Adoptive transfer of autoimmune diabetes and thyroiditis to athymic rats

Visceral Adipose Tissue: A New Target Organ in Virus-Induced Type 1 Diabetes

Type 1 diabetes (T1D) is a proinflammatory pathology that leads to the specific destruction of insulin producing β-cells and hyperglycaemia. Much of the knowledge about type 1 diabetes (T1D) has focused on mechanisms of disease progression such as adaptive immune cells and the cytokines that control their function, whereas mechanisms linked with the initiation of the disease remain unknown. It has been hypothesized that in addition to genetics, environmental factors play a pivotal role in triggering β-cell autoimmunity. The BioBreeding Diabetes Resistant (BBDR) and LEW1.WR1 rats have been used to decipher the mechanisms that lead to virus-induced T1D. Both animals develop β-cell inflammation and hyperglycemia upon infection with the parvovirus Kilham Rat Virus (KRV). Our earlier in vitro and in vivo studies indicated that KRV-induced innate immune upregulation early in the disease course plays a causal role in triggering β-cell inflammation and destruction. Furthermore, we recently found for the first time that infection with KRV induces inflammation in visceral adipose tissue (VAT) detectable as early as day 1 post-infection prior to insulitis and hyperglycemia. The proinflammatory response in VAT is associated with macrophage recruitment, proinflammatory cytokine and chemokine upregulation, endoplasmic reticulum (ER) and oxidative stress responses, apoptosis, and downregulation of adipokines and molecules that mediate insulin signaling. Downregulation of inflammation suppresses VAT inflammation and T1D development. These observations are strikingly reminiscent of data from obesity and type 2 diabetes (T2D) in which VAT inflammation is believed to play a causal role in disease mechanisms. We propose that VAT inflammation and dysfunction may be linked with the mechanism of T1D progression.

Transcriptional regulation of Treg homeostasis and functional specification

CD4+Foxp3+ regulatory T (Treg) cells are key players in keeping excessive inflammation in check. Mounting evidence has shown that Treg cells exert much more diverse functions in both immunological and non-immunological processes. The development, maintenance and functional specification of Treg cells are regulated by multilayered factors, including antigens and TCR signaling, cytokines, epigenetic modifiers and transcription factors (TFs). In the review, we will focus on TFs by summarizing their unique and redundant roles in Treg cells under physiological and pathophysiological conditions. We will also discuss the recent advances of Treg trajectories between lymphoid organs and non-lymphoid tissues. This review will provide an updated view of the newly identified TFs and new functions of known TFs in Treg biology.

Memory CD4+ T Cells in Immunity and Autoimmune Diseases

CD4⁺ T helper (Th) cells play central roles in immunity in health and disease. While much is known about the effector function of Th cells in combating pathogens and promoting autoimmune diseases, the roles and biology of memory CD4⁺ Th cells are complex and less well understood. In human autoimmune diseases such as multiple sclerosis (MS), there is a critical need to better understand the function and biology of memory T cells. In this review article we summarize current concepts in the field of CD4⁺ T cell memory, including natural history, developmental pathways, subsets, and functions. Furthermore, we discuss advancements in the field of the newly-described CD4⁺ tissue-resident memory T cells and of CD4⁺ memory T cells in autoimmune diseases, two major areas of important unresolved questions in need of answering to advance new vaccine design and development of novel treatments for CD4⁺ T cell-mediated autoimmune diseases.

Rat Models of Human Type 1 Diabetes

Rat models of human type 1 diabetes have been shown to be of great importance for the elucidation of the mechanisms underlying the development of autoimmune diabetes. The three major well-established spontaneous rat models are the BioBreeding (BB) diabetes-prone rat, the Komeda diabetes-prone (KDP) rat, and the IDDM (LEW.1AR1-iddm) rat. Their distinctive features are described with special reference to their pathology, immunology, and genetics and compared with the situation in patients with type 1 diabetes mellitus. For all three established rat models, a distinctive genetic mutation has been identified that is responsible for the manifestation of the diabetic syndrome in these rat strains.

Regulatory T cells: history and perspective

Despite the skepticism that once prevailed among immunologists, it is now widely accepted that the normal immune system harbors a T-cell population, called regulatory T cells (Treg cells), specialized for immune suppression. It was first shown that depletion of a T-cell subpopulation from normal rodents produced autoimmune disease. Search for a molecular marker specific for such autoimmune-preventive Treg cells has revealed that the majority, if not all, of them constitutively express the CD25 molecule as depletion of CD25(+)CD4(+) T cells spontaneously evokes autoimmune disease in otherwise normal rodents. The expression of CD25 by Treg cells has made it possible to delineate their developmental pathways, in particular their thymic development, and establish simple in vitro assay for assessing their suppressive activity. The marker and the in vitro assay have helped to identify human Treg cells with similar functional and phenotypic characteristics. Recent efforts have shown that natural Treg cells specifically express the transcription factor Foxp3 and that mutations of the Foxp3 gene produce a variety of immunological diseases in humans and rodents. Specific expression of Foxp3 in natural Treg cells has enabled their functional and developmental characterization by genetic approach. These studies altogether have provided firm evidence for Foxp3(+)CD25(+)CD4(+) Treg cells as an indispensable cellular constituent of the normal immune system for establishing and maintaining immunologic self-tolerance and immune homeostasis. Treg cells are now within the scope of clinical use to treat immunological diseases and control physiological and pathological immune responses.

Toll-like receptors and type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease that results in the progressive loss of insulin producing cells. Studies performed in humans with T1D and animal models of the disease over the past two decades have suggested a key role for the adaptive immune system in disease mechanisms. The role of the innate immune system in triggering T1D was shown only recently. Research in this area was greatly facilitated by the discovery of toll-like receptors (TLRs) that were found to be a key component of the innate immune system that detect microbial infections and initiate antimicrobial host defense responses. New data indicate that in some situations, the innate immune system is associated with mechanisms triggering autoimmune diabetes. In fact, studies preformed in the BioBreeding Diabetes Resistant (BBDR) and LEW1.WR1 rat models of T1D demonstrate that virus infection leads to islet destruction via mechanisms that may involve TLR9-induced innate immune system activation. Data from these studies also show that TLR upregulation can synergize with virus infection to dramatically increase disease penetrance. Reports from murine models of T1D implicate both MyD88-dependent and MyD88-independent pathways in the course of disease. The new knowledge about the role of innate immune pathways in triggering islet destruction could lead to the discovery of new molecules that may be targeted for disease prevention.

