Regulatory T-cells in the control of immunological diseases

Impaired Treg and NK cells profile in overweight women with gestational diabetes mellitus

PROBLEM

Maternal obesity is frequently associated with gestational diabetes mellitus (GDM), and immunological mechanisms seem to be involved in the physiopathology of these conditions. The aim of this study was to characterize the profile of immune cells in peripheral blood of overweight women with GDM.

METHOD OF STUDY

This case-control study included 27 glucose-tolerant (controls) and 31 GDM overweight pregnant women. Flow cytometry was used to assess the number of regulatory T cells (Treg) and natural killer (NK) cells in the peripheral blood. In addition, the expression of IL-10, TGF-B, and TNF-A in Treg and expression of IFN-G, TNF-A, granzyme, and perforin in NK cells were analyzed.

RESULTS

GDM patients had significantly lower frequency of TCD4⁺ CD25^bright and TCD4⁺ CD25⁺ FOXP3^high cells, higher production of TNF-A by Treg cells and higher percentage of NKCD16⁺ 56^dim cells than the controls.

CONCLUSION

The association between obesity and GDM is a condition where it is observed impaired Treg and NK cells profile, findings that seem to be related with the development of IR and inflammation.

Rationale and Design of the ARREST Trial Investigating Mesenchymal Stem Cells in the Treatment of Small Abdominal Aortic Aneurysm

BACKGROUND

Abdominal aortic aneurysms (AAAs) are a major source of morbidity and mortality despite continuing advances in surgical technique and care. Although the inciting factors for AAA development continue to be elusive, accumulating evidence suggests a significant periaortic inflammatory response leading to degradation and dilation of the aortic wall. Previous human trials have demonstrated safety and efficacy of mesenchymal stem cells (MSCs) in the treatment of inflammation-related pathologies such as rheumatoid arthritis, graft versus host disease, and transplant rejection. Therefore, herein, we describe the Aortic Aneurysm Repression with Mesenchymal Stem Cells (ARREST) trial, a phase I investigation into the safety of MSC infusion for patients with small AAA and the cells' effects on modulation of AAA-related inflammation.

METHODS

ARREST is a phase I, single-center, double-blind, randomized controlled trial (RCT) investigating infusion both dilute and concentrated MSCs compared to placebo in 36 small AAA (35-45 mm) patients. Subjects will be followed by study personnel for 12 months to ascertain incidence of adverse events, immune cell phenotype expression, peripheral cytokine profile, and periaortic inflammation. Maximum transverse aortic diameter will be assessed regularly for 5 years by a combination of computed tomography and duplex sonography.

RESULTS

Four patients have thus far been enrolled, randomized, and treated per protocol. We anticipate the conclusion of the treatment phase within the next 24 months with ongoing long-term follow-up.

CONCLUSIONS

ARREST will be pivotal in assessing the safety of MSC infusion and provide preliminary data on the ability of MSCs to favorably modulate the pathogenic AAA host immune response. The data gleaned from this phase I trial will provide the groundwork for a larger, phase III RCT which may provide the first pharmaceutical intervention for AAA.

Type 1 diabetes and T regulatory cells

T-regulatory cells (Tregs) play a fundamental role in the creation and maintenance of peripheral tolerance. Deficits in the numbers and/or function of Tregs may be an underlying cause of human autoimmune diseases including type 1 Diabetes Mellitus (T1D), whereas an over-abundance of Tregs can hinder immunity against cancer or pathogens. The importance of Tregs in the control of autoimmunity is well established in a variety of experimental animal models. In mice, manipulating the numbers and/or function of Tregs can decrease pathology in a wide range of contexts, including autoimmunity and it is widely assumed that similar approaches will be possible in humans. T1D, the most prevalent human autoimmune disease, has been a focus of interventions either through direct and indirect in vivo proliferations or through adoptive transfer of the in vitro generated antigen specific and non specific Treg. Some challenges still need to be addressed, including a more specific phenotype marker for Tregs; the reproducibility of satisfactory animal results in human and the reconcile of discrepancies between in vitro and in vivo studies. In this article, we will highlight the role of Tregs in autoimmune disease in general with a special focus on T1D, highlighting progress made and challenges ahead in developing Treg-based therapies.

