B cell-deficient NOD.H-2h4 mice have CD4+CD25+ T regulatory cells that inhibit the development of spontaneous autoimmune thyroiditis

Phenotypic Landscape of Immune Cells in Sepsis: Insights from High-Dimensional Mass Cytometry

Understanding the sepsis-induced immunological response can be facilitated by identifying phenotypic changes in immune cells at the single-cell level. Mass cytometry, a novel multiparametric single-cell analysis technique, offers considerable benefits in characterizing sepsis-induced phenotypic changes in peripheral blood mononuclear cells. Here, we analyzed peripheral blood mononuclear cells from 20 sepsis patients and 10 healthy donors using mass cytometry and employing 23 markers. Both manual gating and automated clustering approaches (PhenoGraph) were used for cell identification, complemented by uniform manifold approximation and projection (UMAP) for dimensionality reduction and visualization. Our study revealed that patients with sepsis exhibited a unique immune cell profile, marked by an increased presence of monocytes, B cells, and dendritic cells, alongside a reduction in natural killer (NK) cells and CD4/CD8 T cells. Notably, significant changes in the distributions of monocytes and B and CD4 T cells were observed. Clustering with PhenoGraph unveiled the subsets of each cell type and identified elevated CCR6 expression in sepsis patients' monocyte subset (PG#5), while further PhenoGraph clustering on manually gated T and B cells discovered sepsis-specific CD4 T cell subsets (CCR4low CD20low CD38low) and B cell subsets (HLA-DRlow CCR7low CCR6high), which could potentially serve as novel diagnostic markers for sepsis.

A systematic review of dysregulated microRNAs in Hashimoto's thyroiditis

BACKGROUND

Plenty of evidence suggests that dysregulated microRNAs are linked to developing autoimmune thyroid diseases. In this study, we aimed to identify commonly linked dysregulated microRNAs in Hashimoto's thyroiditis(HT) and explore microRNA-targeted genes and the involved pathways.

METHODS

Embase, PubMed, Web of Science, and Scopus databases were searched using the MeSH terms and free text terms, which yielded 11879 articles published up to July 2023. Two-step screening(first for titles and second for abstracts) was completed according to inclusion and exclusion criteria. The search strategy was formulated using the PEO format(Population, Exposure, and Outcome) for observational studies. The corresponding target genes and relevant signaling pathways were also identified using web servers of Diana Tools/its mirPath v.3 software, miRNA Enrichment Analysis, Mirpath DB2, miRPathDB 2.0, and miRmap.

RESULTS

Review inclusion criteria were met by 16 studies. Thirty-three microRNAs were identified as differentially expressed in HT patients compared to a healthy control after qRT-PCR or RNA sequencing confirmation. Only three miR-146a, miR-142, and miR-301 showed significant results in more than two studies comparing HT cases with healthy controls.

CONCLUSION

Three key microRNAs in HT were identified by systematic review; the corresponding target genes and signaling pathways involved in the target genes were also identified. These microRNAs regulate the immune response and inflammation and may favor the development and progression of HT. These data may be beneficial to make a step forward to understand the exact etiology of HT and use of these MicroRNAs as possible diagnostic and prognostic biomarkers and as target therapy.

Peripheral immunophenotyping of AITD subjects reveals alterations in immune cells in pediatric vs adult-onset AITD

Autoimmune thyroid disease (AITD) is caused by aberrant activation of the immune system allowing autoreactive B and T cells to target the thyroid gland leading to disease. Although AITD is more frequently diagnosed in adults, children are also affected but rarely studied. Here, we performed phenotypic and functional characterization of peripheral blood immune cells from pediatric and adult-onset AITD patients and age-matched controls using mass cytometry. Major findings indicate that unlike adult-onset AITD patients, pediatric AITD patients exhibit a decrease in anergic B cells (B_ND) and DN2 B cells and an increase in immature B cells compared to age-matched controls. These results indicate alterations in peripheral blood immune cells seen in pediatric-onset AITD could lead to rapid progression of disease. Hence, this study demonstrates diversity of AITD by showing differences in immune cell phenotypes and function based on age of onset, and may inform future therapies.

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Penetrance of high-risk HLA-DR3 haplotype is higher in pediatric AITD patients

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Pediatric AITD patients display altered frequency of autoreactive B cell subsets

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Immune cell subset frequency and function is similar in adult AITD and controls

Disappearance of Anti-Thyroid Autoantibodies following Thymectomy in Patients with Myasthenia Gravis

OBJECTIVES

The thymus plays a central role in immune tolerance, which prevents autoimmunity. Myasthenia gravis (MG) is commonly associated with thymoma or thymus hyperplasia, and it can coexist with autoimmune thyroid diseases. However, the role of the thymus in thyroid autoimmunity remains to be clarified, which we investigated here.

STUDY DESIGN

The study design entailed the inclusion of consecutive MG patients and the measurement of anti-thyroid autoantibodies at baseline and, limited to autoantibody-positive patients, also at 24 and 48 weeks. One hundred and seven MG patients were studied. The main outcome measure was the behaviour of anti-thyroglobulin autoantibodies (TgAbs) and anti-thyroperoxidase autoantibodies (TPOAbs) over time in relation to thymectomy.

RESULTS

Serum TgAbs and/or TPOAbs were detected in ∼20% of patients in the absence of thyroid dysfunction. The prevalence of positive serum TgAbs and/or TPOAbs decreased significantly (p = 0.002) over the follow-up period in patients who underwent thymectomy, but not in patients who were not thymectomized. When the analysis was restricted to TgAbs or TPOAbs, findings were similar. On the same line, there was a general trend towards a reduction in the serum concentrations of anti-thyroid autoantibodies in patients who underwent thymectomy, which was significant for TPOAbs (p = 0.009).

CONCLUSIONS

Our findings suggest a role of the thymus in the maintenance of humoral thyroid autoimmunity.

Reversal of Abnormal CD4+ T Cell Metabolism Alleviates Thyroiditis by Deactivating the mTOR/HIF1a/Glycolysis Pathway

BACKGROUND

Hashimoto's thyroiditis (HT) is an autoimmune disease that features activation of thyroid antigen-specific helper T cells. HT patients have increased Th1 and Th17 T cell subsets. Glycolysis supports chronic activation of Th1 and Th17 T cells, but how this contributes to HT remains unknown.

METHODS

The metabolism of CD4+ T cells from 30 HT patients and 30 healthy controls was evaluated by determining the extracellular acidification rate (ECAR) and the oxygen consumption rate (OCR). Mice in a subacute thyroiditis (SAT) model were treated with 2DG, metformin, or combination. Metrics of mTOR/HIF-1α/HK2/glycolysis were measured by western blot and Seahorse assay methods. The severity of SAT was measured by flow cytometry and HE staining.

RESULTS

CD4+ T cells from HT patients had enhanced ECAR and OCR. Levels of Glut1, HK2, PKM2, and LDHA in cultured HT CD4+ T cells were elevated. The expression of HK2 and PKM2 in cultured SAT CD4+ T cells was elevated compared with the control group. Activation of the mTOR and HIF-1α pathways was significant in SAT mice, and expression of HIF-1α in the 2DG treated group was reduced. Treatment with 2DG and/or metformin significantly decreased the ratio of Th17 and Th1 T cells.

CONCLUSIONS

Thyroiditis results in elevation of the mTOR/HIF-1α/HK2/glycolysis pathway in CD4+ T cells. The activation of this pathway is reduced by treatment with 2DG and metformin, which also reverted imbalances in CD4+ T cell differentiation.

