Autoimmune thyroiditis induced in mice depleted of particular T cell subsets. III. Analysis of regulatory cells suppressing the induction of thyroiditis

In Vitro Recapitulation of Murine Thymopoiesis from Single Hematopoietic Stem Cells

We report a serum-free, 3D murine artificial thymic organoid (M-ATO) system that mimics normal murine thymopoiesis with the production of all T cell stages, from early thymic progenitors to functional single-positive (CD8SP and CD4SP) TCRαβ and TCRγδ cells. RNA sequencing aligns M-ATO-derived populations with phenotypically identical primary thymocytes. M-ATOs initiated with Rag1^−/− marrow produce the same differentiation block as seen in the endogenous thymus, and Notch signaling patterns in M-ATOs mirror primary thymopoiesis. M-ATOs initiated with defined hematopoietic stem cells (HSCs) and lymphoid progenitors from marrow and thymus generate each of the downstream differentiation stages, allowing the kinetics of T cell differentiation to be tracked. Remarkably, single HSCs deposited into each M-ATO generate the complete trajectory of T cell differentiation, producing diverse TCR repertoires across clones that largely match endogenous thymus. M-ATOs represent a highly reproducible and efficient experimental platform for the interrogation of clonal thymopoiesis from HSCs.

Montel-Hagen et al. develop a murine artificial thymic organoid (M-ATO) system to reproduce thymopoiesis in vitro from bone marrow stem and progenitor cells (HSPCs). This method efficiently recapitulates the phenotypic and transcriptional features of normal murine T cell development even when initiated with a single HSC.

Hormones of thyroid gland in sera of rats treated with different dose of concentrated potassium iodine solutions

INTRODUCTION

Potassium iodine (KI) is used as a drug therapy for treating numerous diseases such as small-vessel vasculitis, erythema nodosum, vasculitis nodularis, Sweet's syndrome, tuberculosis and granulomatosis, and for iodized salt. At the same time, KI can be harmful. Iodine intake may increase the frequency of thyroiditis in humans, and may induce the occurrence of experimental thyroiditis (ET) in animals. Investigations on an experimental model for the examination of thyroiditis in Wistar rats have clearly showed morphological changes in the rat thyroid evoked by KI administration.

OBJECTIVE

The purpose of this study was to compare the effects of low and high doses of KI on the thyroid gland of Wistar rats and determine the effect on hormone status (T4, T3 and TSH) in this rat strain.

METHODS

Two groups of rats from the Wistar strain were treated with a low iodine dose (225 microg/g BW) and with a high iodine dose (675 microg/g BW) of KI solutions. Untreated nonimmunized animals served as controls. The solution was administrated daily intraperitoneally during the period of 26 consecutive days.

RESULTS

Monitoring hormone status (TSH, T3 and T4) and morphological changes it was found that therapeutic doses of KI applied in treatment induced the occurrence of experimental thyroiditis (chronic destructive Hashimoto's thyroiditis in humans) and cell necrosis in animals not carrying a genetic susceptibility. Significant inflammatory changes were observed in rats treated with a high iodine dose.

CONCLUSION

The early iodine induced cell necrosis and inflammation in the nonimmunized animals without genetic susceptibility is a new experimental model of thyroiditis.

Control of autoimmunity by naturally arising regulatory CD4+ T cells

Naturally acquired immunological self-tolerance is not entirely accounted for by clonal deletion, anergy, and ignorance. It is now well established that the T cell-repertoire of healthy individuals harbors self-reactive lymphocytes with a potential to cause autoimmune disease and these lymphocytes are under dominant control by a unique subpopulation of CD4+ T cells now called regulatory T cells. Efforts to delineate these Treg cells naturally present in normal individuals have revealed that they are enriched in the CD25+ CD4+ population. The identification of the CD25 molecule as a useful marker for naturally arising CD4+ regulatory T cells has made it possible to investigate many key aspects of their immunobiology, including their antigen specificities and the cellular/molecular pathways involved in their development and their mechanisms of action. Furthermore, reduction or dysfunction of the CD25+ CD4+ regulatory T cell population can be responsible for certain autoimmune diseases in humans.