Regulatory T Cells in Immunologic Self-Tolerance and Autoimmune Disease

Naturally arising CD25+ CD4+ regulatory T cells play key roles in the maintenance of immunologic self-tolerance and negative control of various immune responses. The majority, if not all, of them are produced by the normal thymus as a functionally distinct T-cell subpopulation, and their generation is in part developmentally controlled. Genetic abnormality in the development and function of this population can indeed be a cause of autoimmune disease, immunopathology, and allergy in humans. This regulatory population can be exploited to prevent and treat autoimmune disease by strengthening and reestablishing immunologic self-tolerance.

Prevention of spontaneous immune-mediated diabetes development in the LEW.1AR1-iddm rat by selective CD8+ T cell transfer is associated with a cytokine shift in the pancreas-draining lymph nodes

AIMS/HYPOTHESIS

The LEW.1AR1-iddm rat is an animal model of spontaneous type 1 diabetes mellitus. This study analysed how adoptive transfer of selective T cell subpopulations affects the incidence of diabetes.

METHODS

CD4(+) or CD8(+) T cells were isolated from diabetic LEW.1AR1-iddm rats or diabetes-resistant LEW.1AR1 rats. Cells were selectively transferred into athymic LEW.1AR1-Whn ( rnu ) or prediabetic LEW.1AR1-iddm rats. The animals were monitored for blood glucose, islet infiltration and immune cell composition of pancreas-draining lymph nodes.

RESULTS

After adoptive transfer of CD4(+) T cells from diabetic LEW.1AR1-iddm rats into athymic LEW.1AR1-Whn ( rnu ) rats, 50% of the recipients developed diabetes. Transfer of CD8(+) T cells failed to induce diabetes. Only 10% of the athymic recipients became diabetic after co-transfer of CD4(+) and CD8(+) T cells. Adoptive transfer of CD8(+) T cells from LEW.1AR1 or diabetic LEW.1AR1-iddm rats into prediabetic LEW.1AR1-iddm rats significantly reduced the incidence of diabetes. In protected normoglycaemic animals regulatory CD8(+)/CD25(+) and CD4(+)/CD25(+) T cell subpopulations that were also FOXP3-positive accumulated in the pancreas-draining lymph nodes. In this lymphatic organ, gene expression of anti-inflammatory cytokines was significantly higher than in diabetic rats.

CONCLUSIONS/INTERPRETATION

Our results show that adoptive transfer of CD4(+) but not CD8(+) T cells from diabetic LEW.1AR1-iddm rats induced diabetes development. Importantly, CD8(+) T cells from diabetic LEW.1AR1-iddm rats and diabetes-resistant LEW.1AR1 rats provided protection against beta cell destruction. The accumulation of regulatory T cells in the pancreas-draining lymph nodes from protected rats indicates that transferred CD8(+) T cells may have beneficial effects in the control of beta cell autoimmunity.

Regulatory T cells - a brief history and perspective

It is now widely accepted that the normal immune system harbors a regulatory T-cell population specialized for immune suppression. It was found initially that some CD4(+) T cells in normal animals were capable of suppressing autoimmunity. Characterization of this autoimmune-suppressive CD4(+) T cell population revealed that they constitutively expressed the CD25 molecule, which made it possible to distinguish them from other T cells, delineate their developmental pathways, in particular their thymic development, and characterize their potent in vivo and in vitro immunosuppressive activity. The marker also helped to identify human regulatory T cells with similar functional and phenotypic characteristics. Recent studies have shown that CD25(+)CD4(+) regulatory T cells specifically express the transcription factor Foxp3. Genetic anomaly of Foxp3 causes autoimmune and inflammatory disease in rodents and humans through affecting the development and function of CD25(+)CD4(+) regulatory T cells. These findings at the cellular and molecular levels altogether provide firm evidence for Foxp3(+)CD25(+)CD4(+) regulatory T cells as an indispensable cellular constituent of the normal immune system and for their crucial roles in establishing and maintaining immunologic self-tolerance and immune homeostasis. They can be exploited for clinical use to treat immunological diseases and control physiological and pathological immune responses.

Naturally arising Foxp3-expressing CD25+CD4+ regulatory T cells in self-tolerance and autoimmune disease

Naturally arising CD25+CD4+ regulatory T cells, which express the transcription factor Foxp3, play key roles in the maintenance of immunologic self-tolerance and negative control of a variety of physiological and pathological immune responses. The majority of them are produced by the normal thymus as a functionally mature T cell subpopulation specialized for suppressive function. Their generation is in part genetically and developmentally controlled. Genetically determined or environmentally induced abnormality in CD25+CD4+ regulatory T cell development, maintenance, and function can be a cause of autoimmune disease in humans.

Effects of polyinosinic-polycytidylic acid and adoptive transfer of immune cells in the Lew.1AR1-iddm rat and in its coisogenic LEW.1AR1 background strain

The importance of the cellular immune system for the development of T1DM in the LEW.1AR1-iddm rat was investigated by use of polyinosinic-polycytidylic acid (Poly I:C) and by adoptive transfer of concanavalin A (Con A) activated lymphocytes from diabetic LEW.1AR1-iddm rats and the coisogenic LEW.AR1 background strain. Poly I:C treatment induced diabetes, characterized morphologically by a diffuse infiltration of the pancreas, in up to 20% of the animals of the coisogenic LEW.1AR1 background strain. It did not increase the diabetes incidence of 30% of the LEW.1AR1-iddm strain. In contrast Poly I:C treatment induced diabetes in up to 80% of the animals of the Mhc congenic LEW.1WR1 strain. Adoptive transfer of lymphocytes activated by the T-cell mitogen Con A from diabetic donors doubled the incidence of diabetes, characterized morphologically by a focal insulitis, in diabetes prone LEW.1AR1-iddm recipients. In contrast, animals of the LEW.1AR1 background strain did not develop diabetes after adoptive transfer. Moreover, adoptive transfer of Con A activated lymphocytes from LEW.1AR1 rats to LEW.1AR1-iddm rats with 30 or 60% diabetes incidence, significantly decreased the incidence of diabetes in LEW.1AR1-iddm rats with 60% diabetes incidence. The results show that autoreactive lymphocytes induce beta cell destruction in the LEW.1AR1-iddm rat, while the LEW.AR1 background strain apparently contains regulatory potential, which is able to counteract the autoimmune response.