Increased circulating Tfh17 and PD-1+Tfh cells are associated with autoantibodies in Hashimoto's thyroiditis

OBJECTIVE

Hashimoto's thyroiditis (HT) is characterized by autoantibodies targeting the thyroid. Abnormal CD4⁺CXCR5⁺T cell levels were previously shown to be associated with HT. However, Tfh cells consist of heterogeneous subpopulations, and which T follicular helper (Tfh) cell subpopulation participates in the pathogenesis of HT remains poorly understood.

METHODS

Thirty healthy controls (HCs) and 52 HT patients were enrolled in the study. The percentages of Tfh, ICOS⁺Tfh, PD1⁺Tfh, Tfh1, Tfh2, Tfh17, effector Tfh, resting Tfh, effector memory Tfh, central memory Tfh, and naïve Tfh cells in the peripheral blood were all determined via flow cytometry, and the associations between the percentages of these cells and thyroid function indices were also investigated.

RESULTS

The percentage of Tfh cells was significantly higher in HT patients than in HCs. Examination of the Tfh cell subsets revealed that the percentages of Tfh1, Tfh2, and resting Tfh cells were significantly decreased, while those of the ICOS⁺Tfh, PD1⁺Tfh, Tfh17, and effector Tfh cells were significantly increased in HT patients. No significant differences in effector memory, central memory or naïve Tfh cell percentages were noted between the HC and HT groups. Furthermore, the percentage of PD1⁺Tfh cells was positively correlated with anti-thyroglobulin antibody levels. Most importantly, only Tfh17 cell percentages were positively correlated with anti-thyroglobulin and anti-thyroid peroxidase antibody levels and were negatively correlated serum free T3 and free T4 levels in HT patients.

CONCLUSIONS

Increased circulating Tfh17 cell and PD1⁺Tfh percentages are associated with higher autoantibody levels in HT patients, which imply that Tfh17 or PD1⁺Tfh cells may play a pathogenic role in the development of HT.

Alterations of the Gut Microbiota in Hashimoto's Thyroiditis Patients

BACKGROUND

Hashimoto's thyroiditis (HT) is an organ-specific autoimmune disease in which both genetic predisposition and environmental factors serve as disease triggers. Many studies have indicated that alterations in the gut microbiota are important environmental factors in the development of inflammatory and autoimmune diseases. A comparative analysis was systematically performed of the gut microbiota in HT patients and healthy controls.

METHODS

First, a cross-sectional study of 28 HT patients and 16 matched healthy controls was conducted. Fecal samples were collected, and microbiota were analyzed using 16S ribosomal RNA gene sequencing. Second, an independent cohort of 22 HT patients and 11 healthy controls was used to evaluate the diagnostic potential of the selected biomarkers.

RESULTS

Similar levels of bacterial richness and diversity were found in the gut microbiota of HT patients and healthy controls (p = 0.11). A detailed fecal microbiota Mann-Whitney U-test (Q value <0.05) revealed that the abundance levels of Blautia, Roseburia, Ruminococcus_torques_group, Romboutsia, Dorea, Fusicatenibacter, and Eubacterium_hallii_group genera were increased in HT patients, whereas the abundance levels of Fecalibacterium, Bacteroides, Prevotella_9, and Lachnoclostridium genera were decreased. A correlation matrix based on the Spearman correlation distance confirmed correlations among seven clinical parameters. Additionally, the linear discriminant analysis effect size method showed significant differences in 27 genera between the two groups that were strongly correlated with clinical parameters. The linear discriminant analysis value was used to select the first 10 species from the 27 different genera as biomarkers, achieving area under the curve values of 0.91 and 0.88 for exploration and validation data, respectively.

CONCLUSIONS

Characterization of the gut microbiota in HT patients confirmed that HT patients have altered gut microbiota and that gut microbiota are correlated with clinical parameters, suggesting that microbiome composition data could be used for disease diagnosis. Further investigation is required to understand better the role of the gut microbiota in the pathogenesis of HT.

Activation of thyroid antigen-reactive B cells in recent onset autoimmune thyroid disease patients

Autoimmune thyroid disease (AITD), including Hashimoto's thyroiditis (HT) and Graves' disease (GD), is the most common autoimmune disorder in the United States, affecting over 20 million people. At the time of diagnosis, both HD and GD are characterized by the accumulation of B and T lymphocytes in the thyroid gland and production of autoantibodies targeting the thyroid, indicating that a breach in tolerance of autoreactive lymphocytes has occurred. However, few studies have sought to understand the underlying pathogenesis of AITD that ultimately leads to production of autoantibodies and loss of thyroid function. In this study, we analyzed the phenotype of thyroid antigen-reactive B cells in the peripheral blood of recent onset and long standing AITD patients. We found that in recent onset patients thyroid antigen-reactive B cells in blood no longer appear anergic, rather they express CD86, a marker of activation. This likely reflects activation of these cells leading to their production of autoantibodies. Hence, this study reports the early loss of anergy in thyroid antigen-reactive B cells, an event that contributes to development of AITD.

CD19+CD24hiCD38hi regulatory B cells are associated with insulin resistance in type I Hashimoto's thyroiditis in Chinese females

Hashimoto's thyroiditis (HT) is typically associated with insulin resistance. The aim of the present study was to investigate the role of regulatory B cells (Bregs) in insulin resistance in patients with HT. A total of 52 female patients with type I HT and 35 matched healthy volunteers were enrolled. Demographic and laboratorial data were collected. A 75 g oral glucose tolerance test was performed on each subject. Flow cytometry was performed to evaluate the levels of CD19⁺CD24^hiCD38^hi Bregs in peripheral blood. Patients with HT exhibited significantly higher postprandial insulin levels (P<0.01), but normal glucose levels. The level of CD19⁺CD24^hiCD38^hi Bregs in patients with HT decreased significantly (P=0.0002) compared with the controls. Pearson's linear correlation model revealed a significant, negative association between anti-thyroid peroxidase antibodies (TPOAb) and homeostasis model assessment of β cell (r=-0.313, P=0.014). The same correlation model revealed a significant, negative association between TPOAb and the disposition index (DI; r=-0.305, P=0.017), and between anti-thyroglobulin antibodies and DI (r=-0.321, P=0.013). Patients with a decreased ratio of CD19⁺CD24^hiCD38^hi Bregs to CD19⁺ lymphocytes exhibited higher levels of total cholesterol and low-density lipoprotein cholesterol. A decrease in the ratio of CD19⁺CD24^hiCD38^hi Bregs to lymphocytes was a significant independent risk factor for hyperinsulinemia (odds ratio=1.372, P=0.035). A decrease in peripheral blood CD19⁺CD24^hiCD38^hi Bregs is associated with insulin resistance in HT patients, and was an independent risk factor for postprandial hyperinsulinemia. The present study provided a novel insight into the development of effective therapeutic strategies targeting immune mechanisms associated with HT.

The RNA-binding protein HuR contributes to neuroinflammation by promoting C-C chemokine receptor 6 (CCR6) expression on Th17 cells

In both multiple sclerosis and experimental autoimmune encephalomyelitis (EAE), the C-C chemokine receptor 6 (CCR6) is critical for pathogenic T helper 17 (Th17) cell migration to the central nervous system (CNS). Whereas many cytokines and their receptors are potently regulated via post-transcriptional mechanisms in response to various stimuli, how CCR6 expression is post-transcriptionally regulated in Th17 cells is unknown. Here, using RNA-binding protein HuR conditional knock-out (KO) and wild-type (WT) mice, we present evidence that HuR post-transcriptionally regulates CCR6 expression by binding to and stabilizing Ccr6 mRNA and by promoting CCR6 translation. We also found that HuR down-regulates several microRNA expressions, which could target the 3'-UTR of Ccr6 mRNA for decay. Accordingly, knock-out of HuR reduced CCR6 expression on Th17 cells and impaired their migration to CNS compared with the response of WT Th17 cells and thereby ameliorated EAE. Together, these findings highlight how HuR contributes to Th17 cell-mediated autoimmune neuroinflammation and support the notion that targeting HuR might be a potential therapeutic intervention for managing autoimmune disorders of the CNS.