T Cell Vaccination in Experimental Autoimmune Encephalomyelitis: A Mathematical Model

T cell vaccination (TCV) is a method to induce resistance to autoimmune diseases by priming the immune system with autoreactive T cells. This priming evokes an anti-idiotypic regulatory T cell response to the receptors on the autoreactive T cells. Hence resistance is induced. To prevent the inoculated autoreactive cells from inducing autoimmunity, cells are given in a subpathogenic dose or in an attenuated form. We developed a mathematical model to study how the interactions between autoreactive T cells, self epitopes, and regulatory cells can explain TCV. The model is based on detailed data on experimental autoimmune encephalomyelitis, but can be generalized to other autoimmune diseases. We show that all of the phenomena collectively described as TCV occur quite naturally in systems where autoreactive T cells can be controlled by anti-idiotypic regulatory T cells. The essential assumption that we make is that TCV generally involves self epitopes for which T cell tolerance is incomplete. The model predicts a qualitative difference between the two vaccination methods: vaccination with normal autoreactive cells should give rise to a steady state of long lasting protection, whereas vaccination with attenuated cells should only confer transient resistance. Moreover, the model shows how autoimmune relapses can occur naturally without the involvement of T cells arising due to determinant spreading.

Suppression of actively induced experimental autoimmune uveoretinitis by CD4+ T cells

BACKGROUND

Helper/inducer T cells that exert an inhibitory effect on disease induction have been recently found in many experimental models. In order to clarify the mechanisms of spontaneous remission of experimental autoimmune uveoretinitis (EAU), we investigated the inhibitory effect and the phenotype of the post-recovery suppressor cells.

METHODS

In a series of experiments, we separated spleen cells of rats that had recovered from EAU. Three groups of spleen cells, CD4+ T, CD8+ T and B cells, were each adoptively transferred into naive syngeneic rats before active immunization with retinal soluble antigen (S-Ag) and Freund's complete adjuvant or passive immunization with uveitogenic T cells from donor rats. Inflammation was examined clinically and histologically.

RESULTS

The development of EAU could be significantly prevented by adoptive transfer of CD4+ T cells, whereas CD8+ T cells could not suppress the onset. However, post-recovery CD4+ T cells failed to inhibit EAU induced by passive immunization with uveitogenic T cells.

CONCLUSION

These findings indicate that CD4+ post-recovery (suppressor) T cells may play an important role in the remission of EAU.

Inactivation of T cell receptor peptide-specific CD4 regulatory T cells induces chronic experimental autoimmune encephalomyelitis (EAE)

T cell receptor (TCR)-recognizing regulatory cells, induced after vaccination with self-reactive T cells or TCR peptides, have been shown to prevent autoimmunity. We have asked whether this regulation is involved in the maintenance of peripheral tolerance to myelin basic protein (MBP) in an autoimmune disease model, experimental autoimmune encephalomyelitis (EAE). Antigen-induced EAE in (SJL x B10.PL)F1 mice is transient in that most animals recover permanently from the disease. Most of the initial encephalitogenic T cells recognize MBP Ac1-9 and predominantly use the TCR V beta 8.2 gene segment. In mice recovering from MBP-induced EAE, regulatory CD4+ T cells (Treg) specific for a single immunodominant TCR peptide B5 (76-101) from framework region 3 of the V beta 8.2 chain, become primed. We have earlier shown that cloned B5-reactive Treg can specifically downregulate responses to Ac1-9 and also protect mice from EAE. These CD4 Treg clones predominantly use the TCR V beta 14 or V beta 3 gene segments. Here we have directly tested whether deletion/blocking of the Treg from the peripheral repertoire affects the spontaneous recovery from EAE. Treatment of F1 mice with appropriate V beta-specific monoclonal antibodies resulted in an increase in the severity and duration of the disease; even relapses were seen in one-third to one-half of the Treg-deleted mice. Interestingly, chronic disease in treated mice appears to be due to the presence of Ac1-9-specific T cells. Thus, once self-tolerance to MBP is broken by immunization with the antigen in strong adjuvant, TCR peptide-specific CD4 Treg cells participate in reestablishing peripheral tolerance. Thus, a failure to generate Treg may be implicated in chronic autoimmune conditions.

