CD4+ CD25+ Treg cells inhibit human memory gammadelta T cells to produce IFN-gamma in response to M tuberculosis antigen ESAT-6. Blood. 2008;111:5629-5636. [PMID: 18388182 DOI: 10.1182/blood-2008-02-139899]

Foxp3+ Treg control allergic skin inflammation by restricting IFN-γ-driven neutrophilic infiltration and NETosis

BACKGROUND

Atopic dermatitis (AD), a chronic inflammatory skin disease with T cell activation as a key feature, in which Th2 cell-mediated responses play a pivotal role. Regulatory T cells (Treg) are central immune cells that restrict autoimmunity and inflammation in the body. Patients with immune dysregulation, polyendocrinopathy, or enteropathy X-linked syndrome, an immune disease characterized by a deficiency in Treg, develop skin inflammation and allergic disorders, indicating that Treg play a crucial role in the development of allergic skin inflammation.

OBJECTIVE

we investigated the underlying mechanisms by which Treg control cutaneous allergic inflammation.

METHODS

An allergic skin inflammation mouse model was constructed using MC903, and Treg-depleted mouse model was constructed using diphtheria toxin. Neutralization of IFN-γ was constructed using anti-mouse-IFN-γ mouse antibody. Neutrophil infiltration was analyzed by flow cytometry and immunohistochemistry. Neutrophil extracellular traps (NETs), a process called NETosis, were detected using immunofluorescence. In vitro neutrophil stimulation and immunocytochemistry was conducted to demonstrate the effect of IFN-γ on NETosis.

RESULTS

The depletion of Foxp3+ Treg led to significantly exacerbated AD-like skin inflammation, including increased recruitment of neutrophils and expression of Th1 cytokine IFN-γ. Neutrophil infiltrating in skin of Treg-depleted mice released more NETs than wild type. Neutralization of IFN-γ abolished neutrophil infiltration and NETosis in Treg-depleted mice. Neutrophils stimulated with IFN-γ were more prone to release NETs in vitro. Finally, Foxp3+ Treg control cutaneous allergic inflammation by regulating IFN-γ-driven neutrophilic infiltration and NETosis.

CONCLUSION

Our results highlight the previously underestimated Treg-IFN-γ-neutrophil inflammatory axis.

Revisiting regulatory T cells as modulators of innate immune response and inflammatory diseases

Regulatory T cells (Treg) are known to be critical for the maintenance of immune homeostasis by suppressing the activation of auto- or allo-reactive effector T cells through a diverse repertoire of molecular mechanisms. Accordingly, therapeutic strategies aimed at enhancing Treg numbers or potency in the setting of autoimmunity and allogeneic transplants have been energetically pursued and are beginning to yield some encouraging outcomes in early phase clinical trials. Less well recognized from a translational perspective, however, has been the mounting body of evidence that Treg directly modulate most aspects of innate immune response under a range of different acute and chronic disease conditions. Recognizing this aspect of Treg immune modulatory function provides a bridge for the application of Treg-based therapies to common medical conditions in which organ and tissue damage is mediated primarily by inflammation involving myeloid cells (mononuclear phagocytes, granulocytes) and innate lymphocytes (NK cells, NKT cells, γδ T cells and ILCs). In this review, we comprehensively summarize pre-clinical and human research that has revealed diverse modulatory effects of Treg and specific Treg subpopulations on the range of innate immune cell types. In each case, we emphasize the key mechanistic insights and the evidence that Treg interactions with innate immune effectors can have significant impacts on disease severity or treatment. Finally, we discuss the opportunities and challenges that exist for the application of Treg-based therapeutic interventions to three globally impactful, inflammatory conditions: type 2 diabetes and its end-organ complications, ischemia reperfusion injury and atherosclerosis.

Alleviating psoriatic skin inflammation through augmentation of Treg cells via CTLA-4 signaling peptide

Psoriasis is a chronic inflammatory skin disease characterized by hyperplasia of keratinocytes and immune cell infiltration. The IL-17-producing T cells play a key role in psoriasis pathogenesis, while regulatory T (Treg) cells are diminished during psoriatic inflammation. Current psoriasis treatments largely focus on IL-17 and IL-23, however, few studies have explored therapeutic drugs targeting an increase of Treg cells to control immune homeostasis. In this study, we investigated the effects of a cytotoxic T lymphocyte antigen-4 (CTLA-4) signaling peptide (dNP2-ctCTLA-4) in Th17, Tc17, γδ T cells, Treg cells in vitro and a mouse model of psoriasis. Treatment with dNP2-ctCTLA-4 peptide showed a significant reduction of psoriatic skin inflammation with increased Treg cell proportion and reduced IL-17 production by T cells, indicating a potential role in modulating psoriatic skin disease. We compared dNP2-ctCTLA-4 with CTLA-4-Ig and found that only dNP2-ctCTLA-4 ameliorated the psoriasis progression, with increased Treg cells and inhibited IL-17 production from γδ T cells. In vitro experiments using a T cell-antigen presenting cell co-culture system demonstrated the distinct mechanisms of dNP2-ctCTLA-4 compared to CTLA-4-Ig in the induction of Treg cells. These findings highlight the therapeutic potential of dNP2-ctCTLA-4 peptide in psoriasis by augmenting Treg/Teff ratio, offering a new approach to modulating the disease.

γδ T Lymphocytes as a Double-Edged Sword-State of the Art in Gynecological Diseases

Human gamma-delta (γδ) T cells are a heterogeneous cell population that bridges the gap between innate and acquired immunity. They are involved in a variety of immunological processes, including tumor escape mechanisms. However, by being prolific cytokine producers, these lymphocytes also participate in antitumor cytotoxicity. Which one of the two possibilities takes place depends on the tumor microenvironment (TME) and the subpopulation of γδ T lymphocytes. The aim of this paper is to summarize existing knowledge about the phenotype and dual role of γδ T cells in cancers, including ovarian cancer (OC). OC is the third most common gynecological cancer and the most lethal gynecological malignancy. Anticancer immunity in OC is modulated by the TME, including by immunosuppressive cells, cytokines, and soluble factors. Immune cells are exposed in the TME to many signals that determine their immunophenotype and can manipulate their functions. The significance of γδ T cells in the pathophysiology of OC is enigmatic and remains to be investigated.