Mechanisms by Which B Cells and Regulatory T Cells Influence Development of Murine Organ-Specific Autoimmune Diseases

Experiments with B cell-deficient (B−/−) mice indicate that a number of autoimmune diseases require B cells in addition to T cells for their development. Using B−/− Non-obese diabetic (NOD) and NOD.H-2h4 mice, we demonstrated that development of spontaneous autoimmune thyroiditis (SAT), Sjogren’s syndrome and diabetes do not develop in B−/− mice, whereas all three diseases develop in B cell-positive wild-type (WT) mice. B cells are required early in life, since reconstitution of adult mice with B cells or autoantibodies did not restore their ability to develop disease. B cells function as important antigen presenting cells (APC) to initiate activation of autoreactive CD4+ effector T cells. If B cells are absent or greatly reduced in number, other APC will present the antigen, such that Treg are preferentially activated and effector T cells are not activated. In these situations, B−/− or B cell-depleted mice develop the autoimmune disease when T regulatory cells (Treg) are transiently depleted. This review focuses on how B cells influence Treg activation and function, and briefly considers factors that influence the effectiveness of B cell depletion for treatment of autoimmune diseases.

The possible role of CD4⁺CD25(high)Foxp3⁺/CD4⁺IL-17A⁺ cell imbalance in the autoimmunity of patients with Hashimoto thyroiditis

Hashimoto thyroiditis (HT) is a prototypic organ-specific autoimmune thyroid disease, for which the exact etiology remains unclear. The aim of this study was to investigate dynamic changes in regulatory T cell (Treg) and T helper 17 cell (Th17) populations in patients with HT at different stages of thyroid dysfunction, as well as to analyze the possible correlation between the Treg/Th17 cell axis and autoimmune status in HT. We assessed thyroid function and autoantibody serology both in HT patients and in healthy controls (HCs) and divided HT patients into three subgroups according to thyroid function. We then determined the percentages of Treg and Th17 cells in peripheral blood mononuclear cells and analyzed mRNA expression of the Treg and Th17 cell-defining transcription factors Foxp3 and RORγt. In addition, serum levels of TGF-β and IL-17A were assessed. We found that the percentage of Treg cells, Foxp3 mRNA levels, and the ratio of Treg/Th17 cells were all significantly lower in HT patients, while Th17 cell percentages and RORγt mRNA levels were significantly higher. Interestingly, we also observed significant differences in these measurements between HT patient subgroups. Serum IL-17A levels were markedly increased in HT patients, while serum concentrations of TGF-β were lower, compared to HCs. The ratio of Treg/Th17 cells was negatively correlated with the levels of serum thyroperoxidase antibody, thyroglobulin antibody, and thyrotropin (TSH) in HT patients. Taken together, our data suggest that the balance between Treg and Th17 cells shifts in favor of Th17 cells during clinical progression of HT, which is negatively correlated with levels of thyroid-specific autoantibodies and TSH, implying that Treg/Th17 cell imbalance may contribute to thyroid damage in HT.

Depletion of regulatory T-cells leads to moderate B-cell antigenicity in respiratory syncytial virus infection

OBJECTIVES

The regulation of the immunopathology of respiratory syncytial virus (RSV) by regulatory T-cells (CD4(+)CD25(+)Foxp3(+); Tregs) is not understood.

METHODS

To deduce the same, Tregs were depleted in BALB/c mice by injecting anti-CD25 antibody followed by RSV infection (anti-CD25-RSV mice).

RESULTS

In this model, a decrease in anti-fusion (F) antibody and neutralizing activity, and an increase in anti-nucleocapsid (N) antibody in serum, were seen. Decreased antibody-dependent cell-mediated cytotoxicity (ADCC) activity, increased IgG2a, and an influx of activated CD8(+) T-cells into the lungs were also observed. Co-culture of splenic CD45RA(+) B-cells from RSV-infected normal mice with CD4(+) cells isolated from anti-CD25-RSV mice (B/CD4) increased anti-F antibody secretion. The inclusion of CD25(+) Tregs isolated from isotype Ig-RSV mice into the B/CD4 co-culture substantially enhanced the frequency of anti-F antibody production. However, the same effect was not seen in the co-culture of CD45RA(+) B-cells with dendritic cells (DCs) (B/DCs) or CD8(+) cells (B/CD8) that were obtained from anti-CD25-RSV mice. The transfer of enriched B-cells from anti-CD25-RSV mice into RSV-infected SCID mice increased severe lung inflammation associated with the increased viral load and eosinophil number.

CONCLUSIONS

These results indicate that Tregs modulate B-cell activity, particularly in producing F-specific neutralizing antibodies, to regulate RSV-mediated exacerbated diseases.

Genes and environment as predisposing factors in autoimmunity: acceleration of spontaneous thyroiditis by dietary iodide in NOD.H2(h4) mice

In the field of autoimmune thyroiditis, NOD.H2(h4) mice have attracted significant and increasing attention since they not only develop spontaneous disease but they present thyroiditis with accelerated incidence and severity if they ingest iodide through their drinking water. This animal model highlights the interplay between genetic and dietary factors in the triggering of autoimmune disease and offers new opportunities to study immunoregulatory parameters influenced by both genes and environment. Here, we review experimental findings with this mouse model of thyroiditis.

Does microbiota composition affect thyroid homeostasis?

The intestinal microbiota is essential for the host to ensure digestive and immunologic homeostasis. When microbiota homeostasis is impaired and dysbiosis occurs, the malfunction of epithelial barrier leads to intestinal and systemic disorders, chiefly immunologic and metabolic. The role of the intestinal tract is crucial in the metabolism of nutrients, drugs, and hormones, including exogenous and endogenous iodothyronines as well as micronutrients involved in thyroid homeostasis. However, the link between thyroid homeostasis and microbiota composition is not yet completely ascertained. A pathogenetic link with dysbiosis has been described in different autoimmune disorders but not yet fully elucidated in autoimmune thyroid disease which represents the most frequent of them. Anyway, it has been suggested that intestinal dysbiosis may trigger autoimmune thyroiditis. Furthermore, hypo- and hyper-thyroidism, often of autoimmune origin, were respectively associated to small intestinal bacterial overgrowth and to changes in microbiota composition. Whether some steps of this thyroid network may be affected by intestinal microbiota composition is briefly discussed below.

Regulatory T cells in B-cell-deficient and wild-type mice differ functionally and in expression of cell surface markers

NOD.H-2h4 mice develop spontaneous autoimmune thyroiditis (SAT) with chronic inflammation of thyroids by T and B cells. B-cell deficient (B(-/-) ) mice are resistant to SAT but develop SAT if regulatory T (Treg) cells are transiently depleted. We established a transfer model using splenocytes from CD28(-/-)  B(-/-) mice (effector cells and antigen-presenting cells) cultured with or without sorted Treg cells from Foxp3-GFP wild-type (WT) or B(-/-) mice. After transfer to mice lacking T cells, mice given Treg cells from B(-/-) mice had significantly lower SAT severity scores than mice given Treg cells from WT mice, indicating that Treg cells in B(-/-) mice are more effective suppressors of SAT than Treg cells in WT mice. Treg cells from B(-/-) mice differ from WT Treg cells in expression of CD27, tumour necrosis factor receptor (TNFR) II p75, and glucocorticoid-induced TNFR-related protein (GITR). After transient depletion using anti-CD25 or diphtheria toxin, the repopulating Treg cells in B(-/-) mice lack suppressor function, and expression of CD27, GITR and p75 is like that of WT Treg cells. If B(-/-) Treg cells develop with B cells in bone marrow chimeras, their phenotype is like that of WT Treg cells. Addition of B cells to cultures of B(-/-) Treg and T effector cells abrogates their suppressive function and their phenotype is like that of WT Treg cells. These results establish for the first time that Treg cells in WT and B(-/-) mice differ both functionally and in expression of particular cell surface markers. Both properties are altered after transient depletion and repopulation of B(-/-) Treg cells, and by the presence of B cells during Treg cell development or during interaction with effector T cells.