Fine T-cell subsets in alcoholics as determined by the expression of L-selectin, leukocyte common antigen, and beta-integrin

Alcoholics admitted to the hospital solely for detoxication have been studied by flow cytometry to evaluate changes in the surface markers of peripheral blood leukocytes. As we have shown previously, such patients have an elevated percentage of CD8hi lymphocytes that are HLA DR+; we now demonstrate that they also have striking alterations in the quantitative relationships of the fine T-cell subsets. Both CD4+ and CD8hi lymphocytes have a sharply reduced percentage of the L-selectin+ CD45RA+ subset, increased percentages of the CD45RA- subsets, and several other fine subset alterations. The fine subset profile suggests, according to current correlations of phenotype and function, that both CD4+ suppressor inducer and CD4-dependent CD8+ suppressor effector cells are reduced, whereas other subsets, including CD8+ CTL or their precursors, are increased in relative percentages. Some of the phenotypic changes are reversible over the several days following withdrawal. In other results, the percentage of CD8hi lymphocytes epxressing CD11b (beta-integrin) is shown to be reciprocal with the percentage expressing L-selectin both in normals and alcoholics. However, the regression function of CD11b vs. L-selectin on CD8hi cells is different for the alcoholics than for the normals, indicating an abnormality in the regulation of the expression of these two adhesion markers. Taken together, this abnormality of adhesion molecules and the fine subset alterations previously described indicate widespread changes in the peripheral lymphocytes of currently drinking alcoholics. These changes suggest functional deficiencies that may include alterations of lymphocyte traffic and other adhesion-dependent functions, and a shift in the balance of regulatory interactions.

Immunoregulation in autoimmune thyroid disease

We have postulated over many years that autoimmune thyroid diseases (AITD) are disorders of immunoregulation due to antigen specific defect(s) in suppressor (regulatory) T (Ts) lymphocyte function. Despite earlier skepticism, there is recent increased evidence to support this view. Several investigators working with animal models have demonstrated T lymphocyte subsets that are regulatory, i.e., will prevent AITD; conversely, depletion of these cells precipitates the lesion in the experimental models. These cells have been shown to be inadequately activated by specific antigen. In human AITD, recent studies have demonstrated that CD8+ (suppressor/cytotoxic) and CD8+CD11b+ ("pure suppressor") cells are activated by irrelevant antigen normally, but are significantly less well activated in response to thyroglobulin or thyroperoxidase. In further similar studies, CD8+ cells from patients with Graves' disease (GD) are induced normally in response to glutamic acid decarboxylase-65 (GAD-65), the putative beta cell antigen important in insulin-dependent diabetes mellitus (IDDM), but significantly less to synthetic TSH receptor (TSHR). Conversely, CD8+ cells from patients with IDDM are activated normally in response to TSHR, but significantly less to GAD-65. While these reductions in activation are partial only, and other additive factors playing on the immune system may be necessary to precipitate AITD, this disorder in the activation of Ts cells may be fundamental to the development of these disorders. This in turn may be due to molecular disturbances in MHC-related genes that dictate the mechanisms of presentation of specific antigen.

Thyroid hypofunction related with the progression of human immunodeficiency virus infection

Thyroid function was evaluated in 119 human immunodeficiency virus (HIV) infected patients at different stages of infection, compared with euthyroid normal subjects and hepatitis C virus infected blood donors as control groups. The low T3 state, well documented in severe nonthyroidal illnesses, was not found in these HIV infected patients. They showed lower FT4 levels and higher TSH and TBG values than euthyroid normal controls. These findings suggested a thyroid hypofunction becoming more evident with the progression of the infection as also supported by the presence of antithyroid autoantibodies mainly found in the symptomatic stages of the infection.

