Frequency and function of circulating invariant NKT cells in autoimmune diabetes mellitus and thyroid diseases in Colombian patients

Innate Immunity in Autoimmune Thyroid Disease during Pregnancy

Autoimmune thyroid disease (AITD) is the most common organ-specific autoimmune disorder clinically presented as Hashimoto thyroiditis (HT) and Graves' disease (GD). The pathogenesis of AITD is caused by an inappropriate immune response related to genetic, non-genetic, and environmental factors. Pregnancy is one of the factors that have a great influence on the function of the thyroid gland because of the increased metabolic demand and the effects of hormones related to pregnancy. During pregnancy, an adaptation of the maternal immune system occurs, especially of the innate immune system engaged in maintaining adaptive immunity in the tolerant state, preventing the rejection of the fetus. Pregnancy-related hormonal changes (estrogen, progesterone, hCG) may modulate the activity of innate immune cells, potentially worsening the course of AITD during pregnancy. This especially applies to NK cells, which are associated with exacerbation of HD and GD. On the other hand, previous thyroid disorders can affect fertility and cause adverse outcomes of pregnancy, such as placental abruption, spontaneous abortion, and premature delivery. Additionally, it can cause fetal growth retardation and may contribute to impaired neuropsychological development of the fetus. Therefore, maintaining the thyroid equilibrium in women of reproductive age and in pregnant women is of the highest importance.

The proportion of peripheral blood Tregs among the CD4+ T cells of autoimmune thyroid disease patients: a meta-analysis

Autoimmune thyroid disease (AITD) is characterized by a loss of self-tolerance to thyroid antigen. Tregs, whose proportions are controversial among CD4+ T cell from AITD patients (AITDs), are crucial in immune tolerance. Considering that drugs might affect Treg levels, we assumed that the differences originated from different treatment statuses. Thus, we performed a meta-analysis to explore proportions of Tregs in untreated and treated AITDs. PubMed, Embase and ISI Web of Knowledge were searched for relevant studies. Review Manager 5.3 and Stata 14.0 were used to conduct the meta-analysis. Subgroup analysis based on different diseases and cell surface markers was performed. Egger linear regression analysis was used to assess publication bias. Approximately 1,100 AITDs and healthy controls (HCs) from fourteen studies were included. Proportions of Tregs among CD4+ T cells of untreated AITDs were significantly lower than those in HCs (p = 0.002), but were not in treated patients (p = 0.40). Subgroup analysis revealed lower proportions of Tregs in untreated Graves' disease patients (GDs) (p = 0.001) but did not show obvious differences in untreated Hashimoto's thyroiditis patients (HTs) (p = 0.62). Furthermore, proportions of circulating FoxP3+ Tregs were reduced in untreated GDs (p < 0.00001) and HTs (p = 0.04). No publication bias was found. In this first meta-analysis exploring proportions of circulating Tregs among CD4+ T cells of AITDs with different treatment statuses, we found that Tregs potentially contribute to the pathogenesis of AITD but function differently in GD and HT. Remarkably, FoxP3+ Tregs, which were decreased in both diseases, might be promising targets for novel therapies.

The Clonal Invariant NKT Cell Repertoire in People with Type 1 Diabetes Is Characterized by a Loss of Clones Expressing High-Affinity TCRs

Invariant NKT (iNKT) cells in healthy people express iNKT-TCRs with widely varying affinities for CD1d, suggesting different roles for high- and low-affinity iNKT clones in immune regulation. However, the functional implications of this heterogeneity have not yet been determined. Functionally aberrant iNKT responses have been previously demonstrated in different autoimmune diseases, including human type 1 diabetes, but their relationship to changes in the iNKT clonal repertoire have not been addressed. In this study, we directly compared the clonal iNKT repertoire of people with recent onset type 1 diabetes and age- and gender-matched healthy controls with regard to iNKT-TCR affinity and cytokine production. Our results demonstrate a selective loss of clones expressing high-affinity iNKT-TCRs from the iNKT repertoire of people with type 1 diabetes. Furthermore, this bias in the clonal iNKT repertoire in type 1 diabetes was associated with increased GM-CSF, IL-4, and IL-13 cytokine secretion among Ag-stimulated low-affinity iNKT clones. Thus, qualitative changes of the clonal iNKT repertoire with the potential to affect the regulatory function of this highly conserved T cell population are already established at the early stages in type 1 diabetes. These findings may inform future rationales for the development of iNKT-based therapies aiming to restore immune tolerance in type 1 diabetes.