Identifying Foxp3-expressing suppressor T cells with a bicistronic reporter

Regulatory T cells are critical for maintaining self-tolerance and to negatively regulate immune responses. Foxp3 is a regulatory T cell-specific transcription factor that functions as the master regulator of the development and function of regulatory T cells. Here, we report the generation of a mouse model, in which a bicistronic reporter expressing a red fluorescent protein has been knocked into the endogenous Foxp3 locus. Using this mouse model, we assessed Foxp3 expression in various lymphocyte compartments and identified previously unreported Foxp3-expressing cells. In addition, we showed that de novo Foxp3 expression along with suppressive function were induced by TGF-beta in activated CD4 T cells in vitro. Finally, we demonstrated that non-Foxp3-expressing CD4 T cells could not be converted into Foxp3-expressing cells upon adoptive transfer into immunodeficient hosts. This Foxp3 bicistronic reporter knockin mouse model should greatly enhance the study of regulation and function of Foxp3-expressing regulatory T cells.

Naturally arising Foxp3-expressing CD25+CD4+ regulatory T cells in immunological tolerance to self and non-self

Naturally arising CD25(+)CD4(+) regulatory T cells actively maintain immunological self-tolerance. Deficiency in or dysfunction of these cells can be a cause of autoimmune disease. A reduction in their number or function can also elicit tumor immunity, whereas their antigen-specific population expansion can establish transplantation tolerance. They are therefore a good target for designing ways to induce or abrogate immunological tolerance to self and non-self antigens.

Inflammatory bowel disease: dysfunction of GALT and gut bacterial flora (I)

Gut-associated lymphoid tissue (GALT) is the largest lymphoid organ in the body. This is not surprising considering the huge load of antigens (Ags) from food and commensal bacteria with which it interacts on a daily basis. Gut-associated lymphoid tissue has to recognise and allow the transfer of beneficial Ags whilst concurrently dealing with and successfully removing putative and overtly harmful Ags. This distinctive biological feature of GALT is believed to be crucial to good health. Deregulation or dysfunction of GALT is thought to predispose to inflammatory bowel diseases (IBD) such as ulcerative colitis and Crohn's disease. The exact mechanism(s) underlying the pathogenesis of IBD is (are) poorly understood and the immunological defects in GALT are poorly documented. Advances in immunology have highlighted the importance of dendritic cells (DCs), which are the key Ag presenting cells in tissues and lymphoid compartments. Their crucial role in GALT, in health and disease is discussed in this review. Interaction of DCs with T cells in the gut produces a subset of T lymphocytes, which have immunosuppressive function. Inappropriate Ag uptake and presentation to naïve T cells in mesenteric lymph nodes may lead to T cell tolerance in GALT. These various complex factors in the gut are discussed and their possible relevance to IBD evaluated.

A co-transfer system in young prediabetic BB rats: reactivated autoreactive T cells can be partly controlled

A transfer model for studying both the development and prevention of diabetes in rats is described in detail. Diabetes was induced in BBDR rats by combining RT6-depletion with PolyI:C treatment. Autoreactive cells were isolated from acutely diabetic donors, reactivated in vitro and transferred intravenously into young (<34-day-old) BBDP rats. Accelerated diabetes occurred 13+/-3 days or 18+/-4 days after transfer of reactivated splenocytes or purified T cells (42/43 or 26/27 recipients, respectively). Freshly isolated mesenteric and splenic leukocytes from adult, healthy BBDR rats prevented spontaneous diabetes in BBDP rats, but were not able to prevent the accelerated diabetes when co-transferred with the autoreactive cells. By contrast, diabetes was significantly delayed (P<0.001) when protective cells were transferred 4 days prior to the autoreactive cells (16+/-3 days). In vivo tracking studies of the two types of transferred cells suggest different homing patterns which may explain this finding. The data suggest that leukocytes from BBDR contain cells with the ability to regulate reactivated autoreactive T cells in an autoimmune environment. This in vivo model of recurrent diabetes can therefore be used to define which type of cells are most effective in suppressing established autoimmune destruction of beta-cells.

Naturally arising CD4+ regulatory t cells for immunologic self-tolerance and negative control of immune responses

Naturally occurring CD4+ regulatory T cells, the majority of which express CD25, are engaged in dominant control of self-reactive T cells, contributing to the maintenance of immunologic self-tolerance. Their depletion or functional alteration leads to the development of autoimmune disease in otherwise normal animals. The majority, if not all, of such CD25+CD4+ regulatory T cells are produced by the normal thymus as a functionally distinct and mature subpopulation of T cells. Their repertoire of antigen specificities is as broad as that of naive T cells, and they are capable of recognizing both self and nonself antigens, thus enabling them to control various immune responses. In addition to antigen recognition, signals through various accessory molecules and via cytokines control their activation, expansion, and survival, and tune their suppressive activity. Furthermore, the generation of CD25+CD4+ regulatory T cells in the immune system is at least in part developmentally and genetically controlled. Genetic defects that primarily affect their development or function can indeed be a primary cause of autoimmune and other inflammatory disorders in humans. Based on recent advances in our understanding of the cellular and molecular basis of this T cell-mediated immune regulation, this review discusses how naturally arising CD25+CD4+ regulatory T cells contribute to the maintenance of immunologic self-tolerance and negative control of various immune responses, and how they can be exploited to prevent and treat autoimmune disease, allergy, cancer, and chronic infection, or establish donor-specific transplantation tolerance.

