Regulatory T-Cells and Autoimmunity

Gene Signature of Regulatory T Cells Isolated from Children with Selective IgA Deficiency and Common Variable Immunodeficiency

Selective IgA deficiency (SIgAD) is the most common form and common variable immunodeficiency (CVID) is the most symptomatic form of predominant antibody deficiency. Despite differences in the clinical picture, a similar genetic background is suggested. A common feature of both disorders is the occurrence of autoimmune conditions. Regulatory T cells (Tregs) are the major immune cell type that maintains autoimmune tolerance. As the different types of abnormalities of Treg cells have been associated with autoimmune disorders in primary immunodeficiency (PID) patients, in our study we aimed to analyze the gene expression profiles of Treg cells in CVID and SIgAD patients compared to age-matched healthy controls. The transcriptome-wide gene profiling was performed by microarray technology. As a result, we analyzed and visualized gene expression patterns of isolated population of Treg cells. We showed the differences at the gene level between patients with and without autoimmunizations. Our findings suggest that the gene signatures of Treg cells isolated from SIgAD and CVID patients differ from age-matched healthy controls and from each other, presenting transcriptional profiles enriched in innate immune or Th response, respectively. The occurrence of autoimmunity in both types of PID is associated with down-regulation of class I IFNs signaling pathways. In summary, our findings improve our understanding of Treg dysfunctions in patients with common PIDs and associated autoimmunity.

Transcriptome profiling of regulatory T cells from children with transient hypogammaglobulinemia of infancy

Transient hypogammaglobulinemia of infancy (THI) is one of the most common forms of hypogammaglobulinemia in the early childhood. THI is usually associated with chronic, recurrent bacterial and viral infections, life-threatening in some cases, yet its pathogenesis is still largely unknown. As our previous findings indicated the possible role of Treg cells in the pathomechanism of THI, the aim of the current study was to investigate gene expression profile of Treg cells isolated from THI patients. The transcriptome-wide gene profiling was performed using microarray technology on THI patients in two time-points: during (THI-1), and in resolution phase (THI-2) of hypogammaglobulinemia. As a result, a total of 1086 genes were differentially expressed in THI-1 patients, when compared to THI-2 as well as control group. Among them, 931 were up- and 155 downregulated, and part of them encodes genes important for Treg lymphocyte biology and function, i.e. transcription factors/cofactors that regulate FOXP3 expression. Thus, we postulate that Treg cells isolated from THI patients during hypogammaglobulinemia display enhanced suppressor transcriptome signature. Treg expression profile of THI children after normalization of Ig levels largely resembles the results obtained in healthy control group, suggesting THI Treg transcriptome seems to return to that observed in healthy children. Taken together, we suggest that THI pathomechanism is associated not only with transiently elevated Treg cell numbers, but also with their enhanced regulatory/inhibitory functions. These findings expand our knowledge of human Treg cells and may be useful for the future diagnosis or management of THI.

Ras family signaling pathway in immunopathogenesis of inflammatory rheumatic diseases

The Ras (rat sarcoma virus) is a GTP-binding protein that is considered one of the important members of the Ras-GTPase superfamily. The Ras involves several pathways in the cell that include proliferation, migration, survival, differentiation, and fibrosis. Abnormalities in the expression level and activation of the Ras family signaling pathway and its downstream kinases such as Raf/MEK/ERK1-2 contribute to the pathogenic mechanisms of rheumatic diseases including immune system dysregulation, inflammation, and fibrosis in systemic sclerosis (SSc); destruction and inflammation of synovial tissue in rheumatoid arthritis (RA); and autoantibody production and immune complexes formation in systemic lupus erythematosus (SLE); and enhance osteoblast differentiation and ossification during skeletal formation in ankylosing spondylitis (AS). In this review, the basic biology, signaling of Ras, and abnormalities in this pathway in rheumatic diseases including SSc, RA, AS, and SLE will be discussed.