Impaired immune regulation after radioiodine therapy for Graves' disease and the protective effect of Methimazole

Both therapies for Graves' disease (GD), radioactive iodine (RAI) and antithyroid drugs (ATD), were reported to have specific immune effects. We aimed at investigating the effects of RAI therapy on cellular subsets involved in immune regulation. We conducted a thirty day follow-up prospective cohort study of adult patients. Patients eligible for RAI therapy at our centre were approached. Twenty seven patients with GD were recruited, among whom 11 were treated with ATD. Twenty-two healthy subjects (HS) were also studied. Over time, frequency of regulatory T cells (Treg) and of invariant natural killer T cells (iNKT), along with Treg cell-mediated suppression and underlying mechanisms, were monitored in the peripheral blood. Variance in frequency of Treg and iNKT after RAI therapy was higher in GD patients than in HS over time (p < 0.0001). Reduced Treg suppressive function was observed after RAI therapy in GD patients (p = 0.002). ATD medication prior to RAI dampened these outcomes: less variation of Treg frequency (p = 0.0394), a trend toward less impaired Treg function, and prevention of reduced levels of suppressive cytokines (p < 0.05). Shortly after RAI therapy, alterations in immunoregulatory cells in patients with GD were observed and partially prevented by an ATD pretreatment. Worsening of autoimmunity after RAI was explained in previous studies by enhanced immune activity. This study adds new highlights on immune regulation deficiencies after therapeutic interventions in thyroid autoimmunity.

Regulatory role of natural killer T cells in diabetes

Type 1 and type 2 diabetes are growing public health problems. Despite having different pathophysiologies, both diseases are associated with defects in immune regulation. Invariant natural killer T (iNKT) cells are innate-like T cells that recognize glycolipids presented by CD1d. These cells not only play a key role in the defense against pathogens, but also exert potent immunoregulatory functions. The regulatory role of iNKT cells in the prevention of type 1 diabetes has been demonstrated in murine models and analyzed in diabetic patients. The decreased frequency of iNKT cells in non-obese diabetic mice initially suggested the regulatory role of this cell subset. Increasing the frequency or the activation of iNKT cells with agonists protects non-obese diabetic mice from the development of diabetes. Several mechanisms mediate iNKT regulatory functions. They can rapidly produce immunoregulatory cytokines, interleukin (IL)-4 and IL-10. They induce tolerogenic dendritic cells, thereby inducing the anergy of autoreactive anti-islet T cells and increasing the frequency of T regulatory cells (Treg cells). Synthetic agonists are able to activate iNKT cells and represent potential therapeutic treatment in order to prevent type 1 diabetes. Growing evidence points to a role of immune system in glucose intolerance and type 2 diabetes. iNKT cells are resident cells of adipose tissue and their local and systemic frequencies are reduced in obese patients, suggesting their involvement in local and systemic inflammation during obesity. With the discovery of potential continuity between type 1 and type 2 diabetes in some patients, the role of iNKT cells in these diseases deserves further investigation.

Reduced iNKT cells numbers in type 1 diabetes patients and their first-degree relatives

Type 1 diabetes (T1D) is an autoimmune disease that is characterized by the specific destruction of insulin-producing pancreatic β cells. Invariant natural killer T (iNKT) cells have been associated with development of T1D. Class I MHC-restricted T cell-associated molecule (CRTAM) is expressed on activated iNKT, CD8(+), and CD4(+) T cells, and it is associated with the pro-inflammatory profiles of these cells. Crtam gene expression in CD3(+) lymphocytes from non-obese diabetic (NOD) mice is associated with T1D onset. However, expression of CRTAM on T cells from patients with T1D has not yet been evaluated. We compared iNKT cell (CD3(+)Vα24(+)Vβ11(+)) numbers and CRTAM expression in a Mexican population with recent-onset T1D and their first-degree relatives with control families. Remarkably, we found lower iNKT cell numbers in T1D families, and we identified two iNKT cell populations in some of the families. One iNKT cell population expressed high iTCR levels (iNKT(hi)), whereas another expressed low levels (iNKT(lo)) and also expressed CRTAM. These findings support a probable genetic determinant of iNKT cell numbers and a possible role for these cells in T1D development. This study also suggests that CRTAM identifies recently activated iNKT lymphocytes.