Macrophages from high-risk HLA-DQB1*0201/*0302 type 1 diabetes mellitus patients are hypersensitive to lipopolysaccharide stimulation

Levels of nonantigen-induced pro-inflammatory cytokines and prostaglandin in macrophages isolated from human leucocyte antigen (HLA)-matched type 1 diabetes mellitus patients, first-degree relatives and healthy controls were determined. We hypothesize that monocytes isolated from patients are sensitized or preactivated and therefore, have an altered response to in vitro stimulus compared with control groups as measured by levels of pro- and anti-inflammatory mediators. In this study, peripheral blood monocytes were differentiated to macrophages with macrophage-colony stimulating factor (M-CSF) to determine lipopolysaccharide (LPS)-stimulated tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, IL-12 and prostaglandin E-2 (PGE-2) secretion from hetero- or homozygous HLA DQB1*0201 and *0302 type 1 diabetes mellitus patients, first-degree relatives and homozygous HLA DQB1*0602 healthy controls. LPS-stimulated secretion of TNF-alpha, IL-1beta and IL-6 was immediate and markedly higher in the HLA-DQB1*0201/*0302 type 1 diabetes patients compared with all other groups including HLA-matched healthy first-degree relatives. In DQB1*0201/*0302 diabetes patients PGE-2 secretion was delayed but increased by LPS stimulation compared with HLA-matched healthy relatives. IL-12 was not detected at any condition. These data suggest that macrophages from DQB1*0201/*0302 type 1 diabetes patients are sensitized to secrete both cytokines and PGE-2 following nonantigenic stimulation. Sensitized macrophages may be important to high-risk DQB1*0201/*0302-associated type 1 diabetes.

Antithyrotropin receptor antibody: an update

Numerous studies have reported the characteristics and significance concerning antithyrotropin receptor antibodies (TSHR-Abs), which cause Graves' disease and in some cases primary hypothyroidism. However, many unsolved questions concerning those antibodies remain. Here, recent developments in the study of TSHR-Abs are reviewed based on three aspects: mechanisms of TSHR-Ab production, antibody binding epitopes, and clinical TSHR-Ab assays. Mechanisms of TSHR-Ab production are discussed from five points of view: aberrant expression of the major histocompatibility complex, dysregulation of T cells, molecular mimicry, bystander effect, and expansion of autoreactive B cells. Regarding epitopes, unique TSHR-Abs have been reported that may explain the complicated pathophysiology of patients with TSHR-Ab diseases. Finally, recent efforts to improve TSHR-Ab measurements are introduced. Such efforts will contribute to clinical examinations and treatments for thyroid diseases as well as experimental methods of thyroidology.

Immunologic self tolerance maintained by T-cell-mediated control of self-reactive T cells: implications for autoimmunity and tumor immunity

T-cell-mediated dominant control of self-reactive T cells is one mechanism for maintaining immunologic self tolerance. It also hampers the generation of immunity to autologous tumor cells. Abrogation of the control can evoke potent tumor immunity as well as autoimmunity in normal animals. This common regulatory mechanism for autoimmunity and tumor immunity can be exploited to devise a novel immunotherapy against cancer.

BB rat thymocytes cultured in the presence of islets lose their ability to transfer autoimmune diabetes

Thymocytes from adult BB rats can adoptively transfer autoimmune diabetes to athymic recipients. It is also known that the development of BB rat T-cells is recapitulated in adult thymus organ cultures (ATOCs). Based on these observations, we tested the hypothesis that cells capable of the adoptive transfer of diabetes would be present in long-term ATOCs but could be rendered nondiabetogenic by co-culture with appropriate antigens. We observed that cells recovered from adult diabetes-resistant BB (BBDR) rat thymi cultured for up to 14 days can adoptively transfer disease to athymic WAG-rnu/rnu rats treated with polyinosinic: polycytidylic acid and a monoclonal antibody to preclude development of ART2a+ regulatory T-cells. Co-culture of adult BBDR thymi in the presence of BBDR thyrocytes had no effect on the ability of recovered cells to induce diabetes in 70-80% of adoptive recipients. In contrast, co-culture in the presence of islets prevented transfer of diabetes, on average, in >90% of recipients. Fresh islets, frozen islets, and islets pretreated with streptozotocin to deplete insulin were equally effective in preventing diabetes, but none prevented insulitis in nondiabetic recipients. Co-culture in the presence of islets was not associated with detectable alterations in phenotype or in the secretion of gamma-interferon or interleukin-4, either in cultures or in cells recovered from adoptive recipients. We conclude that islet antigens involved in the initiation of autoimmune diabetes in BB rats may be absent or deficient in BB rat thymi. Exposure of ATOCs to exogenous islets may lead to deletion or anergy of diabetogenic T-cells or to the positive selection of regulatory T-cells.

Levels of Art2+ cells but not soluble Art2 protein correlate with expression of autoimmune diabetes in the BB rat

ART2a and ART2b are isoenzymes expressed on the surface of mature T cells and intraepithelial lymphocytes (IELs) in the rat. They exhibit both adenosine diphosphoribosyltransferase and nicotine adenine dinucleotide (NAD) glycohydrolase activities, and both can generate a transmembrane signal that modulates T cell activation. The presence or absence of ART2+ T cells modulates the expression of autoimmune diabetes in the BB rat. ART2 also circulates in a soluble form whose function is unknown. We tested the hypothesis that circulating ART2 protein regulates the expression of autoimmunity. We compared the kinetics, regulation, and source of soluble ART2 in normal rats and in rats with autoimmune diabetes. Basal levels of soluble ART2 varied greatly among strains of rats and were lowest in the diabetes-prone BB (BBDP/Wor) rat. In diabetes-resistant BB (BBDR/Wor) rats, administration of anti-ART2a antibody, which is known to induce diabetes, resulted in transient clearing of soluble ART2a that was followed rapidly by a rebound increase. Repeated treatment of BBDR/Wor rats with anti-ART2a antibody resulted in sustained supraphysiologic levels of soluble ART2a. Although the number of peripheral ART2a+ T cells is known to correlate with the expression of diabetes in BBDR/Wor rats, the level of soluble ART2a protein did not. The source of the soluble ART2 protein in the rat appeared to be the gut. The results suggest that ART2+ T cells and soluble ART2 protein may subserve different immunomodulatory functions.