What Causes Biliary Atresia? Unique Aspects of the Neonatal Immune System Provide Clues to Disease Pathogenesis

Biliary atresia (BA) is the most frequent identifiable cause of neonatal cholestasis and the majority of patients will need liver transplantation for survival. Despite surgical intervention with the Kasai portoenterostomy, significant fibrosis and cirrhosis develops early in life. An increased understanding of what causes this inflammatory fibrosing cholangiopathy will lead to therapies aimed at protecting the intrahepatic biliary system from immune-mediated damage. This review focuses on studies pertaining to the role of the adaptive immune response in bile duct injury in BA, including cellular and humoral immunity. The neonatal presentation of BA begs the question of what are potential modifications of unique aspects of the neonatal immune system that "sets the stage" for the progressive biliary disease? Throughout this article, characteristics of the neonatal immune response are outlined and theories as to how alterations of this response could contribute to the pathogenesis of BA are discussed. These include aberrant Th1 and Th17 responses, deficiencies in regulatory T cells, activation of humoral immunity and autoimmunity. In order to advance our understanding of the etiology of BA, future studies should focus on those unique aspects of the neonatal immune system that have gone awry, as detailed throughout this review.

NOD.H-2h4 mice: an important and underutilized animal model of autoimmune thyroiditis and Sjogren's syndrome

NOD.H-2h4 mice express the K haplotype on the NOD genetic background. They spontaneously develop thyroiditis and Sjogren's syndrome, but they do not develop diabetes. Although autoimmune thyroid diseases and Sjogren's syndrome are highly prevalent autoimmune diseases in humans, there has been relatively little emphasis on the use of animal models of these diseases for understanding basic mechanisms involved in development and therapy of chronic organ-specific autoimmune diseases. The goal of this review is to highlight some of the advantages of NOD.H-2h4 mice for studying basic mechanisms involved in development of autoimmunity. NOD.H-2h4 mice are one of relatively few animal models that develop organ-specific autoimmune diseases spontaneously, i.e., without a requirement for immunization with antigen and adjuvant, and in both sexes in a relatively short period of time. Thyroiditis and Sjogren's syndrome in NOD.H-2h4 mice are chronic autoimmune diseases that develop relatively early in life and persist for the life of the animal. Because the animals do not become clinically ill, the NOD.H-2h4 mouse provides an excellent model to test therapeutic protocols over a long period of time. The availability of several mutant mice on this background provides a means to address the impact of particular cells and molecules on the autoimmune diseases. Moreover, to our knowledge, this is the only animal model in which the presence or absence of a single cytokine, IFN-γ, is sufficient to completely inhibit one autoimmune thyroid disease, with a completely distinct autoimmune thyroid disease developing when it is absent.

Hashimoto's thyroiditis and papillary thyroid cancer: are they immunologically linked?

Hashimoto's thyroiditis (HT) is the most common autoimmune disease in humans frequently leading to hypothyroidism. HT is characterized by a cellular immune response with lymphatic infiltration of the thyroid gland by T and B cells, as well as by a humoral immune response leading to specific antibody production. The synchronous appearance of HT and papillary thyroid cancer (PTC) indicates an immunological link between the two entities. Three different pathomechanisms may be postulated, including preexisting autoimmunity leading to malignancy due to inflammation, immunity towards preexisiting tumor cells leading to specific autoimmunity, and immune tolerance leading to malignancy despite (auto)immunity. In this article we review data describing these potential mechanisms that might lead to the synchronous appearance of HT and PTC.

Breaking tolerance to thyroid antigens: changing concepts in thyroid autoimmunity

Thyroid autoimmunity involves loss of tolerance to thyroid proteins in genetically susceptible individuals in association with environmental factors. In central tolerance, intrathymic autoantigen presentation deletes immature T cells with high affinity for autoantigen-derived peptides. Regulatory T cells provide an alternative mechanism to silence autoimmune T cells in the periphery. The TSH receptor (TSHR), thyroid peroxidase (TPO), and thyroglobulin (Tg) have unusual properties ("immunogenicity") that contribute to breaking tolerance, including size, abundance, membrane association, glycosylation, and polymorphisms. Insight into loss of tolerance to thyroid proteins comes from spontaneous and induced animal models: 1) intrathymic expression controls self-tolerance to the TSHR, not TPO or Tg; 2) regulatory T cells are not involved in TSHR self-tolerance and instead control the balance between Graves' disease and thyroiditis; 3) breaking TSHR tolerance involves contributions from major histocompatibility complex molecules (humans and induced mouse models), TSHR polymorphism(s) (humans), and alternative splicing (mice); 4) loss of tolerance to Tg before TPO indicates that greater Tg immunogenicity vs TPO dominates central tolerance expectations; 5) tolerance is induced by thyroid autoantigen administration before autoimmunity is established; 6) interferon-α therapy for hepatitis C infection enhances thyroid autoimmunity in patients with intact immunity; Graves' disease developing after T-cell depletion reflects reconstitution autoimmunity; and 7) most environmental factors (including excess iodine) "reveal," but do not induce, thyroid autoimmunity. Micro-organisms likely exert their effects via bystander stimulation. Finally, no single mechanism explains the loss of tolerance to thyroid proteins. The goal of inducing self-tolerance to prevent autoimmune thyroid disease will require accurate prediction of at-risk individuals together with an antigen-specific, not blanket, therapeutic approach.

Follicular B cells in thyroids of mice with spontaneous autoimmune thyroiditis contribute to disease pathogenesis and are targets of anti-CD20 antibody therapy

B cells are required for development of spontaneous autoimmune thyroiditis (SAT) in NOD.H-2h4 mice where they function as important APCs for activation of CD4(+) T cells. Depletion of B cells using anti-CD20 effectively inhibits SAT development. The goals of this study were to characterize the B cells that migrate to thyroids in SAT, and to determine whether anti-CD20 effectively targets those B cells in mice with established SAT. The results showed that most thyroid-infiltrating B cells in mice with SAT are follicular (FO) B cells. Expression of CD80, CD86, and CD40 was significantly increased on FO, but not marginal zone, splenic B cells after SAT development. Thyroid-infiltrating and peripheral blood B cells had lower expresion of CD20 and CD24 compared with splenic and lymph node FO B cells. Despite reduced CD20 expression, anti-CD20 depleted most B cells in thyroids of mice with established SAT within 3 d. B cell depletion in thyroids of mice given anti-CD20 was more complete and longer lasting than in spleen and lymph nodes and was comparable to that in blood. Circulation of B cells was required for effective and rapid removal of B cells in thyroids because preventing lymphocyte egress by administration of FTY720 abrogated the effects of anti-CD20 on thyroid B cells. Therefore, the FO subset of B cells preferentially contributes to SAT development and persistence, and anti-CD20 targeting of FO B cells effectively eliminates B cells in the target organ even though thyroid B cells have decreased CD20 expression.