Differential activation of innate and adaptive lymphocytes during latent or active infection with Mycobacterium tuberculosis

Most individuals infected with Mycobacterium tuberculosis (Mtb) have latent tuberculosis (TB), which can be diagnosed with tests (like the QuantiFERON test, QFT) that detect the production of IFN-γ by memory T cells in response to the Mtb-specific antigens ESAT-6, CFP-10 and TB7.7. However, the immunological mechanisms that determine if an individual will develop latent or active TB remain incompletely understood. Here we compared the response of innate and adaptive peripheral blood lymphocytes from healthy individuals without Mtb infection (QFT-negative) and from individuals with latent (QFT-positive) or active TB infection, in order to determine the characteristics of these cells that correlate with each condition. In active TB patients, the levels of IFN-γ that were produced in response to Mtb-specific antigens had high positive correlations with IL-1β, TNF-α, MCP-1, IL-6, IL-12p70 and IL-23, while the pro-inflammatory cytokines had high positive correlations between themselves and with IL-12p70 and IL-23. These correlations were not observed in QFT-negative or QFT-positive healthy volunteers. Activation with Mtb soluble extract (a mixture of Mtb antigens and pathogen-associated molecular patterns [PAMPs]) increased the percentage of IFN-γ/IL-17-producing NK cells and of IL-17-producing ILC3 in the peripheral blood of active TB patients, but not of QFT-negative or QFT-positive healthy volunteers. Thus, active TB patients have both adaptive and innate lymphocyte subsets that produce characteristic cytokine profiles in response to Mtb-specific antigens or PAMPs. These profiles are not observed in uninfected individuals or in individuals with latent TB, suggesting that they are a response to active TB infection. This article is protected by copyright. All rights reserved.

Comorbidity-associated glutamine deficiency is a predisposition to severe COVID-19

SARS-CoV-2 vaccinations have greatly reduced COVID-19 cases, but we must continue to develop our understanding of the nature of the disease and its effects on human immunity. Previously, we suggested that a dysregulated STAT3 pathway following SARS-Co-2 infection ultimately leads to PAI-1 activation and cascades of pathologies. The major COVID-19-associated metabolic risks (old age, hypertension, cardiovascular diseases, diabetes, and obesity) share high PAI-1 levels and could predispose certain groups to severe COVID-19 complications. In this review article, we describe the common metabolic profile that is shared between all of these high-risk groups and COVID-19. This profile not only involves high levels of PAI-1 and STAT3 as previously described, but also includes low levels of glutamine and NAD+, coupled with overproduction of hyaluronan (HA). SARS-CoV-2 infection exacerbates this metabolic imbalance and predisposes these patients to the severe pathophysiologies of COVID-19, including the involvement of NETs (neutrophil extracellular traps) and HA overproduction in the lung. While hyperinflammation due to proinflammatory cytokine overproduction has been frequently documented, it is recently recognized that the immune response is markedly suppressed in some cases by the expansion and activity of MDSCs (myeloid-derived suppressor cells) and FoxP3+ Tregs (regulatory T cells). The metabolomics profiles of severe COVID-19 patients and patients with advanced cancer are similar, and in high-risk patients, SARS-CoV-2 infection leads to aberrant STAT3 activation, which promotes a cancer-like metabolism. We propose that glutamine deficiency and overproduced HA is the central metabolic characteristic of COVID-19 and its high-risk groups. We suggest the usage of glutamine supplementation and the repurposing of cancer drugs to prevent the development of severe COVID-19 pneumonia.

Decreased Frequencies of Gamma/Delta T Cells Expressing Th1/Th17 Cytokine, Cytotoxic, and Immune Markers in Latent Tuberculosis-Diabetes/Pre-Diabetes Comorbidity

Antigen-specific gamma-delta (γδ) T cells are important in exhibiting anti-mycobacterial immunity, but their role in latent tuberculosis (LTB) with diabetes mellitus (DM) or pre-DM (PDM) and non-DM comorbidities have not been studied. Thus, we have studied the baseline, mycobacterial (PPD, WCL), and positive control antigen-stimulated γδ T cells expressing Th1 (IFNγ, TNFα, IL-2) and Th17 (IL-17A, IL-17F, IL-22) cytokine as well as cytotoxic (perforin [PFN], granzyme [GZE B], granulysin [GNLSN]) and immune (GMCSF, PD-1, CD69) markers in LTB (DM, PDM, NDM) comorbidities by flow cytometry. In the unstimulated (UNS) condition, we did not observe any significant difference in the frequencies of γδ T cells expressing Th1 and Th17 cytokine, cytotoxic, and immune markers. In contrast, upon PPD antigen stimulation, the frequencies of γδ T cells expressing Th1 (IFNγ, TNFα) and Th17 (IL-17F, IL-22) cytokine, cytotoxic (PFN, GZE B, GNLSN), and immune (CD69) markers were significantly diminished in LTB DM and/or PDM individuals compared to LTB NDM individuals. Similarly, upon WCL antigen stimulation, the frequencies of γδ T cells expressing Th1 (TNFα) and Th17 (IL-17A, IL-22) cytokine, cytotoxic (PFN), and immune (PD-1, CD69) markers were significantly diminished in LTB DM and/or PDM individuals compared to LTB NDM individuals. Finally, upon P/I stimulation we did not observe any significant difference in the γδ T cell frequencies expressing cytokine, cytotoxic, and immune markers between the study populations. The culture supernatant levels of IFNγ, TNFα, and IL-17A cytokines were significantly increased in LTB DM and PDM after stimulation with Mtb antigens compared to LTB NDM individuals. Therefore, diminished γδ T cells expressing cytokine, cytotoxic, and other immune markers and elevated levels of cytokines in the supernatants is a characteristic feature of LTB PDM/DM co-morbidities.