iNKT and MAIT Cell Alterations in Diabetes

Type 1 diabetes (T1D) and type 2 diabetes (T2D) are multifactorial diseases with different etiologies in which chronic inflammation takes place. Defects in invariant natural killer T (iNKT) cell populations have been reported in both T1D and T2D patients, mouse models and our recent study revealed mucosal-associated invariant T (MAIT) cell defects in T2D and obese patients. Regarding iNKT cells many studies in non-obese diabetic mice demonstrated their protective role against T1D whereas their potential role in human T1D is still under debate. Studies in mouse models and patients suggest that iNKT cells present in adipose tissue (AT) could exert a regulatory role against obesity and associated metabolic disorders, such as T2D. Scarce data are yet available on MAIT cells; however, we recently described MAIT cell abnormalities in the blood and ATs from obese and T2D patients. These data show that a link between MAIT cells and metabolic disorders pave the way for further investigations on MAIT cells in T1D and T2D in humans and mouse models. Furthermore, we hypothesize that the gut microbiota alterations associated with T1D and T2D could modulate iNKT and MAIT cell frequency and functions. The potential role of iNKT and MAIT cells in the regulation of metabolic pathways and their cross-talk with microbiota represent exciting new lines of research.

Regulatory Role of Natural Killer T Cells in Diabetes

Type 1 and type 2 diabetes are growing public health problems. Despite having different pathophysiologies, both diseases are associated with defects in immune regulation. Invariant natural killer T (iNKT) cells are innate-like T cells that recognize glycolipids presented by CD1d. These cells not only play a key role in the defense against pathogens, but also exert potent immunoregulatory functions. The regulatory role of iNKT cells in the prevention of type 1 diabetes has been demonstrated in murine models and analyzed in diabetic patients. The decreased frequency of iNKT cells in non-obese diabetic mice initially suggested the regulatory role of this cell subset. Increasing the frequency or the activation of iNKT cells with agonists protects non-obese diabetic mice from the development of diabetes. Several mechanisms mediate iNKT regulatory functions. They can rapidly produce immunoregulatory cytokines, interleukin (IL)-4 and IL-10. They induce tolerogenic dendritic cells, thereby inducing the anergy of autoreactive anti-islet T cells and increasing the frequency of T regulatory cells (Treg cells). Synthetic agonists are able to activate iNKT cells and represent potential therapeutic treatment in order to prevent type 1 diabetes. Growing evidence points to a role of immune system in glucose intolerance and type 2 diabetes. iNKT cells are resident cells of adipose tissue and their local and systemic frequencies are reduced in obese patients, suggesting their involvement in local and systemic inflammation during obesity. With the discovery of potential continuity between type 1 and type 2 diabetes in some patients, the role of iNKT cells in these diseases deserves further investigation.

Natural killer T cells: drivers or passengers in preventing human disease?

Natural killer T (NKT) cells are credited with regulatory roles in immunity against cancers, autoimmune diseases, allergies, and bacterial and viral infections. Studies in mice and observational research in patient groups have suggested that NKT cell-based therapies could be used to prevent or treat these diseases, yet the translation into clinical settings has been disappointing. We support the view that NKT cells have regulatory characteristics that could be exploited in clinical settings, but there are doubts about the natural roles of NKT cells in vivo and whether NKT cell defects are fundamental drivers of disease in humans. In this Opinion article, we discuss the uncertainties and opportunities regarding NKT cells in humans, and the potential for NKT cells to be manipulated to prevent or treat disease.

Genetic control of murine invariant natural killer T cells maps to multiple type 1 diabetes regions

Reduced frequency of invariant natural killer T (iNKT)-cells has been indicated as a contributing factor to type 1 diabetes (T1D) development in NOD mice. To further understand the genetic basis of the defect, we generated (NOD X ICR)F2 mice to map genes that control iNKT-cell development. We determined frequencies of thymic and splenic iNKT-cells as well as the ratio of CD4-positive and -negative subsets in the spleens of 209 F2 males. Quantitative trait loci (QTL) analysis revealed 5 loci that exceed the significant threshold for the frequency of thymic and/or splenic iNKT-cells on Chromosomes (Chr) 1, 5, 6, 12, and 17. Three significant loci on Chr 1, 4, and 5 were found for the ratio of CD4-positive and -negative splenic iNKT-cells. Comparisons to previously known mouse T1D susceptibility (Idd) loci revealed two significant QTL peak locations respectively mapped to Idd regions on Chr 4 and 6. The peak marker location of the significant Chr 12 iNKT QTL maps to within 0.5Mb of a syntenic human T1D locus. Collectively, our results reveal several novel loci controlling iNKT-cell development and provide additional information for future T1D genetic studies.

