The present study was undertaken to investigate the mechanism by which Tregs influence autoimmune arthritis, using a mouse model entitled K/BxN. METHODS: We generated Treg-deficient K/BxNsf mice by congenically crossing K/BxN mice with Foxp3 mutant scurfy mice. The arthritic symptoms of the mice were clinically and histopathologically examined. The proportions and activation of CD4+ T cells and/or dendritic cells were assessed in the spleens, draining lymph nodes and synovial tissue of these mice. RESULTS: K/BxNsf mice exhibited earlier onset and more aggressive progression of arthritis than their K/BxN littermates. In particular, bone destruction associated with the influx of numerous RANKL+ cells into synovia was very prominent. They also contained more memory phenotype CD4+ T cells, more Th1 and Th2 cells, and fewer Th17 cells than their control counterparts. Plasmacytoid dendritic cells expressing high levels of CD86 and CD40 were elevated in the K/BxNsf synovia. CONCLUSION: We conclude that Tregs oppose the progression of arthritis by inhibiting the development of RANKL+ cells, homeostatically proliferating CD4+ T cells, Th1, Th2 and mature plasmacytoid dendritic cells, and by inhibiting their influx into joints.

Regulatory T Cells in the Human Immune System / 대한이비인후과학회지

Regulatory T (TReg) cells are essential for maintaining peripheral tolerance, preventing autoimmune diseases and limiting chronic inflammatory diseases. However, they also limit beneficial responses by suppressing sterilizing immunity and limiting antitumor immunity. TReg cells characterized by expression of the transcription factor Foxp3 play a key role in immune homeostasis. Rather than a monomorphic population strictly determined by Foxp3 as a 'master regulator', the emerging view is one of TReg cells as a population with many levels of complexity. Distinct subphenotypes of Foxp3+ TReg cells are found in different anatomical locations. This review will focus on these novel aspects of TReg cell diversity, and discuss recent findings regarding human TReg cells, including the ontogeny and development of TReg cell subsets that have naive or memory phenotypes, the unique mechanisms of suppression mediated by TReg cell subsets and factors that regulate TReg cell lineage commitment. We also will discuss future studies that are needed for the successful therapeutic use of human TReg cells.

Peripheral Generation of CD4+ CD25+ Foxp3+ Regulatory T Cells

CD4+ CD25+ regulatory T cells (Tregs) expressing the lineage-specific marker Foxp3 represent an important regulatory T cell that is essential for maintaining peripheral tolerance. Although it was believed that Treg development is solely dependent on the thymus, accumulating evidence demonstrates that Tregs can also be induced in the periphery. Considering the various origins of peripherally developed CD4+ CD25+ Foxp3+ regulatory T cells, it seems likely that multiple factors are involved in the peripheral generation of Tregs.

Autoimmunity / 소아과

Self/non-self discrimination and unresponsiveness to self is the fundamental properties of the immune system. Self-tolerance is a state in which the individual is incapable of developing an immune response to an individual's own antigens and it underlies the ability to remain tolerant of individual's own tissue components. Several mechanisms have been postulated to explain the tolerant state. They can be broadly classified into two groups: central tolerance and peripheral tolerance. Several mechanisms exist, some of which are shared between T cells and B cells. In central tolerance, the recognition of self-antigen by lymphocytes in bone marrow or thymus during development is required, resulting in receptor editing (revision), clonal deletion, anergy or generation of regulatory T cells. Not all self-reactive B or T cells are centrally purged from the repertoire. Additional mechanisms of peripheral tolerance are required, such as anergy, suppression, deletion or clonal ignorance. Tolerance is antigen specific. Generating and maintaining the self-tolerance for T cells and B cells are complex. Failure of self-tolerance results in immune responses against self-antigens. Such reactions are called autoimmunity and may give rise to autoimmune diseases. Development of autoimmune disease is affected by properties of the genes of the individual and the environment, both infectious and non-infectious. The host's genes affect its susceptibility to autoimmunity and the environmental factors promote the activation of self-reactive lymphocytes, developing the autoimmunity. The changes in participating antigens (epitope spreading), cells, cytokines or other inflammatory mediators contribute to the progress from initial activation to a chronic state of autoimmune diseases.

Alternation of Cytokine mRNA Expression in Human Blood Samples before and after Allogeneic Transfusions / 대한진단검사의학회지

BACKGROUND: Despite proposing clonal depletion, anergy, and alternation of cytokines in peripheral tolerance, the precise mechanism for the immunosuppressive effect of blood transfusion remains unknown. Here, we evaluated the effect of transfusion on the immune system indirectly via quantitation of leukocyte cytokine mRNA expression before and after allogeneic transfusion. METHODS: Samples were obtained from eight patients, being ordered one to four units of leukocytefree erythrocytes, before, 1, and 7 days after transfusion, from November to December, 2002 at Inha University Hospital. We explored the changes in mRNA expression of interleukin-2 (IL-2), IL-4, IL-10, tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma). RESULTS: In four patients who received blood transfusions among eight, significant changes were observed in the blood mRNA levels of INF-gamma and IL-10. The amounts of IFN-gamma mRNA were significantly decreased a day after transfusion to 78.5% and then recovered to 110.9% 7 days later (P=0.032), whereas, that of IL-10 was increased to 151.5% a day after and recovered to 119.1% 7 days later (P=0.034). mRNA expressions of IL-2, IL-4, and TNF-alpha were not detected in all patients. CONCLUSIONS: We observed a significant decrease in leukocyte IFN-gamma mRNA expression and an increase in IL-10 mRNA after transfusion. These findings indirectly represent that down-regulation of the Th1 cells and the up-regulation of the Th2 cells could be caused by allogeneic transfusion.