Naturally anergic and suppressive CD25(+)CD4(+) T cells as a functionally and phenotypically distinct immunoregulatory T cell subpopulation

A CD4(+) T cell subpopulation defined by the expression levels of a particular cell surface molecule (e.g. CD5, CD45RB, CD25, CD62L or CD38) bears an autoimmune-preventive activity in various animal models. Here we show that the expression of CD25 is highly specific, when compared with other molecules, in delineating the autoimmune-preventive immunoregulatory CD4(+) T cell population. Furthermore, although CD25 is an activation marker for T cells, the following findings indicate that immunoregulatory CD25(+)CD4(+) T cells are functionally distinct from activated or anergy-induced T cells derived from CD25(-)CD4(+) T cells. First, the former are autoimmune-preventive in vivo, naturally unresponsive (anergic) to TCR stimulation in vitro and, upon TCR stimulation, able to suppress the activation/proliferation of other T cells, whereas the latter scarcely exhibit the in vivo autoimmune-preventive activity or the in vitro suppressive activity. Second, such activated or anergy-induced CD25(-) spleen cells produce various autoimmune diseases when transferred to syngeneic athymic nude mice, whereas similarly treated normal spleen cells, which include CD25(+)CD4(+) T cells, do not. Third, upon polyclonal T cell stimulation, CD25(+)CD4(+) T cells express CD25 at higher levels and more persistently than CD25(-)CD4(+) T cell-derived activated T cells; moreover, when the stimulation is ceased, the former revert to the original levels of CD25 expression, whereas the latter lose the expression. These results collectively indicate that naturally anergic and suppressive CD25(+)CD4(+) T cells present in normal naive mice are functionally and phenotypically stable, distinct from other T cells, and play a key role in maintaining immunologic self-tolerance.

Induction of Tumor Immunity by Removing CD25+CD4+ T Cells: A Common Basis Between Tumor Immunity and Autoimmunity

This study shows that removal of a T cell subpopulation can evoke effective tumor immunity in otherwise nonresponding animals. Elimination of CD25-expressing T cells, which constitute 5–10% of peripheral CD4+ T cells in normal naive mice, elicited potent immune responses to syngeneic tumors in vivo and eradicated them. The responses were mediated by tumor-specific CD8+ CTLs and tumor-nonspecific CD4−8− cytotoxic cells akin to NK cells. Furthermore, in vitro culture of CD25+4+ T cell-depleted splenic cell suspensions prepared from tumor-unsensitized normal mice led to spontaneous generation of similar CD4−8− cytotoxic cells capable of killing a broad spectrum of tumors; reconstitution of CD25+4+ T cells inhibited the generation. In this culture, self-reactive CD25−4+ T cells responding to self peptides/class II MHC complexes on APCs spontaneously proliferated upon removal of CD25+4+ T cells, secreting large amounts of IL-2. The IL-2 thus produced appeared to be responsible for the generation of CD4−8− NK cells as lymphokine-activated killer cells, because direct addition of an equivalent amount of IL-2 to the culture of CD4−8− cells generated similar lymphokine-activated killer/NK cells, whereas coculture of normal CD4−8− cells with CD25−4+ T cells from IL-2-deficient mice did not. Thus, removal of immunoregulatory CD25+4+ T cells can abrogate immunological unresponsiveness to syngeneic tumors in vivo and in vitro, leading to spontaneous development of tumor-specific effector cells as well as tumor-nonspecific ones. This novel way of evoking tumor immunity would help to devise effective immunotherapy for cancer in humans.

The lymphopenia mutation of the BB rat causes inappropriate apoptosis of mature thymocytes

BB rats develop autoimmune diabetes mellitus at a high frequency. A key factor in the development of the disease is an autosomal recessive mutation determining peripheral T cell lymphocytopenia. Previous studies have suggested that the lymphopenia could be caused by increased cell death. Here we demonstrate that the lyp mutation dramatically reduces the in vitro lifespan of the TCRhi single-positive thymocytes and peripheral T cells, without abolishing their capacity to proliferate. The reduced lifespan is due to an increased rate of apoptosis, and is detected in single-positive thymocytes displaying characteristics of cells which have undergone positive selection. The cell death defect does not affect the in vitro lifespan of peripheral B cells. Interestingly, stimulation can rescue peripheral lyp/lyp T cells from immediate cell death. We propose that the lymphopenia mutation prevents the accumulation of a normal T cell pool, including regulatory subsets, without preventing the activation and proliferation of reactive T cells, thereby creating conditions appropriate for the development of uncontrolled autoimmune responses.

Thymus and Autoimmunity: Production of CD25+CD4+ Naturally Anergic and Suppressive T Cells as a Key Function of the Thymus in Maintaining Immunologic Self-Tolerance

This study shows that the normal thymus produces immunoregulatory CD25+4+8− thymocytes capable of controlling self-reactive T cells. Transfer of thymocyte suspensions depleted of CD25+4+8− thymocytes, which constitute ∼5% of steroid-resistant mature CD4+8− thymocytes in normal naive mice, produces various autoimmune diseases in syngeneic athymic nude mice. These CD25+4+8− thymocytes are nonproliferative (anergic) to TCR stimulation in vitro, but potently suppress the proliferation of other CD4+8− or CD4−8+ thymocytes; breakage of their anergic state in vitro by high doses of IL-2 or anti-CD28 Ab simultaneously abrogates their suppressive activity; and transfer of such suppression-abrogated thymocyte suspensions produces autoimmune disease in nude mice. These immunoregulatory CD25+4+8− thymocytes/T cells are functionally distinct from activated CD25+4+ T cells derived from CD25−4+ thymocytes/T cells in that the latter scarcely exhibits suppressive activity in vitro, although both CD25+4+ populations express a similar profile of cell surface markers. Furthermore, the CD25+4+8− thymocytes appear to acquire their anergic and suppressive property through the thymic selection process, since TCR transgenic mice develop similar anergic/suppressive CD25+4+8− thymocytes and CD25+4+ T cells that predominantly express TCRs utilizing endogenous α-chains, but RAG-2-deficient TCR transgenic mice do not. These results taken together indicate that anergic/suppressive CD25+4+8− thymocytes and peripheral T cells in normal naive mice may constitute a common T cell lineage functionally and developmentally distinct from other T cells, and that production of this unique immunoregulatory T cell population can be another key function of the thymus in maintaining immunologic self-tolerance.

From genome to aetiology in a multifactorial disease, type 1 diabetes

The common autoimmune disease type 1 diabetes provides a paradigm for the genetic analysis of multifactorial disease. Disease occurrence is attributable to the interaction with the environment of alleles at many loci interspersed throughout the genome. Their mapping and identification is difficult because the disease-associated alleles occur almost as commonly in patients as in healthy individuals; even the highest-risk genotypes bestow only modest risks of disease. The identification of common quantitative trait loci (QTL) in autoimmune disease and in other common disorders, therefore, requires a very close marriage of genetics and biology. Two QTLs have been identified in human type 1 diabetes: the major histocompatibility complex HLA class II loci and a promoter polymorphism of the insulin gene. The evidence for their primary roles in disease aetiology demonstrates the necessity of combined studies of genetics and biology. Their functions and interaction underpin an emerging picture of the basic causes of the disease and direct analyses towards other candidate genes and pathways. The genetic tools used for QTL identification include transgenesis and gene knockouts, whole genome scanning for linkage, mouse congenic strains, linkage disequilibrium mapping, and the establishment of ancestral haplotypes among disease-associated chromosomes.