Standardized astragalus extract for attenuation of the immunosuppression induced by strenuous physical exercise: randomized controlled trial

Background

This paper aimed to verify how a supplementation of rower’s diet with Astragalus Membranaceus Root (AMR) modulated their immune system response to maximal physical exertion.

Methods

The double-blind study included 18 members of the Polish Rowing Team assigned to the supplemented group (n = 10), and the placebo group (n = 8). The participants performed a 2000 m test on a rowing ergometer at the beginning and at the end of the six-week of intensive training camp during which the supplemented group received 500 mg of AMR. Blood samples were obtained prior to, 1 min after completing, and 24 h after the exertion test. The levels of interleukin 2 (IL2), interleukin 4 (IL4), interleukin 10 (IL10), interferon ɤ (IFN-ɣ), and lactic acid were determined. Subpopulations of T regulatory lymphocytes [CD4+/CD25+/CD127−] (Treg), cytotoxic lymphocytes [CD8+/TCRαβ+] (CTL), natural killer cells [CD3−/CD16+/CD56+] (NK), and TCRδγ-positive cells (Tδγ) were determined with flow cytometry.

Results

After the camp, the initial NK and Treg levels sustained at the baseline, while Tδγ counts increased relative to the levels in the placebo group. In the supplemented subgroup, a decrease in IL2 level in reaction to maximal exertion clearly deepened while the change in IL-2/IL-10 level induced by the recovery after this exertion clearly increased, relative to the changes in the placebo group.

Conclusions

AMR restored the immunological balance in strenuously trained athlets through a stabilization of NK and Treg cells with a positive trend in Tδγ towards Th1 response during restitution by cytokine IL2 modulation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12970-021-00425-5.

The effects of intradermal M. bovis and M. avium PPD test on immune-related mRNA and miRNA in dermal oedema exudates of water buffaloes (Bubalus bubalis)

Tuberculosis (TB) is a zoonotic disease primarily caused by pathogens belonging to the genus of Mycobacterium. Programs of control and eradication for bovine TB include a screening using single intradermal tuberculin (SIT) test with Mycobacterium bovis (M. bovis)-purified protein derivatives (PPD-B) single or concurrent with Mycobacterium avium (M. avium)-purified protein derivatives (PPD-A). This study aimed to determine the effects of intradermal PPD-B and PPD-A test on immune-related mRNA and microRNAs in dermal oedema exudates of water buffaloes (Bubalus bubalis). The investigation was carried out on RNA extracted from dermal oedema exudates of 36 animals, of which 24 were M. bovis positive (M. bovis+) and 12 M. avium positive (M. avium+). The lymphocyte polarization toward Th1, Th2, TReg, and Th17 lineages was addressed by measuring the abundance of the respective cytokines and transcription factors, namely TBET, STAT4, IFNγ, and IL1β for Th1; STAT5B, and IL4 for Th2; FOXP3 and IL10 for TReg; and RORC, STAT3, and IL17A for Th17. Due to the very low abundance of Th17-related genes, a digital PCR protocol was also applied. The abundance of microRNAs involved in the immune response against PPDs, including miR-122-5p, miR-148a-3p, miR30a, and miR-455-5p, was equally measured. Results showed that IFNγ (fold change = 2.54; p = 0.037) and miR-148a-3p (fold change = 2.54; p = 0.03) were upregulated in M. bovis+ as compared to M. avium+ samples. Our preliminary results supported the pivotal role of IFNγ in the local immune response related to PPD-B and highlighted the differential expression of miR-148a-3p, which downregulates the proinflammatory cytokines and the TLR4-mediated NF-κB activation, providing an anti-inflammation modulator in responses to mycobacterial infection.

Immune Cell Number, Phenotype, and Function in the Elderly with Sepsis

Sepsis is a form of life-threatening organ dysfunction caused by dysregulated host responses to an infection that can be partly attributed to immune dysfunction. Although sepsis affects patients of all ages, elderly individuals display increased susceptibility and mortality. This is partly due to immunosenescence, a decline in normal immune system function associated with physiological aging that affects almost all cell types in the innate and adaptive immune systems. In elderly patients with sepsis, these alterations in immune cells such as endothelial cells, neutrophils, monocytes, macrophages, natural killer cells, dendritic cells, T lymphocytes, and B lymphocytes, are largely responsible for their poor prognosis and increased mortality. Here, we review recent studies investigating the events affecting both innate and adaptive immune cells in elderly mice and patients with sepsis, including alterations in their number, phenotype, and function, to shed light on possible new therapeutic strategies.

Regulatory T cell targeting in cancer: Emerging strategies in immunotherapy

The adaptive immune system is modulated by an important subset of CD4⁺ T lymphocytes called Treg cells that function in maintaining immune homeostasis by preventing excessive immune activation. Both deficiency and overactivation of Treg cell function can result in disease pathology. While loss of Treg function can lead to autoimmunity, an overabundance of Treg activity can promote tumorigenesis. Blocking and/or depleting Tregs has emerged as a viable strategy to enhance antitumor immunity. A major limitation underlying the limited efficacy observed with Treg therapies in the clinic is lack of selective targeting, often attributed to concurrent depletion of antitumor effector T-cell populations. Novel approaches to improve the specificity of Treg targeting in the context of cancer include the use of T-cell receptor mimic antibodies, bispecific antibodies, and near-infrared photoimmunotherapy. Next-generation technology platforms and transcriptomic/computational-based screening methods have been recently developed to identify preferential Treg targets. Herein, we highlight key advancements and challenges pertaining to the development of novel Treg targeting cancer therapeutics and discuss ongoing clinical trials evaluating next-generation Treg therapies for solid tumors.