Circulating T follicular helper cell and regulatory T cell frequencies are influenced by B cell depletion in patients with granulomatosis with polyangiitis

OBJECTIVE

Granulomatosis with polyangiitis (GPA) is a rare and sometimes fatal systemic autoimmune disease. ANCAs specific for PR3 are associated with GPA. Remission in GPA can be achieved through B cell depletion (BCD) therapy. Our aim was to understand whether the frequencies of T cell subsets are influenced by BCD.

METHODS

The frequencies of circulating T follicular helper cells (cTFHs) and regulatory T cells (Tregs) from 36 GPA patients including 11 rituximab-treated patients and 10 healthy controls were studied by flow cytometry. The functional capacity of Tregs was assessed by in vitro co-culture assays.

RESULTS

We observed an increased frequency of cTFHs and a reduced frequency of antigen-experienced Tregs in peripheral blood from GPA patients on conventional therapies but not in those treated with rituximab compared with healthy controls. Furthermore, the ratio of cTFHs to Tregs was significantly higher in GPA patients on conventional therapies than in GPA patients treated with rituximab who were clinically improved or controls. Whereas Tregs were numerically reduced in GPA patients on conventional therapy, the suppressive capacity of Tregs on a per cell basis was not significantly altered in these individuals.

CONCLUSION

Our study illustrated increased cTFHs with decreased antigen-experienced Tregs in GPA patients on conventional therapies, but in B cell-depleted patients the levels of cTFHs and Tregs were similar to healthy controls. The negative correlation between cTFHs and Tregs implies the balance between T cell subsets and its B cell dependence impact on disease activity in GPA.

Reduced effectiveness of CD4+Foxp3+ regulatory T cells in CD28-deficient NOD.H-2h4 mice leads to increased severity of spontaneous autoimmune thyroiditis

NOD.H-2h4 mice given NaI in their drinking water develop iodine-accelerated spontaneous autoimmune thyroiditis (ISAT) with chronic inflammation of the thyroid by T and B cells and production of anti-mouse thyroglobulin (MTg) autoantibody. CD28(-/-) NOD.H-2h4 mice, which have reduced numbers of CD4(+)Foxp3(+) regulatory T cells (Tregs), were developed to examine the role of Tregs in ISAT development. CD28(-/-) NOD.H2-h4 mice develop more severe ISAT than do wild-type (WT) mice, with collagen deposition (fibrosis) and low serum T4. CD28(-/-) mice have increased expression of proinflammatory cytokines IFN-γ and IL-6, consistent with increased mononuclear cell infiltration and tissue destruction in thyroids. Importantly, transferring purified CD4(+)Foxp3(+) Tregs from WT mice reduces ISAT severity in CD28(-/-) mice without increasing the total number of Tregs, suggesting that endogenous Tregs in CD28(-/-) mice are functionally ineffective. Endogenous CD28(-/-) Tregs have reduced surface expression of CD27, TNFR2 p75, and glucocorticoid-induced TNFR-related protein compared with transferred CD28(+/+) Tregs. Although anti-MTg autoantibody levels generally correlate with ISAT severity scores in WT mice, CD28(-/-) mice have lower anti-MTg autoantibody responses than do WT mice. The percentages of follicular B cells are decreased and those of marginal zone B cells are increased in spleens of CD28(-/-) mice, and they have fewer thyroid-infiltrating B cells than do WT mice. This suggests that CD28 deficiency has direct and indirect effects on the B cell compartment. B cell-deficient (B(-/-)) NOD.H-2h4 mice are resistant to ISAT, but CD28(-/-)B(-/-) mice develop ISAT comparable to WT mice and have reduced numbers of Tregs compared with WT B(-/-) mice.

B cell deficient mice are protected from biliary obstruction in the rotavirus-induced mouse model of biliary atresia

A leading theory regarding the pathogenesis of biliary atresia (BA) is that bile duct injury is initiated by a virus infection, followed by an autoimmune response targeting bile ducts. In experimental models of autoimmune diseases, B cells have been shown to play an important role. The aim of this study was to determine the role of B cells in the development of biliary obstruction in the Rhesus rotavirus (RRV)-induced mouse model of BA. Wild-type (WT) and B cell-deficient (Ig-α(-/-)) mice received RRV shortly after birth. Ig-α(-/-) RRV-infected mice had significantly increased disease-free survival rate compared to WT RRV-infected BA mice (76.8% vs. 17.5%). In stark contrast to the RRV-infected BA mice, the RRV-infected Ig-α(-/-) mice did not have hyperbilirubinemia or bile duct obstruction. The RRV-infected Ig-α(-/-) mice had significantly less liver inflammation and Th1 cytokine production compared to RRV-infected WT mice. In addition, Ig-α(-/-) mice had significantly increased numbers of regulatory T cells (Tregs) at baseline and after RRV infection compared to WT mice. However, depletion of Tregs in Ig-α(-/-) mice did not induce biliary obstruction, indicating that the expanded Tregs in the Ig-α(-/-) mice were not the sole reason for protection from disease. Conclusion : B cell deficient Ig-α(-/-) mice are protected from biliary obstruction in the RRV-induced mouse model of BA, indicating a primary role of B cells in mediating disease pathology. The mechanism of protection may involve lack of B cell antigen presentation, which impairs T-cell activation and Th1 inflammation. Immune modulators that inhibit B cell function may be a new strategy for treatment of BA.

B cells assist allograft rejection in the deficiency of protein kinase c-theta

We have previously shown that mice deficient in protein kinase C theta (PKCθ) have the ability to reject cardiac allografts, but are susceptible to tolerance induction. Here we tested role of B cells in assisting alloimmune responses in the absence of PKCθ. Mouse cardiac allograft transplantations were performed from Balb/c (H-2d) to PKCθ knockout (PKCθ(-/-)), PKCθ and B cell double-knockout (PBDK, H-2b) mice and wild-type (WT) C57BL/6 (H-2b) mice. PBDK mice spontaneously accepted the allografts with the inhibition of NF-κB activation in the donor cardiac allograft. Anti-B cell antibody (rituximab) significantly delayed allograft rejection in PKCθ(-/-), but not in WT mice. Co-transfer of PKCθ(-/-) T plus PKCθ(-/-) B cells or primed sera triggered allograft rejection in Rag1(-/-) mice, and only major histocompatibility complex class II-enriched B cells, but not class I-enriched B cells, were able to promote rejection. This, together with the inability of PKCθ(-/-) and CD28(-/-) double-deficient (PCDK) mice to acutely reject allografts, suggested that an effective cognate interaction between PKCθ(-/-) T and B cells for acute rejection is CD28 molecule dependent. We conclude that T-B cell interactions synergize with PKCθ(-/-) T cells to mediate acute allograft rejection.

Transient depletion of CD4+ CD25+ regulatory T cells results in multiple autoimmune diseases in wild-type and B-cell-deficient NOD mice

Approximately 80% of female wild-type non-obese diabetic (WT NOD) mice spontaneously develop diabetes, whereas B-cell-deficient (B(-/-)) NOD mice are resistant to diabetes. B(-/-) mice are also resistant to other spontaneous and experimentally induced autoimmune diseases, including arthritis, systemic lupus erythematosus, Sjögren syndrome and thyroiditis. Under normal conditions, activation of self-reactive T cells in the periphery is limited by CD4(+) CD25(+) natural regulatory T (Treg) cells. B(-/-) NOD.H-2h4 mice, normally resistant to spontaneous autoimmune thyroiditis (SAT), develop SAT when Treg cells are depleted, suggesting that Treg cells are preferentially activated when autoantigen is initially presented by non-B-cell antigen-presenting cells. To test the hypothesis that increased Treg cell activity in B(-/-) mice contributes to their resistance to other autoimmune diseases, WT and B(-/-) NOD mice were given anti-CD25 to transiently deplete CD4(+) CD25(+) Treg cells. The WT and B(-/-) NOD mice given anti-CD25 developed diabetes much earlier than WT mice given rat IgG, whereas rat IgG-treated B(-/-) mice did not develop diabetes. Treg-cell-depleted mice had increased lymphocyte infiltration of the pancreas, salivary glands and thyroid compared with controls given rat IgG. These results are consistent with the hypothesis that resistance of B-cell-deficient NOD mice to several autoimmune diseases is due to the activity of Treg cells.