Mono(ADP-ribosyl)transferases and related enzymes in animal tissues. Emerging gene families

Mono-ADP-ribosylation, like phosphorylation, is an enzyme-catalyzed, reversible post-translational modification that modulates protein function. It was originally discovered as the pathogenic principle of diphtheria-, cholera-, and other potent bacterial toxins. By analogy, corresponding enyzmes were postulated to exist in animal tissues, and mounting biochemical evidence indicates that such enzymes, indeed, play important regulatory roles in cellular functions. The molecular cloning of the first mammalian mono(ADP-ribosyl)transferase from rabbit skeletal muscle, the finding of its homology to a well-studied T-cell marker, RT6, and the molecular cloning of additional gene family members from mammals and birds is providing fresh impetus to research in this field. Intriguingly, these vertebrate enzymes are predicted to be secretory or membrane proteins. They are expressed in lymphatic tissues, muscle, testis, bone marrow, and erythroblasts. Here we review the relationship between this novel family of eucaryotic mono(ADP-ribosyl)transferases (mADPRTs), ADP-ribosylating bacterial toxins, the poly(ADP-ribose)polymerase (PARP), the ADP-ribosyl cyclases, and the ADP-ribosylprotein hydrolase (ARH) in terms of their structure, enzymatic properties and possible biological functions.

Histomorphological aspects of the development of thyroid autoimmune diseases: consequences for our understanding of endocrine ophthalmopathy

In this short review we will first evaluate the histomorphological aspects of the human and spontaneous animal thyroid autoimmune diseases. These diseases include Hashimoto goiter, primary myxedema, Graves' disease, and the spontaneous forms of thyroiditis in the Bio Breeding (BB) rat, the nonobese diabetic (NOD) mouse, and the obese strain (OS) of chicken. Based on sequential histomorphological events in the animal models of thyroid autoimmune disease, a mechanism for the pathogenesis of thyroid autoimmune disease is proposed. Since one of the human thyroid autoimmune diseases, specifically Graves' disease, is often associated with ophthalmopathy, the histomorphological aspects of the ophthalmopathic process are also evaluated to consider its possible autoimmune character.

Abnormalities in the export and fate of recent thymic emigrants in diabetes-prone BB/W rats

Abnormalities in postthymic T cell development in the BB/W rat model of autoimmune insulin-dependent diabetes mellitus (IDDM) result in part from a lymphopenia (lyp) gene defect. To better characterize these abnormalities, the phenotypes of T cells from diabetes-prone (DP) and diabetes-resistant (DR) coisogenic rats were analyzed by multiparameter flow immunocytometry (FCM). Marked decreases in the numbers of Thy1- RT6+ T cells, most of which are CD8+, were documented in DP rats by live-gating. Conversely, an approximately 3-fold increase was observed in the percentage of Thy1+ RT6- T cells, which normally serve as the precursors of both Thy1- RT6+ and Thy1- RT6- T cell subsets in rats. These results suggested that, at a minimum, an arrest in maturation of the Thy1+ precursors of RT6+ T cells occurs postthymically in DP rats. To determine more precisely the stage(s) in T cell development at which lymphopenia occurs, the export and fate of recent thymic emigrants (RTE's) and their immediate descendants in DP rats was traced after intrathymic (i.t.) labelling with fluorescein isothiocyanate (FITC). The results showed that in DP, as compared with DR, rats: 1) 5-fold fewer RTE's are exported from the thymus per 24 hr; 2) more than 80% of the RTE's are CD4+; 3) most of the immediate descendants of RTE's disappear from the peripheral lymphoid tissues within one week after export from the thymus; and 4) few of the descendants of the RTE's that do survive differentiate into RT6+ T cells. Staining with propidium iodide revealed that a significantly higher proportion of Thy1+ T cells in DP than in DR rats are in cycle (S/G2/M), thereby accounting for their disproportionately high numbers relative to RTE's. These results indicate that, in addition to defective thymic export, most of the immediate descendants of RTE's in DP rats undergo non-productive proliferation and death at the time (3-7 days postthymic) at which their counterparts in DR rats differentiate into Thy1- RT6+ T cells. The resulting deficiency of immunoregulatory T cells, acting in concert with defective intrathymic selection of effector T cell precursors, appears to conspire to markedly enhance the predisposition of DP rats to autoimmunity.

A major histocompatibility complex class II restriction for BioBreeding/Worcester diabetes-inducing T cells

Inbred diabetes-prone (DP) BioBreeding/Worcester (BB/Wor) (RT1u) rats develop spontaneous autoimmune diabetes, which, like human insulin-dependent diabetes mellitus, is mediated by autoreactive T lymphocytes. Breeding studies have shown an absolute requirement for at least one copy of the major histocompatibility complex (MHC) RT1u haplotype for spontaneous diabetes expression. Concanavalin A-activated spleen cells from acutely diabetic DP rats adoptively transfer diabetes only to recipients that express at least one RT1u haplotype. To investigate the basis for the MHC requirement in BB/Wor autoimmunity, diabetes-inducing T cell lines were derived from the spleens of acutely diabetic DP rats. Upon activation in vitro with islet cells, the T cell lines adoptively transfer insulitis and diabetes into young DP recipients and non-diabetes-prone RT1 congenic rat strains that are class IIu. Recipients that are RT1u at only the class I A or C locus, but not at the class II B/D loci, do not develop diabetes after T cell transfer. The adoptive transfer of diabetes by Concanavalin A-activated diabetic DP spleen cells also requires that donor and recipient share class II B/Du gene products. Furthermore, the adoptive transfer of diabetes into MHC class IIu congenic rats is independent of the class I haplotype; i.e., it occurs in the presence of class I Aa Cu or Au Ca gene products. BB/Wor T cells can be activated in vitro for the transfer of diabetes with islet cell antigens and class II-positive but not class IIu-negative antigen-presenting cells. The inductive phase of BB diabetes is therefore MHC class II restricted, and this appears to operate at the level of interaction between inducing T cells and class IIu antigen-presenting cells. These results may explain the well-documented, but not yet understood, MHC class II genetic contribution to insulin-dependent diabetes mellitus pathogenesis, and they may facilitate the development of protocols designed to prevent diabetes onset in susceptible individuals.