The Pivotal Role of Regulatory T Cells in the Regulation of Innate Immune Cells

The distinction between innate and adaptive immunity is one of the basic tenets of immunology. The co-operation between these two arms of the immune system is a major determinant of the resistance or susceptibility of the host following pathogen invasion. Hence, this interactive co-operation between cells of the innate and adaptive immunity is of significant interest to immunologists. The sub-population of CD4⁺ T cells with regulatory phenotype (regulatory T cells; Tregs), which constitute a part of the adaptive immune system, have been widely implicated in the regulation of the immune system and maintenance of immune homeostasis. In the last two decades, there has been an explosion in research describing the role of Tregs and their relevance in several immunopathologies ranging from inflammation to cancer. The majority of these studies focus on the role of Tregs on the cells of the adaptive immune system. Recently, there is significant interest in the role of Tregs on cells of the innate immune system. In this review, we examine the literature on the role of Tregs in immunology. Specifically, we focus on the emerging knowledge of Treg interaction with dendritic cells, macrophages, neutrophils, and γδ T cells. We highlight this interaction as an important link between innate and adaptive immune systems which also indicate the far-reaching role of Tregs in the regulation of immune responses and maintenance of self-tolerance and immune homeostasis.

IL-33 Protects Mice against DSS-Induced Chronic Colitis by Increasing Both Regulatory B Cell and Regulatory T Cell Responses as Well as Decreasing Th17 Cell Response

BACKGROUND

Previously, we have reported that IL-33 functioned as a protective modulator in dextran sulfate sodium- (DSS-) induced chronic colitis by suppressing Th17 cell response in colon lamina propria and IL-33 induced both regulatory B cells (Bregs) and regulatory T cells (Tregs) in mesenteric lymph nodes (MLNs) of mice with DSS-induced acute colitis. Moreover, we speculated that IL-33 would promote the Treg or Breg responses leading to the attenuation of DSS-induced chronic colitis. So, we investigated the role of IL-33 on Bregs and Tregs in the MLN of DSS-induced chronic colitis mice.

METHODS

IL-33 was administered by intraperitoneal injection to mice with DSS-induced chronic colitis. Clinical symptoms, colon length, and histological changes were determined. The production of cytokines was measured by ELISA. The T and B cell subsets were measured by flow cytometry. The expression of mRNA of transcription factors was measured by quantitative real-time PCR.

RESULTS

We show that IL-33 treatment increases both Breg and Treg responses in the MLN of mice with DSS-induced chronic colitis. Moreover, IL-33 treatment also decreases Th17 cell response in the MLN of mice with DSS-induced chronic colitis.

CONCLUSION

Our data provide clear evidence that IL-33 plays a protective role in DSS-induced chronic colitis, which is closely related to increasing Breg and Treg responses in the MLN of mice as well as suppressing Th17 cell responses.

Immunological characteristics of Mycobacterium tuberculosis subunit vaccines immunized through different routes

Tuberculosis is chronic infectious disease caused by Mycobacterium tuberculosis (M.tb) that is prevalent worldwide. Several specific antigens, such as Antigen 85B (Ag85B) and 6 kDa early secretory antigenic target (ESAT-6) protein of M.tb, are listed as some of the candidate subunit vaccines against M.tb. ESAT-6, as a virulent factor and differential gene in M.tb, shows insufficient immunogenicity in animal model. In order to investigate the ways to improve the immunogenicity of ESAT-6, we immunized ESAT-6 by subcutaneous and intramuscular routes with different adjuvants. We found that ESAT-6 immunized alone did not induce significant humoral immunity in both immunization routes. However, subcutaneous immunization of ESAT-6 plus incomplete Freund's adjuvant can induce a significant humoral immune response, enhanced proliferation and elevated secretion of IFN-γ from splenocytes. Intramuscular immunization of ESAT-6 plus adjuvant aluminum salt or poly(I:C) did not enhance humoral and cellular immune responses. Therefore, it is concluded that immunization of ESAT-6 subcutaneously plus incomplete Freund's adjuvant induces stronger humoral and cellular immune responses, which can be considered of ESAT-6 as a subunit vaccine in further research against tuberculosis.

Variegated Transcription of the WC1 Hybrid PRR/Co-Receptor Genes by Individual γδ T Cells and Correlation With Pathogen Responsiveness

γδ T cells have broad reactivity and actively participate in protective immunity against tumors and infectious disease-causing organisms. In γδ-high species such as ruminants and other artiodactyls many γδ T cells bear the lineage-specific markers known as WC1. WC1 molecules are scavenger receptors coded for by a multigenic array and are closely related to SCART found on murine γδ T cells and CD163 found on a variety of cells. We have previously shown that WC1 molecules are hybrid pattern recognition receptors thereby binding pathogens as well as signaling co-receptors for the γδ T cell receptor. WC1⁺ γδ T cells can be divided into two major subpopulations differentiated by the WC1 genes they express and the pathogens to which they respond. Therefore, we hypothesize that optimal γδ T cell responses are contingent on pathogen binding to WC1 molecules, especially since we have shown that silencing WC1 results in an inability of γδ T cells from primed animals to respond to the pathogen Leptospira, a model system we have employed extensively. Despite this knowledge about the crucial role WC1 plays in γδ T cell biology, the pattern of WC1 gene expression by individual γδ T cells was not known but is critical to devise methods to engage γδ T cells for responses to specific pathogens. To address this gap, we generated 78 γδ T cell clones. qRT-PCR evaluation showed that approximately 75% of the clones had one to three WC1 genes transcribed but up to six per cell occurred. The co-transcription of WC1 genes by clones showed many combinations and some WC1 genes were transcribed by both subpopulations although there were differences in the overall pattern of WC1 genes transcription. Despite this overlap, Leptospira-responsive WC1⁺ memory γδ T cell clones were shown to have a significantly higher propensity to express WC1 molecules that are known to bind to the pathogen.