HLA DRB1*1503 allelic haplotype predominance and associated immunodysregulation in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic, relapsing, and remitting disease affecting primarily African American females of child bearing age. Familial aggregation of this disease suggests that at least part of the susceptibility for this disease is genetic, although environmental and hormonal influences are also likely to play a role. Early studies of genetic susceptibility to SLE revealed several of the major histocompatibility complex molecules, namely HLA DR, to be linked to SLE. Meta-analysis of genome scans has yielded loci significant for lupus patients, one of which includes the MHC region. Regulatory T cells are immunoregulatory cells that modulate activated immune cells. These cells play a large role in homeostasis of the immune responses and maintenance of immunologic tolerance, i.e., prevention of autoimmunity. Decreased numbers of regulatory T cells have been described in many autoimmune diseases, including systemic lupus erythematosus. Autoantibody production in systemic lupus erythematosus and the resulting immune complex formation and complex deposition into tissues are arguably the central core of immune dysregulation leading to disease manifestations and symptoms. Inability of the immune system to recognize and inhibit autoreactive immune cells in this particular autoimmune disease may be the result of inappropriate numbers and function of regulatory T cells. This study aims to characterize the immune cell population in patients from our community suffering from systemic lupus erythematosus and to prove that these patients exhibit a unique cellular profile compared to healthy age, race and gender matched control subjects. Surprisingly, our findings demonstrate that patients from the local Mississippi area exhibit increased proportions of CD25(+) FoxP3(+) regulatory T cells and CD25(+) FoxP3(-) T cells (of CD45(+) CD3(+) CD4(+) helper T cells) as compared to healthy controls. HLA tissue-typing of these lupus patients revealed a prominent subgroup (~30%) of patients possessing the HLA DRB1*1503 allele. The investigation of this subgroup demonstrated regulatory T cell composition similar to that of the total lupus group and to that of the non-HLA DRB1*1503 subgroup. Genetic analysis for molecular gene expression levels of various lupus-associated genes by real-time PCR demonstrated a unique profile as compared to healthy controls. Increased gene expression of FoxP3 together with decreased gene expression levels of GATA3, TNFAIP3, and TNFSF4 suggest that variations in gene products compared to healthy controls may be playing a role in the immune cell dysregulation and disproportionate CD25(+) FoxP3(+) regulatory T cells.

Deficient CD4 + CD25 + T Regulatory Cell Function in Patients With Abdominal Aortic Aneurysms

Objective— Increasing evidence shows that autoimmune response contributes importantly to pathogenesis of abdominal aortic aneurysm (AAA). This work was aimed to assess the possibly altered function of peripheral CD4 + CD25 + T regulatory cells (Tregs) that might breakdown immunologic self-tolerance in AAA patients.

Methods and Results— Peripheral blood from 22 AAA patients, 11 patients with abdominal aortic atherosclerotic occlusive disease (AOD), and 32 healthy controls (HCs) was analyzed to determine the percentage of CD4 + CD25 + Tregs in the total CD4 + T-cell population and FOXP3 expression by means of flow cytometry. The frequencies of the CD4 + CD25 + Treg population were not significantly different between groups (AAA, 5.69±0.99%; AOD, 5.52±1.13%; HC, 5.88±1.55%; P >0.05). However, the frequency of CD4 + CD25 + FOXP3 + T cells in AAA patients (2.45±0.57%) was significantly lower than that in AOD group (3.41±0.72%; P <0.01) or in HCs (3.69±0.82%; P <0.01). A comparison of FOXP3 mRNA and protein expression revealed significantly lower levels in CD4 + CD25 + Tregs from AAA group than either of other 2 groups ( P <0.01). Suppressive function assay showed that freshly isolated CD4 + CD25 + Tregs from patients with AAA exhibited significantly less suppressive activity than those from AOD patients or HCs ( P <0.01). Mixing cultures with CD4 + CD25 + T cells and CD4 + CD25 − T cells from AAA patients and HCs demonstrated that the primary regulatory defect is due to a dysfunction of CD4 + CD25 + Tregs, and not a resistance of CD4 + CD25 − responder T cells to suppression in AAA patients.

Conclusion— Our data demonstrate a reduced level of FOXP3 expression in peripheral CD4 + CD25 + Tregs and decreased frequency of CD4 + CD25 + FOXP3 + T cells in a cohort of AAA patients enrolled in the study, which leads to a functional deficiency of CD4 + CD25 + Tregs as a whole. This indicates an impaired immunoregulation by Tregs that may contribute to AAA pathogenesis.