Cell-based interventions to halt autoimmunity in type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) results from death of insulin-secreting β cells mediated by self-immune cells, and the consequent inability of the body to maintain insulin levels for appropriate glucose homeostasis. Probably initiated by environmental factors, this disease takes place in genetically predisposed individuals. Given the autoimmune nature of T1DM, therapeutics targeting immune cells involved in disease progress have been explored over the last decade. Several high-cost trials have been attempted to prevent and/or reverse T1DM. Although a definitive solution to cure T1DM is not yet available, a large amount of information about its nature and development has contributed greatly to both the improvement of patient's health care and design of new treatments. In this study, we discuss the role of different types of immune cells involved in T1DM pathogenesis and their therapeutic potential as targets and/or modified tools to treat patients. Recently, encouraging results and new approaches to sustain remnant β cell mass and to increase β cell proliferation by different cell-based means have emerged. Results coming from ongoing clinical trials employing cell therapy designed to arrest T1DM will probably proliferate in the next few years. Strategies under consideration include infusion of several types of stem cells, dendritic cells and regulatory T cells, either manipulated genetically ex vivo or non-manipulated. Their use in combination approaches is another therapeutic alternative. Cell-based interventions, without undesirable side effects, directed to block the uncontrollable autoimmune response may become a clinical reality in the next few years for the treatment of patients with T1DM.

Helminth mediated modulation of Type 1 diabetes (T1D)

Type 1 diabetes is increasing dramatically in incidence in the developed world. While there may be several reasons for this, improved sanitation and public health measures have altered our interactions with certain infectious agents such as helminths. There is increasing interest in the use of helminths or their products to alleviate inflammatory or allergic conditions. Using rodent models of diabetes, it has been possible to explore the therapeutic potential of both live infections as well as helminth-derived products on the development of autoimmunity. This review provides an overview of the findings from animal models and additionally explores the potential for translation to the clinic.

Prevention and treatment of type 1 diabetes mellitus by the manipulation of invariant natural killer T cells

Invariant natural killer T (iNKT) cells are CD1d-restricted T cells with regulatory functions. iNKT cells are numerically and functionally deficient in experimental models of type 1 diabetes mellitus (T1DM). Moreover, various experimental strategies correcting the defect of or stimulating iNKT cells prevent T1DM. Here, we review the data on the role of iNKT cells in the development of T1DM and discuss indications, obstacles and prospects of the use of iNKT cell manipulations in the prevention and treatment of human T1DM.

Genetic control of murine invariant natural killer T-cell development dynamically differs dependent on the examined tissue type

Previous studies using gene-targeted mutant mice revealed several molecules important for the development or function of invariant natural killer T (iNKT) cells. However, these gene knockout mice represent cases that are rare in humans. Thus, it remains unclear how naturally occurring allelic variants of these genes or others regulate the numerical and functional diversity of iNKT cells in both mice and humans. Studies in humans are mostly limited to iNKT cells in peripheral blood (PB). It is not known if the relative distribution of iNKT cells between PB and other lymphoid organs is correlated or under common genetic control. To initially address these questions, we analyzed iNKT cells in the spleen, thymus and PB of 38 inbred mouse strains. Percentages of iNKT cells in these three anatomical sites varied significantly in a strain-dependent manner. The correlation between PB and spleen was moderate, and none was observed between PB and thymus. Similarly, proportions of the CD4-expressing subset of iNKT cells differed significantly among inbred strains. The percentages of CD4-positive iNKT cells displayed a strong correlation between PB and spleen, although it remained poor between PB and thymus. Genome-wide association studies across strains identified only partially overlapping loci associated with variability of iNKT cell frequencies within and between differing anatomical sites.