The role of regulatory T cells, interleukin-10 and in vivo scintigraphy in autoimmune and idiopathic diseases - Therapeutic perspectives and prognosis

Previous studies have demonstrated the expression of the CD25 marker on the surface of naturally occurring T cells (Tregs) of mice, which have a self-reactive cellular profile. Recently, expression of other markers that aid in the identification of these cells has been detected in lymphocyte subtypes of individuals suffering of autoimmune and idiopathic diseases, including: CD25, CTLA-4 (cytotoxic T-lymphocyte antigen 4), HLA-DR (human leukocyte antigen) and Interleukin 10 (IL-10), opening new perspectives for a better understanding of an association between such receptors present on the cell surface and the prognosis of autoimmune diseases. The role of these molecules has already been described in the literature for the modulation of the inflammatory response in infectious and parasitic diseases. Thus, the function, phenotype and frequency of expression of the a-chain receptor of IL-2 (CD25) and IL-10 in lymphocyte subtypes were investigated. Murine models have been used to demonstrate a possible correlation between the expression of the CD25 marker (on the surface of CD4 lymphocytes) and the control of self-tolerance mechanisms. These studies provided support for the presentation of a review of the role of cells expressing IL-2, IL-10, HLA-DR and CTLA-4 receptors in the monitoring of immunosuppression in diseases classified as autoimmune, providing perspectives for understanding peripheral regulation mechanisms and the pathophysiology of these diseases in humans. In addition, a therapeutic approach based on the manipulation of the phenotype of these cells and ways of scintigraphically monitoring the manifestations of these diseases by labeling their receptors is discussed as a perspective. In this paper, we have included the description of experiments in ex vivo regulation of IL-10 and synthesis of thio-sugars and poly-sugars to produce radiopharmaceuticals for monitoring inflammation. These experiments may yield benefits for the treatment and prognosis of autoimmune diseases.

The Yin and Yang of regulatory T cell and therapy progress in autoimmune disease

Autoimmune diseases (ADs) are primarily mediated by the failure of immunological self-tolerance. Regulatory T cells (Tregs) play a critical role in the maintenance of induced tolerance to peripheral self-antigens, suppressing immoderate immune responses deleterious to the host and preventing the AD development. Tregs and suppressive cytokines are homeostatic with effective cells plus pro-inflammatory cytokines in healthy hosts which is defined as "Yang", and ADs are usually induced in case of disturbed homeostasis, which is defined as "Yin". Indeed, the Yin-Yang balance could explain the pathogenic mechanism of ADs. Tregs not only suppress CD4⁺ and CD8⁺ T cells but also can suppress other immune cells such as B cell, natural killer cell, DC and other antigen-presenting cell through cell-cell contact or secreting suppressive cytokines. In Tregs, Foxp3 as an intracellular protein displays a more specific marker than currently used other cell-surface markers (such as CD25, CD40L, CTLA-4, ICOS and GITR) in defining the naturally occurring CD4⁺ Tregs. Though the precise mechanism for the opposite effects of Tregs has not been fully elucidated, the importance of Tregs in ADs has been proved to be associated with kinds of immunocytes. At present, the surface marker, frequency and function of Tregs existed conflicts and hence the Tregs therapy in ADs faces challenges. Though some success has been achieved with Tregs therapy in few ADs both in murine models and humans, more effort should paid to meet the future challenges. This review summarizes the progress and discusses the phenotypic, numeric and functional abnormalities of Tregs and is the first time to systematically review the progress of Tregs therapy in kinds of ADs.

Astragalus polysaccharides attenuate postburn sepsis via inhibiting negative immunoregulation of CD4+ CD25(high) T cells

BACKGROUND

Astragalus polysaccharides (APS) isolated from one of the Chinese herbs, Astragalus mongholicus, are known to have a variety of immunomodulatory activities. However, it is not yet clear whether APS can exert an effect on the immune functions of regulatory T cells (Tregs). This study was carried out to investigate the effect of APS on the immune function of peripheral blood Tregs in postburn sepsis.