Down-regulation of Helios Expression in Tregs from Patients with Hypertension

Regulatory T cells (Tregs) play a pivotal role in the pathological development of hypertension. Helios, a transcription factor from the Ikaros family, was recently reported to be a bona fide marker for natural Tregs or activated Tregs with suppression function, however, little has been known about its role in hypertension. This study was aimed to find whether Helios+ Tregs really play a vital role in hypertension. A total of 60 hypertension patients, and 46 normotension subjects were enrolled in this study. Frequencies of different Tregs subsets in peripheral blood were measured by flow cytometry. Plasma cytokine level was determined by ELISA. The mRNA expression of Foxp3 and Helios in purified CD4+ T cells was detected by RT-PCR. Proportion of CD4+Foxp3+Helios+ Tregs was decreased significantly in patients with hypertension (62.52%±1.18% vs. 71.89%±1.03%, P<0.01), and it was correlated with plasma level of IL-10 positively (a=0.505, P<0.05) and plasma level of IFN-gamma negatively (r=-0.551, P<0.05). The mRNA expression of Foxp3 (7.23±1.00 vs. 10.58±0.54, P<0.05) and Helios (8.47±0.95 vs. 15.52±2.0, P<0.05) was decreased in CD4+ T cells from patients with hypertension. Helios+ Tregs were decreased in patients with hypertension and may play a protective role in hypertension progression.

More significance of TB-IGRA except for the diagnose of tuberculosis

OBJECTIVE

Tuberculosis (TB)-interferon gamma release assay (IGRA) test has the characteristics of short time, high specificity, and high sensitivity, but it lacks the correlation research between TB-IGRA test results and body's immune cells, disease progression and prognosis, which is explored in this study.

DESIGN

A retrospective study was carried out on positive TB-IGRA patients who were infected with TB and diagnosed at our hospital from January 2014 to June 2015. The TB-IGRA, routine blood test, T-cell subgroup data were collected for statistical analysis.

RESULTS

TB-IGRA results were in positive proportion to the lymphocytes, CD4+ T cells and CD4+ CD28+ T cells, whereas negative to the Treg cells. Patient with unilateral pulmonary lesion had higher TB-IGRA than those with bilateral pulmonary lesions. After the stimulation of TB-specific antigen, the proportion of CD4+ IFN-γ+ and CD8+ IFN-γ+ T Tcells were both increased and the CD4+ IFN-γ+ T had positive correlation with the value of TB-IGRA.

CONCLUSIONS

IFN-γ was tested with TB-IGRA in patients with TB by the specific TB T cells and correlated with the lymphocytes, while the lymphocytes also closely related to the host's anti-TB immunity and disease outcome. Hence the result of TB-IGRA could reflect the specific anti-TB immunity ability of the host, disease progression and prognosis. This study further expands the application scope of TB-IGRA technology in the diagnosis of TB and lays a foundation for clinical practice to understand the immunity state of the patients with TB and the application of auxiliary clinical immunity regulators.

Sodium selenite ameliorates dextran sulfate sodium-induced chronic colitis in mice by decreasing Th1, Th17, and γδT and increasing CD4(+)CD25(+) regulatory T-cell responses

AIM

To assess the effect of sodium selenite on the severity of dextran sulfate sodium (DSS)-induced colitis in C57BL/6 mice.

METHODS

Mice were randomly divided into four groups (n = 10/group): normal group, selenium (Se) group, chronic colitis group, and Se + chronic colitis group. The mice were sacrificed on day 26. Survival rates, clinical symptoms, colon length, and histological changes were determined. The percentages and absolute numbers of immune system cells in the lamina propria lymphocytes (LPL) of the colon, the expression of mRNA in colon tissue, and the concentrations of Th1, Th17, and Treg cytokines in LPL from the large intestine, were measured.

RESULTS

Se significantly ameliorated the symptoms of colitis and histological injury (P < 0.05 each), increasing the proportions of neutrophils and CD4⁺ CD25⁺ T cells (P < 0.05 each) and decreasing the proportions of γδT cells, CD4⁺, CD4⁺CD44⁺, and CD4⁺ CD69⁺ T cells in LPL (P < 0.05 each). Moreover, Se reduced the expression of IL-6, IFN-γ, IL-17A, IL-21, T-bet, and RORγt (P < 0.05 each), but enhanced the expression of IL-10 and Foxp3 (P < 0.05 each).

CONCLUSION

These results suggest that Se protects against DSS-induced chronic colitis perhaps by increasing the number of CD4(+)CD25(+) Tregs that suppress the secretion of proinflammatory cytokines and populations of Th1, Th17, and γδT cells.

Squamous Cell Tumors Recruit γδ T Cells Producing either IL17 or IFNγ Depending on the Tumor Stage

The identification of reciprocal interactions between tumor-infiltrating immune cells and the microenviroment may help us understand mechanisms of tumor growth inhibition or progression. We have assessed the frequencies of tumor-infiltrating and circulating γδ T cells and regulatory T cells (Treg) from 47 patients with squamous cell carcinoma (SCC), to determine if they correlated with progression or survival. Vδ1 T cells infiltrated SSC tissue to a greater extent than normal skin, but SCC patients and healthy subjects had similar amounts circulating. However, Vδ2 T cells were present at higher frequencies in circulation than in the tissue of either cancer patients or healthy donors. Tregs were decreased in the peripheral blood of SCC patients, but were significantly increased in the tumor compartment of these patients. Tumor-infiltrating γδ T cells preferentially showed an effector memory phenotype and made either IL17 or IFNγ depending on the tumor stage, whereas circulating γδ T cells of SCC patients preferentially made IFNγ. Different cell types in the tumor microenvironment produced chemokines that could recruit circulating γδ T cells to the tumor site and other cytokines that could reprogram γδ T cells to produce IL17. These findings suggest the possibility that γδ T cells in SCC are recruited from the periphery and their features are then affected by the tumor microenvironment. Elevated frequencies of infiltrating Vδ2 T cells and Tregs differently correlated with early and advanced tumor stages, respectively. Our results provide insights into the functions of tumor-infiltrating γδ T cells and define potential tools for tumor immunotherapy. Cancer Immunol Res; 5(5); 397-407. ©2017 AACR.

Comparing TSPOT assay results between an Elispot reader and manual counts

BACKGROUND

The interferon gamma release assay, TSPOT.TB (TSPOT) can be read by several methodologies, including an Elispot reader or manually by technician. We compared the results from these two counting methods.