Evidence that the T cell repertoire of normal rats contains cells with the potential to cause diabetes. Characterization of the CD4+ T cell subset that inhibits this autoimmune potential

Diabetes was induced in a normal nonautoimmune rat strain by rendering the animals relatively T cell deficient using a protocol of adult thymectomy and sublethal gamma irradiation. All male rats and 70% of females developed an acute syndrome with severe loss of weight and hyperglycemia. Diabetes in these lymphopoenic rats was associated with extensive insulitis involving CD4+ and CD8+ T cells and macrophages. The CD8+ T cells were essential for the development of diabetes but not insulitis. The autoimmune diabetes and insulitis were completely prevented by the injection of a particular CD4+ T cell subset, isolated from healthy syngeneic donors, of the phenotype CD45RClow T cell receptor alpha/beta+ RT6+ Thy-1- OX-40-. Cells of this protective phenotype, which make up about 5% of thoracic duct lymphocytes, were found to provide help for secondary antibody responses and produce interleukin 2 (IL-2) and IL-4, but no interferon gamma, on in vitro activation. These data provide evidence for the presence of autoreactive T cells in the normal immune system of the rat and reveal that in the intact animal these cells are prevented from expressing their autoreactive potential by other T cells.

Suppressor T lymphocyte dysfunction is important in the pathogenesis of autoimmune thyroid disease: a perspective

Over the past decade, there was considerable scepticism regarding the existence, nature, and function of suppressor T (Ts) lymphocytes, particularly antigen-specific Ts lymphocytes. The receptors of putative antigen-specific murine Ts hybrids revealed that most either lacked the T cell receptor beta (TCR beta) chain or had failed to properly rearrange them and thus could not make a functional receptor. Moreover, studies of the DNA of sequences of the MHC I-J region (considered an important determinant for suppression) fail to show evidence for a unique open reading frame capable of encoding the I-J restriction element. In addition, no molecular basis for suppression had been characterized. These criticisms have now been satisfactorily resolved and the pendulum is swinging in favor of participation by antigen-specific Ts lymphocytes in immune tolerance. Ts lymphocytes have now been cloned and cell lines have been found to be idiotypic-specific. Indeed, specific Ts lymphocytes in the periphery have been shown to prevent the appearance of autoreactivity. It is, therefore, legitimate to consider their control as part of the mechanisms of maintaining the integrity of the immune system. Moreover, all human primary Ts clones and the majority of murine Ts clones have now been shown to rearrange TCR alpha beta. Ts lymphocytes are induced by antigen via antigen-presenting cells (APCs), and may do so in the context of MHC class II antigens, a concept not previously accepted. Moreover, there is now considerable evidence that such cells many well be involved in various autoimmune disease states.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for target tissue regulation of resistance to the induction of experimental allergic encephalomyelitis in AO rats

A myelin basic protein (MBP)-specific T cell line derived from F1 hybrids between experimental allergic encephalomyelitis (EAE)-susceptible DA (RT1avl) strain and EAE-resistant AO (RT1u) strain was capable of inducing clinical EAE in F1 hybrids and DA, but not in AO rats. In vitro restimulation with MBP presented by AO antigen-presenting cells (APC) resulted in the generation of a MBP-specific subline restricted by RT1u MHC products which induced clinical EAE in F1 hybrids but not in the AO parental strain. Deletion of hosts' leukocytes using sublethal irradiation and cytotoxic drugs did not abrogate the resistance of AO rats, which argues against the involvement of hosts' lymphoid cells in the regulation of autoagression. Thus, mechanism(s) regulating the activity of autoagressive T cells on functional elements in the target tissue might be responsible for differences in susceptibility to EAE.

Administration of interleukin-2 induces major histocompatibility complex class II expression on the biliary epithelial cells, possibly through endogenous interferon-gamma production