Multiple roles for CD4+ T cells in anti-tumor immune responses

Our understanding of the importance of CD4+ T cells in orchestrating immune responses has grown dramatically over the past decade. This lymphocyte family consists of diverse subsets ranging from interferon-gamma (IFN-gamma)-producing T-helper 1 (Th1) cells to transforming growth factor-beta (TGF-beta)-secreting T-regulatory cells, which have opposite roles in modulating immune responses to pathogens, tumor cells, and self-antigens. This review briefly addresses the various T-cell subsets within the CD4+ T-cell family and discusses recent research efforts aimed at elucidating the nature of the 'T-cell help' that has been shown to be essential for optimal immune function. Particular attention is paid to the role of Th cells in tumor immunotherapy. We review some of our own work in the field describing how CD4+ Th cells can enhance anti-tumor cytotoxic T-lymphocyte (CTL) responses by enhancing clonal expansion at the tumor site, preventing activation-induced cell death and functioning as antigen-presenting cells for CTLs to preferentially generate immune memory cells. These unconventional roles for Th lymphocytes, which require direct cell-to-cell communication with CTLs, are clear examples of how versatile these immunoregulatory cells are.

Suppressive efficacy and proliferative capacity of human regulatory T cells in allogeneic and xenogeneic responses

BACKGROUND

An understanding of the mechanisms that suppress the human anti-pig cellular response is key for xenotransplantation. We have compared the ability of human regulatory T cells (Tregs) to suppress xenogeneic and allogeneic responses in vitro.

METHODS

Human peripheral blood mononuclear cells (PBMC), CD4+ T cells, or CD4+ CD25- T cells were stimulated with irradiated human or wild type (WT) or alpha1,3-galactosyltransferase gene-knockout (GT-KO) pig PBMC in the presence or absence of human CD4+ CD25 high Tregs. In separate experiments, 5- (and 6)-carboxyfluorescein diacetate succinimidyl ester-labeled human CD4+ T cells were stimulated with human or pig PBMC. The expansion and precursor frequencies of allo- and xenoreactive Tregs were assessed by labeling with FoxP3 mAb and flow cytometric analysis.

RESULTS

The responses of human PBMC, CD4+ T cells, and CD4+ CD25- T cells to pig PBMC were stronger than to human PBMC (P<0.05). Human anti-GT-KO responses were weaker than anti-WT responses (P<0.05). Human CD4+ CD25 high Tregs suppressed proliferation of CD4+ CD25- T cells to both human and pig PBMC stimulator cells with the same efficiency. Alloreactive CD4+ CD25+ FoxP3 high responder T cells proliferated more than their xenoreactive counterparts (P<0.05), although xenoreactive CD4+ CD25+ T cells proliferated more than alloreactive cells (P<0.05). There was no difference in precursor frequency between allo- and xeno-reactive CD4+ CD25+ FoxP3 high cells.

CONCLUSIONS

Human T-cell responses to pig cells are stronger than to allogeneic cells. The human response to GT-KO PBMC is weaker than to WT PBMC. Although human Tregs can suppress both responses, expansion of CD4+ CD25+ FoxP3 high cells against pig PBMC is weaker than against human PBMC. More human Tregs may be required to suppress the stronger xenogeneic response.

Regulatory T cells as therapeutic target in Hodgkin's lymphoma

BACKGROUND

The clinical and pathological features of Hodgkin's lymphoma (HL) reflect an abnormal immune response that results from cytokines and chemokines secreted by Hodgkin/Reed-Sternberg (H/R-S) cells and/or the surrounding tissue.

OBJECTIVE

Increasing evidence indicates that H/R-S cells recruit and/or induce regulatory T (Treg) cells that contribute to an ineffective immune clearance of the malignant cell types and may also impair effects of adaptive cellular immunotherapy applied in HL.

METHODS

In this review we highlight advances in the understanding of immune regulation in HL, and discuss implications for immunotherapy in this disease by targeting Treg cells. However, the origin, development, migration and functional mechanism of these Treg cells are under discussion.

RESULTS/CONCLUSION

As studies demonstrate that the depletion and/or manipulation of Treg cells enhance antitumor immunity, these novel treatment approaches may improve the therapy especially for patients with refractory or relapsed HL.