METHODOLOGY/PRINCIPAL FINDINGS

BALB/C mice were randomly divided into six groups as follows: sham burn group, burn control (burn without infection animals) group, burn plus P. aeruginosa group, burn plus P. aeruginosa with APS (50 mg/kg) treatment group, burn plus P. aeruginosa with APS (100 mg/kg) treatment group, and burn plus P. aeruginosa with APS (200 mg/kg) treatment group, and they were sacrificed on postburn day 1, 3, 5, and 7, respectively, with seven animals at each time point. Magnetic microbeads were used to isolate peripheral blood Tregs and CD4(+) T cells. Phenotypes were analyzed by flow cytometry, and cytokine levels were determined with ELISA. In the burn plus P. aeruginosa group, forkhead/winged helix transcription factor p3 (Foxp3) expression on CD4(+)CD25(+)Tregs were strongly enhanced in comparison to the sham group, and the capacity of CD4(+)CD25(+)Tregs to produce interleukin (IL)-10 was markedly increased. Administration of APS to inhibit CD4(+)CD25(+)Tregs could significantly decrease expression of Foxp3 on CD4(+)CD25(+)Tregs, and IL-10 production in burned mice with P. aeruginosa infection. At the same time, proliferative activity and expression of IL-2 and IL-2Rα on CD4(+) T cells were restored. In contrast, anti-Toll-like receptor 4 (TLR4) antibody could block the effect of APS on Tregs immune function.

CONCLUSION

APS might suppress CD4(+)CD25(+)Treg activity, at least in part, via binding TLR4 on Tregs and trigger a shift of Th2 to Th1 with activation of CD4(+) T cells in burned mice with P. aeruginosa infection.

Astragalus polysaccharides attenuate postburn sepsis via inhibiting negative immunoregulation of CD4+ CD25(high) T cells

Backgroud

Astragalus polysaccharides (APS) isolated from one of the Chinese herbs, Astragalus mongholicus, are known to have a variety of immunomodulatory activities. However, it is not yet clear whether APS can exert an effect on the immune functions of regulatory T cells (Tregs). This study was carried out to investigate the effect of APS on the immune function of peripheral blood Tregs in postburn sepsis.

Methodology/Principal Findings

BalB/c mice were randomly divided into six groups as follows: sham burn group, burn control(burn without infection animals) group, burn plus P. aeruginosa group, burn plus P. aeruginosa with APS (50 mg/kg) treatment group, burn plus P. aeruginosa with APS (100 mg/kg) treatment group, and burn plus P. aeruginosa with APS (200 mg/kg) treatment group, and they were sacrificed on postburn day 1, 3, 5, and 7, respectively, with seven animals at each time point. Magnetic microbeads were used to isolate peripheral blood Tregs and CD4⁺ T cells. Phenotypes were analyzed by flow cytometry, and cytokine levels were determined with ELISA. In the burn plus P. aeruginosa group, forkhead/winged helix transcription factor p3 (Foxp3) expression on CD4⁺CD25⁺Tregs were strongly enhanced in comparison to the sham group, and the capacity of CD4⁺CD25⁺Tregs to produce interleukin (IL)-10 was markedly increased. Administration of APS to inhibit CD4⁺CD25⁺Tregs could significantly decrease expression of Foxp3 on CD4⁺CD25⁺Tregs, and IL-10 production in burned mice with P. aeruginosa infection. At the same time, proliferative activity and expression of IL-2 and IL-2Rα on CD4⁺ T cells were restored. In contrast, anti-Toll-like receptor 4 (TLR4) antibody could block the effect of APS on Tregs immune function.

Conclusion

APS might suppress CD4⁺CD25⁺Treg activity, at least in part, via binding TLR4 on Tregs and trigger a shift of Th2 to Th1 with activation of CD4⁺ T cells in burned mice with P. aeruginosa infection.