METHODS

Automated and manual TSPOT results among 2481 United States health care workers were compared. Cohen's kappa coefficient was used to determine the inter-rater agreement. Univariate and multiple logistic regression were used to investigate selected variable contributions.

RESULTS

No prognostic factors were associated with agreement of TSPOT results between counting methods. Agreement between TSPOT results were 92.3%, 89.5%, 93.0%, and 93.1% at baseline, and at follow-up at 6, 12, and 18 months, respectively. The inter-rater agreement for all test results was good (kappa = 0.71). There was a significant difference between individual technicians kappa coefficients (p < 0.001), but no significant increase in agreement over time for technicians (p = 0.394).

CONCLUSION

Commercial Elispot readers and manual counts have good agreement of TSPOT results in a low TB burden setting. Levels of agreement differed between individual technicians and automated reader from moderate to very good, indicating borderline results may be misinterpreted due to inter-rater variability. With no latent tuberculosis infection (LTBI) gold standard, it cannot be determined if one TSPOT reading method is better than another.

Antigen-specific human NKT cells from tuberculosis patients produce IL-21 to help B cells for the production of immunoglobulins

Natural killer T (NKT) cells from mouse and human play an important role in the immune responses against Mycobacterium tuberculosis. However, the function of CD3(+)TCRvβ11(+) NKT cells at the local site of M. tuberculosis infection remains poorly defined. In the present study, we found that after stimulation with M. tuberculosis antigens, NKT cells isolated from tuberculosis (TB) pleural fluid mononuclear cells (PFMCs) produced IL-21 and other cytokines including IFN-γ, TNF-α, IL-2 and IL-17. IL-21-expressing NKT cells in PFMCs displayed effector memory phenotype, expressing CD45RO(high)CD62L(low)CCR7(low). Moreover, NKT cells expressed high levels of CXCR5 and all of IL-21-expressing NKT cells co-expressed CXCR5. The frequency of BCL-6-expression was higher in IL-21-expressing but not in non-IL-21-expressing CD3(+)TCRvβ11(+) NKT cells. Sorted CD3(+)TCRvβ11(+) NKT cells from PFMCs produced IFN-γ and IL-21 after stimulation, which expressed CD40L. Importantly, CD3(+)TCRvβ11(+) NKT cells provided help to B cells for the production of IgG and IgA. Taken together, our data demonstrate that CD3(+)TCRvβ11(+) NKT cells from a local site of M. tuberculosis infection produce IL-21, express CXCR5 and CD40L, help B cells to secrete IgG and IgA, and may participate in local immune responses against M. tuberculosis infection.

Effective expansion of forkhead box P3⁺ regulatory T cells via early secreted antigenic target 6 and antigen 85 complex B from Mycobacterium tuberculosis

The expansion of CD4+ CD25+ forkhead box (FOX)P3+ regulatory T (Treg) cells has been observed in patients with Mycobacterium (M.) tuberculosis; however, the mechanism of expansion remains to be elucidated. The aim of the present study was to examine the role of the early secreted antigenic target 6(ESAT‑6) and antigen 85 complex B (Ag85B) from M. tuberculosis on Treg cell expansion. To investigate the sensitivity of peripheral blood cultures to the M. tuberculosis ESAT‑6 and Ag85B antigens, the proportion of circulating CD4+ CD25+ FOXP3+ Treg cells was determined using flow cytometry and the levels of FOXP3 mRNA were determined using reverse transcription quantitative polymerase chain reaction. The mRNA levels of FOXP3 and the proportion of circulating CD4+ CD25+ FOXP3+ Treg cells were increased in multiplicitous drug‑resistant tuberculosis patients compared with those in healthy controls and patients with latent tuberculosis (TB) infection (LTBI) (P<0.001). The mycobacterial antigens ESAT‑6 and Ag85B increased the expansion of the CD4+ CD25+ FOXP3+ Treg cells and the mRNA levels of FOXP3 in healthy controls and LTBI patients compared with the effect of Bacillus Calmette‑Guerin (P<0.05). Additionally, the mRNA levels of FOXP3 were elevated in the LTBI patients following stimulations with the mycobacterial antigens (P=0.012). Therefore, the M. tuberculosis antigens ESAT‑6 and Ag85B induced CD4+ CD25+ FOXP3+ Treg‑cell expansion, particularly in patients with LTBI. These findings indicated that CD4+ CD25+ FOXP3+ Treg cells may have a primary role in the failure of the host immune system to eradicate M. tuberculosis.

Phenotyping of peripheral blood mononuclear cells of patients with advanced heavily pre-treated adenocarcinoma of the stomach and gastro-esophageal junction

Immunotherapeutic approaches are emerging as promising new treatment options for patients with solid cancers. The host immune system in cancer patients is dysfunctional due to a number of reasons. The level of immunosuppression is variable at the time of diagnosis and depends on the particular cancer entity, stage, and prior anti-cancer therapies. For many cancer entities, the immune alterations of the respective patient population have not been further characterized even though a patient's immunophenotype may be prognostic for the course of the disease or predictive for clinical/biological response to immunotherapy. In this study, we used flow cytometry to determine the phenotype of peripheral blood mononuclear cells (PBMCs) from 30 patients with heavily pre-treated, advanced adenocarcinoma of the stomach and gastro-esophageal junction. The frequencies and activation status of relevant immune effector populations were determined in PBMCs and compared to those of healthy individuals. This report provides comprehensive immune phenotyping data of a patient population with a high medical need.

Anti-tuberculosis treatment enhances the production of IL-22 through reducing the frequencies of regulatory B cell

IL-22 has been suggested to play an important role in immune response against Mycobacterium tuberculosis infection. However, the exact role of IL-22 in human tuberculosis (TB) infection remains unclear and the regulatory mechanism of IL-22 response in human TB is unknown. In this study, we observed that successful anti-tuberculosis treatment induced an enhanced and sustained M. tuberculosis antigen-specific IL-22 response, correlated with the decrease of the frequencies of CD19(+)CD5(+)CD1d(+) regulatory B cells. We also found that depletion of CD19(+) B cells significantly enhanced M. tuberculosis antigen-specific IL-22 production by peripheral blood mononuclear cells. More importantly, we observed that purified CD19(+) B cells, and more efficiently, CD19(+)CD5(+)CD1d(+) regulatory B cells, suppressed IL-22 production. In summary, we showed here for the first time that effective anti-tuberculosis treatment restores M. tuberculosis antigen-specific IL-22 response through a novel mechanism by reducing the frequencies of CD19(+)CD5(+)CD1d(+) regulatory B cells in human TB.