Effects of green tea polyphenols on iodide-induced autoimmune thyroiditis in nonobese diabetic mice

Because green tea polyphenols (GTPs) possess anti-inflammatory properties and are effective in inhibiting autoimmune diseases in experimental settings, we examined whether GTPs prevented the development of autoimmune thyroiditis in iodide-treated nonobese diabetic (NOD) mice, an animal model of Hashimoto's thyroiditis (HT). Mice were given 0.05% iodide water or iodide water supplemented with 0.2% GTPs for 8 weeks. GTPs administration led to an enhanced production of interleukin-10 by concanavalin A-stimulated splenocytes but did not interfere with thyroiditis development. Serum thyroxine levels were not influenced by GTPs. Our data suggest that administration of GTPs may not be an effective strategy for the prevention of HT.

Clues to the etiology of bile duct injury in biliary atresia

Biliary atresia (BA) is an infantile obstructive cholangiopathy of unknown etiology with suboptimal therapy, which is responsible for 40 to 50% of all pediatric liver transplants. Although the etiology of bile duct injury in BA in unknown, it is postulated that a pre- or perinatal viral infection initiates cholangiocyte apoptosis and release of antigens that trigger a Th1 immune response that leads to further bile duct injury, inflammation, and obstructive fibrosis. Humoral immunity and activation of the innate immune system may also play key roles in this process. Moreover, recent investigations from the murine BA model and human data suggest that regulatory T cells and genetic susceptibility factors may orchestrate autoimmune mechanisms. What controls the coordination of these events, why the disease only occurs in the first few months of life, and why a minority of infants with perinatal viral infections develop BA are remaining questions to be answered.

Regulatory B cells play a key role in immune system balance

Regulatory B cells (Bregs) may act earlier than regulatory T cells (Tregs) and may play as important a role in autoimmune and allergic diseases. Obstacles to the investigation of Bregs are the same as those encountered for Tregs: the regulatory effects are short-lived in some cases, there is no consistent phenotype (C5 expression is neither indispensable nor sufficient), differences exist across species (e.g., between humans and mice), and there are a number of suppression modalities (IL-10, TGF-beta, expression of proapoptotic membrane molecules) that vary across Breg subtypes. The Breg subtypes may be homologous to the Treg subtypes (Br1 cells expressing IL-10, Br3 cells expressing TGF-beta, and B-Foxp3 cells), although the Br1 subtype seems to predominate. Nevertheless, differences with Treg cells may exist: Breg activation may chiefly involve the toll-like receptors rather than the antigen receptor; and Bregs act earlier, facilitating the recruitment of Tregs then disappearing once the Tregs become operational. Bregs make a major contribution to autoimmune disorders associated with several forms of immune deficiency, as well as to the absence of transplant rejection when there is a strong B cell response. Breg deficiencies have been reported in lupus, and the disappointing effects in this disease of treatments designed to inhibit the B cell response may be related to further Breg impairment. In several animal models, Breg stimulation is effective in correcting a variety of autoimmune disorders, most notably those initiated in the mucous membranes. Research into the interactions between the gut microbiota and Bregs holds considerable promise.

Unraveling effector functions of B cells during infection: the hidden world beyond antibody production

Antibodies made by B cells are critically important for immune protection to a variety of infectious agents. However, it is becoming increasingly clear that B cells do more than make antibodies and that B cells can both enhance and suppress immune responses. Furthermore, there is growing evidence that B cells modulate cellular immune responses by antibody dependent and independent mechanisms. Although we have a good understanding of the roles played by antibody- secreting effector B cells during immune responses, we know very little about the Ab independent "effector" functions of B cells in either health or disease. Given the recent data suggesting that B cells may contribute to autoimmune disease pathogenesis via an antibody independent mechanism and the increasing use of B cell depletion therapy in autoimmune patients, investigators are beginning to reassess the multiple roles for B cells during immune responses. In this article, we review data describing how B cells mediate protection to pathogens independently of antibody production. In particular, we will focus on the role that B cells play in facilitating dendritic cell and T cell interactions in lymph nodes, the importance of antigen-presenting B cells in sustaining effector T cell and T follicular helper responses to pathogens and the relevance of cytokine-producing effector and regulatory B cells in immune responses.

Transient depletion of B cells in young mice results in activation of regulatory T cells that inhibit development of autoimmune disease in adults

B-cell depletion therapy can be effective for treating B-cell lymphomas as well as many human and murine autoimmune diseases. B-cell-deficient mice are normally resistant to spontaneous autoimmune thyroiditis (SAT), but they develop SAT if regulatory T cells are transiently depleted during the first 3-6 weeks after birth. This was also a critical time when B-cell depletion effectively inhibited development of SAT in adult mice. The current study was undertaken to test the hypothesis that transient depletion of B cells using anti-CD20 would be sufficient to suppress SAT if B cells were depleted early in life and that inhibition of SAT would be due to the activity of Treg that functioned most effectively when B cells were absent or low. The results presented here support this hypothesis and indicate that development of autoimmune disease in adults is effectively inhibited when anti-CD20 is administered 1-3 weeks after birth. After 3 weeks, transient B-cell depletion is no longer effective, and B-cell depletion must be maintained to effectively suppress autoimmune disease. B-cell depletion in 1- to 3-week-old mice depletes all B-cell subsets, whereas B-cell depletion initiated in adults spares many marginal zone B cells. Following early B-cell depletion, splenic Treg increase in number, and depletion of Treg reverses the inhibitory effect of anti-CD20 on disease development. Early transient depletion of B cells could be useful for preventing autoimmune disease in individuals at high risk for developing autoimmune diseases as adults.

Dynamic changes of CD4+CD25 + regulatory T cells in NOD.H-2h4 mice with iodine-induced autoimmune thyroiditis

Iodine is an essential trace element for thyroid hormone synthesis and metabolism, either low or high intake may lead to thyroid disease, but the pathogenetic mechanisms by which iodine interacts with the thyroid autoimmune are poorly understood. We investigated the dynamic changes of CD4(+)CD25(+) regulatory T cells in NOD.H-2(h4) mice with iodine-induced autoimmune thyroiditis (AIT), and explore potential immune mechanism of AIT induced by iodine. NOD.H-2(h4) mice were randomly divided into two groups, and received plain water or water containing 0.005% sodium iodide. Eight weeks after iodine provision, the incidences of thyroiditis, relative weights of thyroids, and serum thyroglobulin antibody titers in the iodine-supplied groups were significantly increased compared to the control groups (p < 0.05). The AIT mice had fewer CD4(+)CD25(+)Foxp3(+) T cells and reduced Foxp3 mRNA expression in splenocytes compared with the controls (p < 0.01), and maintained relatively low levels during the development of thyroiditis. The changes described above aggravated gradually with the extension of iodine treatment. These data suggest that CD4(+)CD25(+) regulatory T cells may be involved in the pathogenesis and development of AIT induced by iodine.