The New Zealand black mouse as a model for the development and progression of chronic lymphocytic leukemia

BACKGROUND

Similar to a subset of human patients who progress from monoclonal B lymphocytosis (MBL) to chronic lymphocytic leukemia (CLL), New Zealand Black (NZB) mice have an age-associated progression to CLL. The murine disease is linked to a genetic abnormality in microRNA mir-15a/16-1 locus, resulting in decreased mature miR-15a/16.

METHODS

Spleens of aging NZB were analyzed for the presence of B-1 cells via flow cytometry and for the presence of a side population (SP) via the ability of cells to exclude Hoechst 33342 dye. The SP was assayed for the presence of hyperdiploid B-1 clones and for the ability to differentiate into B-1 cells in vitro and transfer disease in vivo. In addition, enhanced apoptosis of chemoresistant NZB B-1 cells was examined by restoring miR-16 levels in nutlin-treated cells.

RESULTS

Aging NZB mice develop a B-1 expansion and clonal development that evolves from MBL into CLL. An expansion in SP is also seen. Although the SP did contain increased cells with stem cell markers, they lacked malignant B-1 cells and did not transfer disease in vivo. Similar to B-1 cells, splenic NZB SP also has decreased miR-15a/16 when compared with C57Bl/6. Exogenous addition of miR-15a/16 to NZB B-1 cells resulted in increased sensitivity to nutlin.

CONCLUSION

NZB serve as an excellent model for studying the development and progression of age-associated CLL. NZB SP cells do not seem to contain cancer stem cells, but rather the B-1 stem cell. NZB B-1 chemoresistance may be related to reduced miR-15a/16 expression.

Autoimmune type I diabetes mellitus in a perinatally HIV infected patient with a well-preserved immune system

We report an 8 year-old girl with well-controlled perinatally acquired HIV infection who developed autoimmune type 1 diabetes mellitus (DM1A) confirmed by the presence of diabetes-related auto-antibodies. Although non-autoimmune insulin dependent diabetes mellitus (DM1B) and more frequently type 2 DM has been reported in patients affected with HIV, this is the first report of DM1A diagnosed in an HIV positive patient.

Quantification and molecular characterization of regulatory T cells in connective tissue diseases

The aim of our study was to investigate and characterize regulatory T cells (Treg) in peripheral blood of patients with connective tissue diseases (Systemic lupus erythematosus, systemic sclerosis, Sjögren's syndrome, poly- and dermatomyositis) as compared with blood from healthy controls. Treg cells were quantified and phenotypically characterized by flow cytometry while the expression level of Foxp3 mRNA was evaluated by real time PCR. A reduced percentage of peripheral blood Treg cells was found in patients than in controls, irrespective of the type of connective tissue disease. Treg cells, especially those expressing one of the phenotypical markers, seemed to differ not only between patients and healthy controls but also among types of diseases. Additionally, the presence of autoantibodies as well as disease activity appeared to be correlated with particular Treg cell populations, especially those expressing one of the examined phenotypical markers. Correlations with therapy suggested that glucocorticoids plus antimalarial or other immunosuppressor drugs diminished the percentage of Treg cells, especially of those with memory phenotype. These findings indicated dysregulations at the level of Treg cells and suggested an involvement of these cells in the pathology of connective tissue diseases. Moreover, our data are in agreement with the suggestion that Treg cells could be therapeutic targets for some autoimmune diseases.