In various organ-specific autoimmune diseases, aberrant expression of major histocompatibility complex class II antigens on each target epithelial cell has been reported. Some researchers have attempted to link this phenomenon to the antigen-presenting capacity and the induction of autoimmunity, whereas others think it might serve as a peripheral mechanism for the induction and the maintenance of self-tolerance in autoreactive T cells. In this study, we showed that intraperitoneal administration of interleukin-2 (1.2 x 10(6) IU/kg) to 4-wk-old male BALB/c mice for 35 consecutive days induced lymphocyte infiltration around bile ducts in the liver and major histocompatibility complex class II expression on biliary epithelial cells, which was immunoelectron microscopically confined to the luminal cell surface. Immunohistochemically, lymphocytes accumulating around bile ducts were mainly T cells, positive for CD3, L3T4 and H-2 class II molecules, and a few of them were positive for Lyt-2 and negative for immunoglobulin. Half of the infiltrates were positive for asialo GM1, and one-third was positive for interferon-gamma. Interferon-gamma-positive, L3T4-positive cells were detected in mirror sections. However, neither the destruction of biliary epithelial cells nor the presence of granulomas was observed. Autoantibodies were serologically undetectable. The existence of interferon-gamma-positive cells in the lesion and the fact that intravenous administration of anti-interferon-gamma twice a week completely inhibited the lymphocyte infiltration and the major histocompatibility complex class II expression on biliary epithelial cells suggested that these changes were induced through endogenous interferon-gamma production.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression of efferent limb of testicular autoimmune response by a regulatory CD4+ T cell line in mice

A murine T cell line (designated as C.Ts) as a mediator of suppression of experimental autoimmune orchitis (EAO) was established. The method of establishment of C.Ts cell line was preparing spleen cells from C3H/He mice hyperimmunized with testicular germ cells (TC) and the repeated selection of the lymphocytes in vitro by stimulation with mouse testicular antigens (mTA). The C.Ts cells were Thy1.2+, surface immunoglobulin-, CD3+, CD4+ and CD8-. The cells could suppress the induction of EAO when transferred into actively EAO-sensitized mice only at the pre-clinical stage of the disease (efferent limb of the autoimmune response). The transferred C.Ts cells significantly inhibited both cellular and humoral immune responses to TC in the recipients in an antigen-specific manner. The disease suppression by C.Ts cells was found to depend upon their cell number, and their suppressive activity was markedly augmented by in vitro stimulation with mTA.

Regulation of autoimmunity

Despite the prevalence of self-reactive T cells, the healthy organism is not in a state of all-out war. Potent regulatory mechanisms exist at every level to permit the successful integration of the various aspects of the immune system, allowing only minor skirmishes, which ordinarily can be neutralized.

Dual colour fluorescein analysis of peripheral blood T cells in auto-immune chronic active hepatitis

Both CD4 and CD8 T cells are subdivided into two phenotypically distinct sublineages via another two T cell markers, Leu-8 and CD11b antigens. The proportions of these four T cell subsets, CD4+Leu8+, CD4+Leu8-, CD8+11b+ and CD8+11b-, were studied in patients with auto-immune chronic active hepatitis (CAH) and compared with disease controls (hepatitis B surface antigen positive chronic active hepatitis) and healthy controls. We found that the proportion of CD4+Leu8+ cells was significantly reduced compared with controls (P less than 0.01), whereas those of the other cells were almost identical in all 3 groups. The absolute number of these CD4+Leu8+ cells was also lower than that of controls (P less than 0.01). Thus, the present study suggests that a reduced number of CD4+Leu8+ cells is associated with the aberrant immune response in auto-immune CAH.

OX-22high CD4+ T cells induce wasting disease with multiple organ pathology: prevention by the OX-22low subset

Congenitally athymic rats injected with CD45RBhigh CD4+ T cells from congenic euthymic donors developed a severe wasting disease with inflammatory infiltrates in liver, lung, stomach, thyroid, and pancreas. In contrast, recipients of CD45RBlow CD4+ T cells remained well and continued to gain weight. Animals given unfractionated CD4+ T cells, i.e., a mixture of approximately two-thirds CD45RBhigh and one-third CD45RBlow, were protected from the wasting disease, and the incidence of organ-specific inflammation was much reduced compared with that found in recipients of CD45RBhigh cells alone. The data suggest that this latter subset of CD4+ T cells has autoaggressive potential that is inhibited in normal animals by cells of the CD45RBlow CD4+ phenotype. The possible consequences of a breakdown in this immunoregulatory mechanism are briefly discussed.