B cell depletion enhances T regulatory cell activity essential in the suppression of arthritis

The efficacy of B cell-depletion therapy in rheumatoid arthritis has driven interest in understanding the mechanism. Because the decrease in autoantibodies in rheumatoid arthritis does not necessarily correlate with clinical outcome, other mechanisms may be operative. We previously reported that in proteoglycan-induced arthritis (PGIA), B cell-depletion inhibits autoreactive T cell responses. Recent studies in B cell-depletion therapy also indicate a role for B cells in suppressing regulatory mechanisms. In this study, we demonstrate that B cells inhibited both the expansion and function of T regulatory (Treg) cells in PGIA. Using an anti-CD20 mAb, we depleted B cells from mice with PGIA and assessed the Treg cell population. Compared to control Ab-treated mice, Treg cell percentages were elevated in B cell-depleted mice, with a higher proportion of CD4(+) T cells expressing Foxp3 and CD25. On a per-cell basis, CD4(+)CD25(+) cells from B cell-depleted mice expressed increased amounts of Foxp3 and were significantly more suppressive than those from control Ab-treated mice. The depletion of Treg cells with an anti-CD25 mAb concurrent with B cell-depletion therapy restored the severity of PGIA to levels equal to untreated mice. Although titers of autoantibodies did not recover to untreated levels, CD4(+) T cell recall responses to the immunizing Ag returned as measured by T cell proliferation and cytokine production. Thus, B cells have the capacity to regulate inflammatory responses by enhancing effector T cells along with suppressing Treg cells.

Regulatory T cells in CNS injury: the simple, the complex and the confused

Regulatory CD4(+)CD25(+)Foxp3(+) T cells (Tregs) have been the focus of significant attention for their role in controlling immune responses. Although knowledge of Treg biology has burgeoned, wide gaps remain in our understanding of Treg function under both normal and pathological conditions. Pioneering studies demonstrated roles for Tregs in cancer and autoimmune diseases, including experimental autoimmune encephalitis, and this knowledge is often applied to other pathologies including neurodegenerative conditions. However, differences between immunity in neurodegeneration and in malignancy or autoimmunity are often neglected. Thus, Treg manipulations in central nervous system (CNS) neurodegenerative conditions often yield unexpected outcomes. In this piece, we explore how the immunology of neurodegeneration differs from that of cancer and autoimmunity and how these differences create confusion about the role of Tregs in neurodegenerative conditions.

Rituximab therapy for autoimmune haematological diseases

Autoimmune haematological diseases are characterized by the production of antibodies against blood proteins or cells, and comprise primary immune thrombocytopenia, autoimmune haemolytic anaemia, acquired haemophilia, and thrombotic thrombocytopenic purpura. Current treatments for these disorders include corticosteroids, cytotoxic drugs and splenectomy, which may be associated with significant systemic toxicity and/or morbility. B cells play a key role in both the development and perpetuation of autoimmunity, since they produce autoantibodies but also function as antigen-presenting cells, and release immunomodulatory cytokines. Rituximab, an anti-CD20 monoclonal antibody that specifically depletes B cells, may be an effective treatment strategy for patients with autoimmune disorders. This article reviews data of the literature, showing that patients with autoimmune haematological diseases can respond to rituximab irrespective of age and number or type of prior treatments. These data suggest that rituximab provides an effective and well-tolerated treatment option for these conditions.

B cell depletion in autoimmune diabetes: insights from murine models

INTRODUCTION

The incidence of type 1 diabetes (T1D) is rising for reasons that largely elude us. New strategies aimed at halting the disease process are needed. One type of immune cell thought to contribute to T1D is the B lymphocyte. The first Phase II trial of B cell depletion in new onset T1D patients indicated that this slowed the destruction of insulin-producing pancreatic beta cells. The mechanistic basis of the beneficial effects remains unclear.

AREAS COVERED

Studies of B cell depletion and deficiency in animal models of T1D. How B cells can influence T cell-dependent autoimmune diabetes in animal models. The heterogeneity of B cell populations and current evidence for the potential contribution of specific B cell subsets to diabetes, with emphasis on marginal zone B cells and B1 B cells.

EXPERT OPINION

B cells can influence the T cell response to islet antigens and B cell depletion or genetic deficiency is associated with decreased insulitis in animal models. New evidence suggests that B1 cells may contribute to diabetes pathogenesis. A better understanding of the roles of individual B cell subsets in disease will permit fine-tuning of therapeutic strategies to modify these populations.

Prolonged infection by Fonsecaea pedrosoi after antigenic co-stimulation at different sites in experimental murine chromoblastomycosis

In the present study, we examined prolonged infection after antigenic co-stimulation by inoculation of the fungus Fonsecaea pedrosoi at two different sites in three mouse strains (BALB/c, Swiss, and C57BL/6). Using this murine model of infection, we showed that antigen induction of infection at more than one site led to a local suppression of active lesions, which increased the time course of experimental chromoblastomycosis (CBM). Footpad infection with a simultaneous infection of the peritoneum or a mucosal site appeared to cause prolonged infection and frequent fungal disseminations. Using knockout (KO) mice, we observed that antigenic co-stimulation caused progressive illness in CD8-KO animals and an effective immune response in the absence of IL-10. In Xid mice, co-stimulation provoked chronic infection (not prolonged), suggesting that B1 B cells play an important role in the control of fungal infection. The tissue response to infection was similar in all co-stimulated mouse groups, as anatomopathologic sections revealed multifocal lesions (granuloma-like). In general, these mice had acute responses at primary antigenic sites with an intense migration of polymorphonuclear leukocytes (PMNs), whereas the distant infection sites (footpad) showed signs of chronic infection. The migration of PMNs to the secondary site (footpad) increased in the later periods of infection, especially after the disappearance of the primary antigenic focus. PMN migration was associated with lesion-dormancy breakage and fungal elimination. Our findings suggest that the host inflammatory/suppression mechanisms induced by antigenic co-stimulation to systemically fight the same pathogen act coordinately through responses that differ at the sites of infection between acute and chronic integrated healing processes that are more prolonged than an acute infection at a single site. However, the long persistence of fungal cells in the host may be linked to microbial adaptation to a parasitic infection as observed in co-stimulated Xid mice.

Transgenic expression of TGF-beta on thyrocytes inhibits development of spontaneous autoimmune thyroiditis and increases regulatory T cells in thyroids of NOD.H-2h4 mice

Transgenic NOD.H-2h4 mice expressing TGF-beta under control of the thyroglobulin promoter were generated to assess the role of TGF-beta in the development of thyrocyte hyperplasia. In contrast to nontransgenic littermates, which develop lymphocytic spontaneous autoimmune thyroiditis (L-SAT), all TGF-beta transgenic (Tg) mice given NaI water for 2-7 mo developed thyroid lesions characterized by severe thyroid epithelial cell hyperplasia and proliferation, with fibrosis and less lymphocyte infiltration than in nontransgenic mice. Most Tg mice produced less anti-mouse thyroglobulin autoantibody than did wild type (WT) mice. T cells from Tg and WT mice were equivalent in their ability to induce L-SAT after transfer to SCID or TCRalpha(-/-) mice. WT lymphocytes could transfer experimental autoimmune thyroiditis or L-SAT to Tg mice, indicating that the transgenic environment did not prevent migration of lymphocytes to the thyroid. Thyroids of Tg mice had higher frequencies of Foxp3(+) regulatory T cells (Tregs) compared with nontransgenic WT mice. Transient depletion of Tregs by anti-CD25 resulted in increased infiltration of inflammatory cells into thyroids of transgenic mice. Treg depletion also resulted in increased anti-mouse thyroglobulin autoantibody responses and increased expression of IFN-gamma and IFN-gamma-inducible chemokines in thyroids of Tg mice. The results suggest that spontaneous autoimmune thyroiditis is inhibited in mice expressing transgenic TGF-beta on thyrocytes, at least in part, because there is an increased frequency of Tregs in their thyroids.