A TLR2 polymorphism is associated with type 1 diabetes and allergic asthma

Type 1 diabetes (T1D) and allergic asthma are immune-mediated diseases. Pattern recognition receptors are proteins expressed by cells in the immune system to identify microbial pathogens and endogenous ligands. Toll-like receptors (TLRs) and CD14 are members of this family and could represent a molecular link between microbial infections and immune-mediated diseases. Diverging hypotheses regarding whether there exists a common or inverse genetic etiology behind these immune-mediated diseases have been presented. We aimed to test whether there exist common or inverse associations between polymorphisms in the pattern recognition receptors TLR2, TLR4 and CD14 and T1D and allergic asthma. Eighteen single nucleotide polymorphisms (SNPs) were genotyped in TLR2 (2), TLR4 (12) and CD14 (4) in 700 T1D children, 357 nuclear families with T1D children and 796 children from the 'Environment and Childhood Asthma' study. Allele and haplotype frequencies were analyzed in relation to diseases and in addition transmission disequilibrium test analyses were performed in the family material. Both T1D and allergic asthma were significantly associated with the TLR2 rs3804100 T allele and further associated with the haplotype including this SNP, possibly representing a susceptibility locus common for the two diseases. Neither TLR4 nor CD14 were associated with T1D or allergic asthma.

Regulatory T cells as central regulators of both autoimmunity and B cell malignancy in New Zealand Black mice

Regulatory T cells (Tregs) play an important role in protection against autoimmune disease and are also known to be potent inhibitors of anti-tumor immune responses. The New Zealand Black (NZB) mouse is a murine model for both autoimmune diseases, since high levels of autoantibodies are present, and human CLL, due to the expansion of malignant B-1 cells. In this study, we examined the functional role of CD4(+)CD25(+) Foxp3(+) Tregs in these different manifestations. Flow cytometric analysis showed increased levels of Tregs in NZB mice compared to healthy C57Bl/6 controls. Aged NZB mice that have developed a B-1 cell malignancy identified as IgM(+)CD5(+), have the most pronounced increase in Tregs. Ex vivo treatment of splenocytes from NZB mice with IFN-alpha resulted in a decrease in the frequency of Tregs and malignant B-1 cells. In vivo treatment of both NZB and C57Bl/6 mice with poly (I:C), a potent inducer of IFN-alpha, also led to a decrease in the levels of Tregs and malignant B-1 cells (NZB only) while amplifying autoimmune manifestations. These results indicate that while high levels of Tregs found in NZB mice might suppress a more severe autoimmune disease, they may also contribute to the development of the B cell malignancy.

Dietary gluten reduces the number of intestinal regulatory T cells in mice

It is well established that gluten-free diet reduces the incidence of type 1 diabetes mellitus (T1D) in non-obese diabetic (NOD) mice, though the mechanism is not known. However, regulatory T cells (Treg) are likely to play an important role. Also, it is known that dietary gluten induces an intestinal increase in the bacterium Lactococcus garvieae, but the importance of this phenomenon for T1D development is doubtful. Our hypothesis is that gluten is responsible for mediating its effect on T1D through the influence on Treg development independent of gluten-induced Lactococci. Four groups of female NOD and BALB/c mice of 3 week old were fed either a gluten-free diet or a standard diet. Lactococcus garvieae or saline water was administered per oral to one of each dietary group. Spleen and Peyer's patches were sampled from BALB/c mice for flow cytometric monitoring of IL-10 and Treg. NOD mice were diagnosed diabetic with blood glucose level >12 mmol/l. Dietary gluten significantly decreased the occurrence of Tregs by 10-15% (P < 0.05) in mice compared with those fed a standard diet. These results and the diabetes incidence were independent of the gluten-induced bacterial factor Lactococci. The prevalence of Treg was 5- to 10-fold more abundant in the Peyer's patches than in the spleen (P < 0.001). In conclusion, dietary gluten has a significant negative quantitative impact on the generation of Treg in mice, independent of gluten-induced Lactococcus garvieae, and Treg are far more abundant in Peyer's patches than in the spleen.

The autoimmune origin of atherosclerosis

Atherosclerosis is a chronic inflammatory disease. Many studies and observations suggest that it could be caused by an immune reaction against autoantigens at the endothelial level, the most relevant of which are oxidized LDL and heat shock proteins (HSP) 60/65. Endothelial dysfunction plays a fundamental role. The first antigen is related to the increased leakage and oxidation of LDL; the second to cellular reaction to stress. Experimental and clinical observations confirm the pathogenetic role of these antigens. Both innate and adaptive immunity and impaired regulatory mechanisms of the autoimmune reaction are involved. Different triggering factors are examined: infectious agents, smoking, air pollution, diabetes and hypercholesterolemia. Analogies and differences between systemic atherosclerosis and transplant-related coronary atherosclerosis help to understand their respective nature. Immune mechanisms might be responsible for the passage from stable plaque to unstable and rupture-prone plaque. Finally, prospects of treatment and prevention are linked to the induction of tolerance to responsible antigens, activation of immune regulatory response and the use of immunomodulatory drugs.