T cells from BB-DP rats show a unique cytokine mRNA profile associated with the IDDM1 susceptibility gene, Lyp

Diabetes prone biobreeding rats display several abnormalities in T cell numbers, T cell function and T cell surface phenotype which are associated with the onset of spontaneous disease. One of the most pronounced abnormalities in these animals is a marked T cell lymphopenia which is evident in both CD4+ and CD8+ peripheral T cell subsets. To gain a better understanding as to the nature of T cell responses in these animals, we have utilized RT-PCR to analyze the cytokine mRNA profiles of mitogen activated peripheral T cells derived from lymphopenic and non-lymphopenic animals. Our results suggest that inheritance of the lymphopenia gene, Lyp, is associated with a unique cytokine profile most similar to that previously described for mouse medullary thymocytes. In addition, cell surface staining of peripheral T cells from diabetes prone animals revealed a high frequency of Thyl+ cells, which is characteristic of both thymocytes and recent thymic emigrants. Following thymectomy, T cell responsiveness to a number of different stimuli is greatly reduced on a cell for cell basis as is the absolute number of surviving T cells. Taken collectively, our results suggest that the majority of the peripheral T cell pool in these diabetic prone rats consists of short lived, recent thymic emigrants which most likely also contain the effector cells required for initiation of diabetes.

Thyroglobulin-reactive T lymphocytes in thyroiditis-prone BB/Wor rats

Autoimmune lymphocytic thyroiditis (LT) is a common cause of primary hypothyroidism. Autoreactive T lymphocytes are clearly associated with this disorder, but their pathogenic role in spontaneously occurring LT remains to be established. In the present study, thyroglobulin-reactive T lymphocytes were cultured from young, unprimed LT-prone BB/Wor rats before the age of spontaneously-occurring LT. Although similar investigations have been conducted in animal models for experimental autoimmune thyroiditis (EAT), this study is unique because it examines a mammalian model for spontaneous LT. Splenic T lymphocytes were isolated from unprimed 30 to 45-day-old Fisher and LT-prone BB/Wor rats before the onset of LT, then tested for activation by normal (NL), iodine-poor (LI), and iodine-rich (HI) rat thyroglobulin (Tg) in bulk proliferation assay. BB/Wor rat lymphocytes were activated by all three Tg preparations, but Fisher lymphocytes were unresponsive (BB/Wor vs Fisher; p < 0.0001, Student's t-test). There was no difference between BB/Wor rat responses to the three preparations (p > 0.05, ANOVA). Based on these results, we conclude that Tg-responsive T lymphocytes can be cultured from young, unprimed LT-prone BB/Wor rats. Isolating such lymphocytes before the onset of histologically demonstrable LT strengthens the argument that antigen-specific T cells have a pathogenic role in the development of spontaneous autoimmune thyroid disease. The fact that these lymphocytes recognized normal, iodine-rich and iodine poor preparations of rat Tg equally well suggest that unlike the EAT model, spontaneously-occurring Tg-reactive T cells are not influenced by thyroglobulin's iodine content.

Role of RT6+ T lymphocytes in mercury-induced renal autoimmunity: experimental manipulations of "susceptible" and "resistant" rats

Brown Norway (BN) rats, "susceptible" to the autoimmune effects of mercury, experience a decrease of peripheral RT6.2+ T lymphocytes after the injection of relatively low doses of mercuric chloride. This change coincides with the appearance of circulating autoantibodies to renal antigens (e.g., laminin). Lewis (LEW) rats, "resistant" to the autoimmune effects of mercury, do not show significant decreases of RT6+ T cells. It is possible that BN rats are particularly sensitive to stress induced by mercury and that secretion of adrenocortical hormones decreases levels of RT6+ T cells in this rat strain. Alternatively, mercury may induce a graft-versus-host-like syndrome in BN rats, resulting in higher levels of corticosteroids capable of affecting RT6+ lymphocytes. To eliminate the possible influence of adrenocortical hormones, we have adrenalectomized BN rats prior to administration of mercury. Autoimmune responses to renal antigens were not affected by this experimental manipulation. Similarly, adrenalectomized rats exposed to mercury showed a significant decrease of RT6+ T lymphocytes in cervical lymph nodes. Overall, these observations do not support the hypothesis that increases in adrenocortical hormones play a major role in mercury-induced changes of RT6+ T cells. We have also explored whether experimental depletion of RT6+ T lymphocytes would result in autoimmunity. Gamma irradiation of BN rats led to a decrease of RT6+ T splenocytes, but by itself (i.e., without exposure to mercury) did not cause autoimmune responses to renal antigens. In addition, gamma-irradiated BN rats treated with mercury had autoimmune responses similar to those observed in mercury-treated nonirradiated controls. Depletion of RT6+ T cells in LEW rats through the use of a monoclonal antibody against the RT6.1 alloantigen did not by itself cause renal autoimmunity in this "resistant" strain. Depletion followed by administration of mercury also failed to induce renal autoimmunity. The lack of autoimmune effects in RT6-depleted BN and LEW rats suggests that a combination of several factors may be necessary to break self-tolerance and cause mercury-induced autoimmunity. Such factors likely comprise both environmental (mercury) and endogenous, genetically determined components. The latter include regulatory T cells (possibly RT6+), major histocompatibility complex (MHC), and T-cell receptors (TCR). Thus, BN rats with decreased percentages of immunoregulatory RT6+ T lymphocytes require additional immunotoxic and/or toxic effects of mercury for autoimmunity to occur. On the other hand, LEW rats depleted of regulatory T cells may still be unable to develop renal autoimmunity after exposure to mercury because they lack the appropriate MHC and TCR.