Presumed guilty: natural killer T cell defects and human disease

Natural killer T (NKT) cells are important regulatory lymphocytes that have been shown in mouse studies, to have a crucial role in promoting immunity to tumours, bacteria and viruses, and in suppressing cell-mediated autoimmunity. Many clinical studies have indicated that NKT cell deficiencies and functional defects might also contribute to similar human diseases, although there is no real consensus about the nature of the NKT cell defects or whether NKT cells could be important for the diagnosis and/or treatment of these conditions. In this Review, we describe the approaches that have been used to analyse the NKT cell populations of various patient groups, suggest new strategies to determine how (or indeed, if) NKT cell defects contribute to human disease, and discuss the prospects for using NKT cells for therapeutic benefit.

Role of SLAM in NKT cell development revealed by transgenic complementation in NOD mice

Allelic variation of SLAM expression on CD4(+)CD8(+) thymocytes has been proposed to play a major role in NKT cell development. In this article, this hypothesis is tested by the production of subcongenic mouse strains and Slamf1 transgenic lines. The long isoform of the C57BL/6 allele of Slamf1 was transgenically expressed on CD4(+)CD8(+) thymocytes under control of an hCD2 minigene. NOD.Nkrp1b.Tg(Slamf1)1 mice, which had a 2-fold increase in SLAM protein expression on CD4(+)CD8(+) thymocytes, had a 2-fold increase in numbers of thymic NKT cells. The additional thymic NKT cells in NOD.Nkrp1b.Tg(Slamf1)1 mice were relatively immature, with a similar subset distribution to those of congenic NOD.Nkrp1b.Nkt1 and NOD.Nkrp1b.Slamf1 mice, which also express increased levels of SLAM on CD4(+)CD8(+) thymocytes and produce larger numbers of NKT cells. Transgenic enhancement of SLAM expression also increased IL-4 and IL-17 production in response to TCR-mediated stimulation. Paradoxically, NOD.Nkrp1b.Tg(Slamf1)2 mice, which had a 7-fold increase in SLAM expression, showed no significant increase in NKT cells numbers; on the contrary, at high transgene copy number, SLAM expression levels correlated inversely with NKT cell numbers, consistent with a contribution to negative selection. These data confirm a role for SLAM in controlling NKT cell development and are consistent with a role in both positive and negative thymic selection of NKT cells.

Mechanism of regulation of autoimmunity by iNKT cells

iNKT cells, CD1d dependent natural killer T cells are a unique population of T cells. The capacity of iNKT cells to produce regulatory cytokines first provided an indication of their regulatory potential. Later on, in experimental models as well as in patients afflicted with an auto-immune disease, such as Type 1 diabetes mellitus, multiple sclerosis, and systemic lupus erythematosus along with others, a deficit in iNKT cell number was observed, suggesting the role these cells may possibly have in the prevention of auto-immune diseases. More importantly, experimental strategies which focused on increasing the volume or stimulation of iNKT cells in laboratory animals, demonstrated an improved level of protection against the development of auto-immune diseases. This article reviews the mechanism of protection against autoimmunity by iNKT cells, discusses the obstacles against and indications for the potential use of iNKT cell manipulation in the treatment of human auto-immune diseases.

Numerical defects in CD8+CD28- T-suppressor lymphocyte population in patients with type 1 diabetes mellitus and multiple sclerosis

Type 1 diabetes mellitus (T1D) and multiple sclerosis (MS) are organ-specific autoimmune diseases leading to an attack of auto-aggressive lymphocytes against the pancreatic beta-cells and central nervous system, respectively. Using four-colour flow cytometry, T-lymphocyte populations having an important function in autoimmune processes were analyzed. T-regulatory cells (Treg) CD4(+)CD25(+)CD127(low), T-suppressor cells (Ts) CD8(+)CD28(-), activated helper CD4(+)CD25(+)CD127(+) and cytotoxic CD8(+)CD25(+) T-cells and also naive CD4(+)CD45RA(+) and memory T-cells CD4(+)CD45RO(+) were compared in the group of patients with T1D (n=30), MS (n=31) and in the group of healthy controls (n=29). Significant differences in Ts cells, activated helper and cytotoxic cells and also memory T-cells were recognized in the group of T1D patients compared to healthy controls. Ts population was significantly lowered in MS patients as well. However, no significant differences were noticed in Treg population. The observed data demonstrate significant differences among patients with T1D and MS in comparison to healthy individuals.