The role of Ras signaling in lupus T lymphocytes: biology and pathogenesis

Ras is a GTP-binding protein that plays multiple important roles in cell activation, including proliferative and inflammatory responses. Ras regulation is complex and depends upon post-translational processing, organelle-specific localization and the activation/deactivation of Ras by a number of regulatory molecules. Ras activation in T lymphocytes demonstrates unique features, including its dependence on the T cell receptor and the ability of Ras to signal from both the plasma membrane and the Golgi. Abnormalities of Ras expression, activation and signaling pathways in T lymphocytes appear to play important roles in the development of autoimmunity in general, and systemic lupus erythematosus in particular. In this manuscript, we review the basic biology of Ras in T lymphocytes, and the ways in which T lymphocyte Ras abnormalities may contribute to the development of a lupus phenotype.

Functional compartmentalization following induction of long-term graft survival with pregraft donor-specific transfusion

Long-term survival is achieved in rat recipients by pre-graft donor-specific blood transfusion. We characterized the immune compartments in long-term survivors and analyzed them for capacity to transfer tolerance and protect against chronic rejection. Splenocytes and spleen T cells from treated recipients transferred long-term graft survival to 100% of secondary recipients. In contrast, blood transferred graft survival to only 50% of recipients whereas blood T cells had no effect. An unaltered TCR repertoire, an increase in suppressive CD4+CD25+ T cells, a decrease in antidonor T-cell proliferative response and normal perforin-granzyme levels were the hallmarks of the spleen T cells. Blood T cells were characterized by a strongly altered CD8+ repertoire, normal CD4+CD25+ T cell number with unchanged antidonor T-cell proliferative response, an activated T-cell phenotype and an increase in perforin-granzyme levels. However, following the transfer of blood or spleen cells into secondary recipients, all grafts displayed chronic rejection. These findings provide evidence that distinct compartments play critical roles in DST recipients. Regulatory cells do not accumulate in blood, which appears to be a reservoir for cytotoxic T cells. Spleen T cells, which display a regulatory-like profile and transfer graft survival, are not able to prevent chronic rejection.

Immune regulation of T lymphocyte by a newly characterized human umbilical cord blood stem cell

Previous work identified a novel type of stem cell from human umbilical cord blood, designated cord blood-stem cells (CB-SC). To further evaluate their immune characteristics, we cocultured CB-SC with allogeneic peripheral blood lymphocytes in the presence of phytohaemagglutinin (PHA) or interleukin-2 (IL-2). Results showed that CB-SC could significantly inhibit lymphocyte proliferation and reduce tyrosine phosphorylation of STAT5 in both PHA- and IL-2-stimulated lymphocytes, along with the regulation on the phenotypes of CD4+ and CD8+ T cells. Additionally, CB-SC also suppressed the proliferation of IL-2-stimulated CD4+CD25+ regulatory T cells. Mechanism studies revealed that programmed death receptor-1 ligand 1 (PD-L1) expressed on CB-SC membrane, together with a soluble factor nitric oxide (NO) released by PHA-stimulated CB-SC, not prostaglandin E2 (PGE2) and transforming growth factor-beta1 (TGF-beta1), mainly contributed to the T cell suppression induced by CB-SC, as demonstrated by blocking experiments with a nitric oxide synthase inhibitor (Nomega-nitro-l-arginine, l-NNA) and a neutralizing antibody to PD-L1. Our findings may advance our understanding of the immunobiology of stem cells and facilitate the therapeutic application of cord blood stem cells.