CD4+ T cells that express high levels of CD45RB induce wasting disease when transferred into congenic severe combined immunodeficient mice. Disease development is prevented by cotransfer of purified CD4+ T cells

Purified CD4+ lymph node T cells were sorted into two populations on the basis of their expression of CD45RB (CD45RBhi and CD45RBlo) and injected into congenic severe combined immunodeficient (SCID) mice. After a period of time that was dependent on the number of cells injected, the SCID mice that received CD45RBhi/CD4+ T cells developed a wasting disease that was not seen in SCID mice that received the CD4+/CD45RBlo cells or whole lymph node cells. At death, SCID mice that received the CD4+/CD45RBhi cells had increased spleen and lymph node cellularity compared with normal SCID mice and SCID mice that received the CD4+/CD45RBlo T cells. The spleen and lymph node contained CD4+ cells and neither CD8+ nor surface immunoglobulin M-positive cells, plus a population of cells that did not express any of those markers. At necropsy, the SCID mice that received the CD4+/CD45RBhi cells had significant hyperplasia of the intestinal mucosa with significant lymphoid cell accumulation in the lamina propria. Interestingly, mice that received mixtures of whole lymph node or purified CD4+ cells with CD4+/CD45RBhi cells did not develop weight loss, indicating that the unseparated CD4+ population contained cells that were capable of regulating the reactivity of the CD4+/CD45RBhi cells.

Autoimmune polyendocrine failure--type 1 (insulin-dependent) diabetes mellitus and hypothyroidism--after allogeneic bone marrow transplantation in a patient with lymphoblastic leukaemia

In this report we describe a patient who, after allogeneic bone marrow transplantation from her HLA-identical sister, developed polyendocrine failure in the form of Type 1 (insulin-dependent) diabetes mellitus and hypothyroidism. This was the result of the transfer of donor lymphoid cells which were activated by allogeneic bone marrow transplantation. The full chimerism of the recipient was demonstrated by restriction fragment length polymorphism analysis from nucleated blood cells and fibroblast DNA. During the 9-year follow-up, the donor developed hypothyroidism and signs of pre-Type 1 diabetes. This clinical observation resembles the adoptive transfer of diabetes observed in non-obese-diabetic mice and BB rats and confirms the role of immune processes in the pathogenesis of this disease.

Mercury-induced renal autoimmunity: changes in RT6+ T-lymphocytes of susceptible and resistant rats

The repeated administration of mercury to rats of the Brown Norway (BN) inbred strain results in a self-limiting production of autoantibodies to renal antigens (e.g., laminin) and autoimmune glomerulonephritis. In contrast, rats of the Lewis (LEW) strain do not develop renal autoimmunity after mercury treatment. Suppressor T-cells and/or the idiotype-anti-idiotype network have been implicated in the control of autoimmunity in susceptible (BN) rats as well as the "resistant" state of nonsusceptible (LEW) animals. In our investigations of the immune regulation of mercury-induced autoimmune glomerulonephritis, we have performed a phenotypic analysis of lymphocyte subpopulation in the spleens and lymph nodes of mercury-treated and control LEW, BN, and (BN x LEW) F1 hybrid rats. Of particular interest were RT6+ T-cells, a subpopulation of lymphocytes that may have immunoregulatory properties and show a relative decrease in mercury-treated BN rats concomitantly with the development of autoimmune responses to renal autoantigens. LEW rats did not develop renal autoimmunity after mercury treatment and had no significant change in the ratio of RT6+ to RT6- T-lymphocytes. Interestingly, the administration of mercury to (BN x LEW) F1 hybrid rats caused effects similar to those observed in the BN strain. Auto-immune responses to antigens of the kidney coincided with a change in the balance within the RT6 cell population, which was altered in favor of T-lymphocytes that do not express the RT6 phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of disease recurrence in diabetic BB/Pfd rats after syngeneic islet transplantation

Restimulation of autoreactivity in two different BB rat sublines of the same origin (Ottawa, Canada) was investigated by syngeneic islet transplantation into diabetic animals. Despite identical methods and conditions recurrence of hyperglycaemia was observed in BB/OK rats (Karlsburg, Germany) but not in BB/Pfd rats (Leuven, Belgium). Pancreatic morphology at the time of transplantation revealed significant differences in islet volume density and the degree of insulitis. Additionally, marked differences in the phenotypical composition of cells infiltrating the islets were observed. A loss of autoimmune memory in BB/Pfd rats is discussed as a probable reason for the lack of disease recurrence in those animals.

Causes and mechanism of autoimmune disease: cyclosporin A as a probe for the investigation

Organ-specific autoimmune disease can be elicited in rodents by manipulating the thymus/T cells. For example, elimination of a particular T-cell subset causes organ-specific autoimmune diseases, such as thyroiditis and gastritis, in otherwise normal mice. Environmental agents can cause similar autoimmune diseases by affecting the thymus/T cells. Cyclosporin A (CsA), a potent immunosuppressive drug, is an example. When a particular strain of newborn mice are daily administered with CsA for a limited period, they spontaneously develop organ-specific autoimmune disease, such as gastritis with anti-parietal cell autoantibodies, later in life. CsA abrogates the production of CD4+T cells and CD8+T cells in the thymus. Consequently, these T cells are substantially depleted from the peripheral lymphoid organs, especially when the drug is administered from the day of birth. The autoimmune disease is prevented when CsA-treated newborn mice are inoculated with splenic T cells from normal syngeneic adult mice. On the other hand, removal of the thymus immediately after neonatal CsA treatment produces autoimmune disease with a higher incidence and in a wider spectrum of organs, i.e., thyroiditis, sialoadenitis of the salivary gland, gastritis, insulitis of the endocrine pancreas, adrenalitis, oophoritis, or orchitis. Each autoimmune disease is accompanied by the development of circulating autoantibodies specific for the corresponding organ-specific antigens. These findings taken together indicate that CsA causes autoimmune disease not by affecting the target self-antigens, but by interfering with a thymus/T cell-dependent control mechanism on the production/expansion of pathogenic self-reactive T cells. Various other environmental insults (such as ionizing radiation or virus) can also cause similar autoimmune diseases, presumably by a similar mechanism.

Prevention of autoimmune diabetes in the BB rat by intrathymic islet transplantation at birth

Spontaneous diabetes in the BioBreeding (BB) rat, like human type I diabetes, results from the destruction of pancreatic islets by autoreactive T lymphocytes recognizing beta cell-specific antigens. T cell tolerance is in part mediated by interactions of maturing thymocytes with antigens expressed in the thymic microenvironment; islets were therefore implanted into the thymus of neonatal diabetes-prone BB rats to determine whether exposure of T cell precursors to beta cell antigens could influence the development of diabetes. This treatment completely prevented diabetes and insulitis in the native pancreas. The effect may be the result of specific modulation of diabetogenic T cells maturing in an islet-bearing thymus.