CD45RA-Foxp3high but not CD45RA+Foxp3low suppressive T regulatory cells increased in the peripheral circulation of patients with head and neck squamous cell carcinoma and correlated with tumor progression

Background

T regulatory cells (Tregs) contribute to the progression of head and neck squamous cell carcinoma (HNSCC) by suppressing antitumor immunity. However, little is known regarding the functional heterogeneity of Tregs in HNSCC patients.

Methods

Using multicolor flow cytometry, the frequency of three Treg subsets, separated on the basis of CD45RA and Foxp3, from the peripheral circulation of newly-presenting HNSCC patients (19 oral cavity squamous cell carcinoma, 20 hypopharyngeal squamous cell carcinoma, 18 nasopharyngeal squamous cell carcinoma, 19 oropharyngeal squamous cell carcinoma, and 36 laryngeal squamous cell carcinoma) were assessed with regard to 31 healthy donors and clinicopathological features. Moreover, the functional capacity of each Treg subsets was evaluated based on CD45RA and CD25 expression.

Results

The frequency of Tregs in the peripheral circulation of HNSCC patients as a whole cohort was higher than in healthy donors (P < 0.0001). However, the frequency of Tregs was similar between patients with oral cavity squamous cell carcinoma and healthy donors (P = 0.269). Further dividing Tregs into three subsets based on Foxp3 and CD45RA expression revealed that the frequency of CD45RA^-Foxp3^high Tregs and CD45RA^-Foxp3^lowCD4⁺ T cells in patients with HNSCC developing from different subsites was higher than in healthy donors (P < 0.0001, P < 0.0001), whereas the frequency of CD45RA⁺Foxp3^low Tregs was lower than in healthy donors (P < 0.0001). Functionally study revealed that CD45RA^-CD25⁺⁺⁺ Tregs significantly inhibit the proliferation of CD4⁺CD25^- T cells (P < 0.001) and secrete lower levels of cytokines (P < 0.01) compared with CD45RA^-CD25⁺⁺CD4⁺ T cells. Importantly, the frequency of CD45RA^-Foxp3^high Tregs positively correlate with tumor stage (P < 0.0001) and nodal status (P < 0.0001).

Conclusions

CD45RA^-Foxp3^high Tregs increase in the peripheral circulation of HNSCC patients, and correlate with tumor stage and nodal status; suggesting a role in tumor progression which may be manipulated by future immunotherapy.

Tumor-activated TCRγδ⁺ T cells from gastric cancer patients induce the antitumor immune response of TCRαβ⁺ T cells via their antigen-presenting cell-like effects

Human γδ T cells display the principal characteristics of professional antigen-presenting cells (APCs), in addition to playing a vital role in immunity through cytokine secretion and their cytotoxic activity. However, it is not clear whether γδ T cells perform APC-like functions under pathological conditions. In this study, we showed that, in contrast to peripheral-derived γδ T cells directly isolated from PBMCs of gastric cancer patients, tumor-activated γδ T cells not only killed tumor cells efficiently but also strongly induced primary CD4⁺ and CD8⁺   αβ T cells proliferation and differentiation. More importantly, they abrogated the immunosuppression induced by CD4⁺CD25⁺ Treg cells and induced the cytotoxic function of CD8⁺   αβ T cells from patients with gastric cancer. In conclusion, tumor-activated γδ T cells can induce adaptive immune responses through their APC-like functions, and these cells may be a potentially useful tool in the development of tumor vaccines and immunotherapy.

How to avoid the impact of environmental mycobacteria towards the efficacy of BCG vaccination against tuberculosis?

Bacillus Calmette-Guérin (BCG) remains the only widely used vaccine against tuberculosis (TB). Consistent efficacy has been proved in infants but not in adults from developing countries. Epidemiological and experimental studies have pointed out that, prior exposure to prevailing environmental mycobacteria could be responsible for the poor efficacy of BCG as an anti-TB vaccine in adults living in developing countries. Sensitization by environmental mycobacteria may down-modulate the immunologic behavior of BCG on the one hand and may mask its efficacy on the other hand. Some of the important deciding factors for poor efficacy of BCG, due to exposure of the subjects to prevailing environmental mycobacteria, are thought to be (i) Life stage: neonatus versus adolescence; (ii) shared antigens between prevailing environmental mycobacteria and BCG; and (iii) generation of cross-reactive T-regulatory cells against environmental mycobacteria and BCG. In this communication, some novel strategies have been discussed for countering the down modulating impact of environmental mycobacteria towards performance of BCG as an anti-TB vaccine.

Sepsis-induced immunosuppression: from cellular dysfunctions to immunotherapy

Sepsis - which is a severe life-threatening infection with organ dysfunction - initiates a complex interplay of host pro-inflammatory and anti-inflammatory processes. Sepsis can be considered a race to the death between the pathogens and the host immune system, and it is the proper balance between the often competing pro- and anti-inflammatory pathways that determines the fate of the individual. Although the field of sepsis research has witnessed the failure of many highly touted clinical trials, a better understanding of the pathophysiological basis of the disorder and the mechanisms responsible for the associated pro- and anti-inflammatory responses provides a novel approach for treating this highly lethal condition. Biomarker-guided immunotherapy that is administered to patients at the proper immune phase of sepsis is potentially a major advance in the treatment of sepsis and in the field of infectious disease.