Selenium upregulates CD4(+)CD25(+) regulatory T cells in iodine-induced autoimmune thyroiditis model of NOD.H-2(h4) mice

Selenium (Se) is required for thyroid hormone synthesis and metabolism. Se treatment reduces serum thyroidspecific antibody titers in patients with autoimmune thyroiditis (AIT), but the exact mechanism is not clear. We investigated the effects of Se treatment on CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) in a iodine-induced autoimmune thyroiditis model. NOD.H-2(h4) mice were randomly divided into control, AIT untreated, and AIT with Se treatment groups. Mice were fed with 0.005% sodium iodine (NaI) water for 8 weeks to induce AIT. Se-treated mice received 0.3 mg/L sodium selenite in drinking water. The AIT mice had fewer Treg cells and reduced Foxp3 mRNA expression in splenocytes compared with the controls (p < 0.01). The percentage of Treg cells and expression of Foxp3 mRNA were increased by Se treatment (as compared with untreated AIT mice, p < 0.05). Mice that received Se supplementation also had lower serum thyroglobulin antibody (TgAb) titers and reduced lymphocytic infiltration in thyroids than untreated AIT mice. These data suggest that CD4(+)CD25(+) T cells play an important role in the development of AIT. Se supplementation may restore normal levels of CD4(+)CD25(+) T cells by up-regulating the expression of Foxp3 mRNA in mice with AIT.

A cellular viewpoint of anti-FVIII immune response in hemophilia A

A large proportion of hemophilia A patients who receive replacement therapy, develop an immune response toward the infused factor VIII (FVIII). In this review, we discuss recent progress in several aspects of the anti-FVIII immune response, focusing on the sites of FVIII endocytosis (marginal zone of the spleen and bleeding site), the type of antigen-presenting cells (dendritic cells, macrophages and B cells) and endocytic receptors, implicated in FVIII presentation to T cells during primary and secondary immune response. Although it is becoming increasingly clear that regulatory T cells are involved in FVIII tolerance in healthy subjects and potentially in patients without inhibitors, we would like to demonstrate that little is known about the different T cells subsets and the cytokines network, which are also crucial for the development of allo- and autoimmune diseases. As more information on these issues becomes available, a better understanding of the role of each immune cells compartment in promoting FVIII tolerance or inhibitors development might lead to new strategies to promote FVIII tolerance in hemophilia A patients.

CD4(+)CD25(+) T-cells control autoimmunity in the absence of B-cells

OBJECTIVE

Tumor necrosis factor ligand family members B-cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) can exert powerful effects on B-cell activation and development, type 1 T-helper cell (Th1) immune responses, and autoimmunity. We examined the effect of blocking BAFF and APRIL on the development of autoimmune diabetes.

RESEARCH DESIGN AND METHODS

Female NOD mice were administered B-cell maturation antigen (BCMA)-Fc from 9 to 15 weeks of age. Diabetes incidence, islet pathology, and T- and B-cell populations were examined.

RESULTS

BCMA-Fc treatment reduced the severity of insulitis and prevented diabetes development in NOD mice. BCMA-Fc-treated mice showed reduced follicular, marginal-zone, and T2MZ B-cells. B-cell reduction was accompanied by decreased frequencies of pathogenic CD4(+)CD40(+) T-cells and reduced Th1 cytokines IL-7, IL-15, and IL-17. Thus, T-cell activation was blunted with reduced B-cells. However, BCMA-Fc-treated mice still harbored detectable diabetogenic T-cells, suggesting that regulatory mechanisms contributed to diabetes prevention. Indeed, BCMA-Fc-treated mice accumulated increased CD4(+)CD25(+) regulatory T-cells (Tregs) with age. CD4(+)CD25(+) cells were essential for maintaining euglycemia because their depletion abrogated BCMA-Fc-mediated protection. BCMA-Fc did not directly affect Treg homeostasis given that CD4(+)CD25(+)Foxp3(+) T-cells did not express TACI or BR3 receptors and that CD4(+)CD25(+)Foxp3(+) T-cell frequencies were equivalent in wild-type, BAFF(-/-), TACI(-/-), BCMA(-/-), and BR3(-/-) mice. Rather, B-cell depletion resulted in CD4(+)CD25(+) T-cell-mediated protection from diabetes because anti-CD25 monoclonal antibody treatment precipitated diabetes in both diabetes-resistant NOD.microMT(-/-) and BCMA-Fc-treated mice.

CONCLUSIONS

BAFF/APRIL blockade prevents diabetes. BCMA-Fc reduces B-cells, subsequently blunting autoimmune activity and allowing endogenous regulatory mechanisms to preserve a prehyperglycemic state.

Inhibition of TGFbeta1 makes nonimmunogenic tumor cells effective for therapeutic vaccination

We have previously demonstrated that transplanted cells from the SW1 clone of the K1735 melanoma and the Ag104 sarcoma grow progressively in syngeneic C3H mice even after transfection to engage CD137, a procedure that increases the immunogenicity of many other tumors. We now show that SW1 and Ag104 cells produce high levels of transforming growth factor (TGF) beta1, and that they can induce an antitumor response if they are transfected with a nonreplicating lentivirus vector to "silence" the TGFbeta1 gene via short hairpin RNA. Importantly, vaccination with SW1 or Ag104 cells, which do not make TGFbeta1, is therapeutically efficacious against small wild type tumors, including SW1 micrometastases in the lung. An analogous approach may be applicable to human tumors that produce TGFbeta1 or other immunosuppressive molecules to improve the efficacy of tumor cell-based therapeutic vaccines.

B cells and immunological tolerance

Work from multiple groups continues to provide additional evidence for the powerful and highly diverse roles, both protective and pathogenic, that B cells play in autoimmune diseases. Similarly, it has become abundantly clear that antibody-independent functions may account for the opposing influences that B cells exercise over other arms of the immune response and ultimately over autoimmunity itself. Finally, it is becoming apparent that the clinical impact of B-cell depletion therapy may be, to a large extent, determined by the functional balance between different B-cell subsets that may be generated by this therapeutic intervention. In this review, we postulate that our perspective of B-cell tolerance and our experimental approach to its understanding are fundamentally changed by this view of B cells. Accordingly, we first discuss current knowledge of B-cell tolerance conventionally defined as the censoring of autoantibody-producing B cells (with an emphasis on human B cells). Therefore, we discuss a different model that contemplates B cells not only as targets of tolerance but also as mediators of tolerance. This model is based on the notion that the onset of clinical autoimmune disease may require a B-cell gain-of-pathogenic function (or a B-cell loss-of-regulatory-function) and that accordingly, disease remission may depend on the restoration of the physiological balance between B-cell pathogenic and protective functions.

Commonality in the genetic control of Type 1 diabetes in humans and NOD mice: variants of genes in the IL-2 pathway are associated with autoimmune diabetes in both species

Variants within the IL-2 (interleukin 2) and CD25 genes are associated with T1DM (Type 1 diabetes mellitus) in mice and humans respectively. Both gene products are essential for optimal immune tolerance and a partial failure to tolerize is linked to the autoimmune responses to insulin and other beta-cell proteins that precede T1DM onset. Gene variants that contribute to common disease susceptibility often alter gene expression only modestly. Small expression changes can be technically challenging to measure robustly, especially since biological variation usually contributes negatively to this goal. The present review focuses on allele-specific expression assays that can be used to quantify genotype-determined expression differences such as those observed for IL-2, where the susceptibility allele is transcribed 2-fold less than the resistance allele.