The functional impairment of HCC-infiltrating γδ T cells, partially mediated by regulatory T cells in a TGFβ- and IL-10-dependent manner

BACKGROUND & AIMS

The immunosuppressive network within the tumor microenvironment is one of the major obstacles to the success of cancer immunotherapy. γδ T cells are attractive effectors for cancer immunotherapy. Nevertheless, the promising anti-tumor effect in vitro is partially if not totally mitigated in vivo. Thus, understanding the immune status of tumor-infiltrating γδ T cells is essential for orchestrating effective immunotherapy strategies. In this study, we have investigated the immunophenotype and function of γδ T cells in hepatocellular carcinoma (HCC) patients.

METHODS

The phenotype of γδ T cells in peripheral blood, and peritumoral and tumoral tissues of HCC patients (n=61) was characterized by flow cytometry. Functional analysis of the HCC-infiltrating γδ T cells was conducted directly after γδ T cell isolation.

RESULTS

The infiltration of γδ T cells in tumoral tissues was significantly reduced compared to paired peritumoral tissues. Impairment in degranulation of the granule pathway and downregulation of IFN-γ secretion were also demonstrated in HCC-infiltrating γδ T cells, which was in agreement with the results of gene microarray analysis, and further strengthened by the compromised specific cytotoxicity and IFN-γ secretion in vitro. Moreover, isolated HCC-infiltrating CD4(+)CD25(+) regulatory T cells (Treg cells) directly suppressed the cytotoxic function and IFN-γ secretion of γδ T cells in a TGFβ- and IL-10-dependent manner.

CONCLUSIONS

The effector function of γδ T cells was substantially impaired in HCC, which is partially mediated by Treg cells. We propose a new mechanism by which immune privilege develops within the tumor milieu.

Subpopulations of helper T lymphocytes in tuberculous pleurisy

Although it is curable, tuberculosis continues to be is a major global public health problem, especially in developing countries. Tuberculous pleural effusion (TPE) is one of the most common forms of extrapulmonary tuberculosis. It has been well documented that CD4(+) T lymphocytes are dominant leukocytes present in TPE. Traditionally, CD4(+) T cells have been classified into two functionally distinct subsets, helper T-cell type 1 (Th1) and Th2 cells, based on their cytokine production profiles. Recently, regulatory T cells, Th17 cells, Th9 cells, and Th22 cells have been added to the 'portfolio' of Th cells. In this review, we summarize recent findings regarding the phenotypic characteristics of the above Th cells, the mechanisms of differentiation and recruitment of Th cells into pleural space, and the immune regulation of Th cells in TPE environment. We also describe the interplay between different Th cells, as well as between Th cells and other type of cells, such as pleural mesothelial cells in TPE. Further studies should be directed at identifying the mediators and mechanisms involved in the immunoregulatory properties of pleural Th cells in tuberculosis infection.

Roles of γδ T cells in the pathogenesis of autoimmune diseases

γδ T cells are a minor population of T cells that express the TCR γδ chains, mainly distributed in the mucosal and epithelial tissue and accounting for less than 5% of the total T cells in the peripheral blood. By bridging innate and adaptive immunity, γδ T cells play important roles in the anti-infection, antitumor, and autoimmune responses. Previous research on γδ T cells was primarily concentrated on infectious diseases and tumors, whereas their functions in autoimmune diseases attracted much attention. In this paper, we summarized the various functions of γδ T cells in two prototypical autoimmune connective tissue diseases, that is, SLE and RA, elaborating on their antigen-presenting capacity, secretion of proinflammatory cytokines, immunomodulatory effects, and auxiliary function for B cells, which contribute to overproduction of proinflammatory cytokines and pathogenic autoantibodies, ultimately leading to the onset of these autoimmune diseases. Elucidation of the roles of γδ T cells in autoimmune diseases is not only conducive to in-depth understanding of the pathogenesis of these diseases, but also beneficial in providing theoretical support for the development of γδ T-cell-targeted therapy.

Regulatory functions of γδ T cells

γδ T cells account for approximately 5% of peripheral blood T cells but are more abundant in mucosal tissue. Based on the recognized ligands and their general lack of MHC restriction, γδ T cells are considered as unconventional T cells that link innate and adaptive immunity. γδ T cells produce a diverse range of cytokines, exert cytotoxic effector function, can act as antigen-presenting cells, and display regulatory activity. Here we review the current knowledge on the regulatory functions of murine and human γδ T cells. Some γδ T cells produce inhibitory cytokines such as transforming growth factor-β but γδ T cells can utilize additional regulatory mechanisms. By subverting regulatory T cells (Treg) through induction of Treg apoptosis or cytokine-dependent reversal of Treg activity, however, γδ T cells can also enhance effector T cell activity and thereby contribute to autoimmunity. A more precise understanding of the plasticity of regulatory γδ T cells is required to specifically identify strategies for intentional modulation of their beneficial or detrimental regulatory activity.

Identification of a new tuberculosis antigen recognized by γδ T cell receptor

The immune protection initiated by γδ T cells plays an important role in mycobacterial infection. The γδ T cells activated by Mycobacterium tuberculosis-derived nonpeptidic, phosphorylated biometabolites (phosphoantigens) provide only partial immune protection against mycobacterium, while evidence has suggested that protein antigen-activated γδ T cells elicit effective protective immune responses. To date, only a few distinct mycobacterial protein antigens have been identified. In the present study, we screened protein antigens recognized by γδ T cells using cells transfected with the predominant pulmonary tuberculosis γδ T cell receptor (TCR) CDR3 fragment. We identified two peptides, TP1 and TP2, which not only bind to the pulmonary tuberculosis predominant γδ TCR but also effectively activate γδ T cells isolated from pulmonary tuberculosis patients. Moreover, 1-deoxy-d-xylulose 5-phosphate synthase 2 (DXS2), the TP1-matched mycobacterial protein, was confirmed as a ligand for the γδ TCR and was found to activate γδ T cells from pulmonary tuberculosis patients. The extracellular region (extracellular peptide [EP]) of Rv2272, a TP2-matched mycobacterial transmembrane protein, was also shown to activate γδ T cells from pulmonary tuberculosis patients. Both DXS2- and EP-expanded γδ T cells from pulmonary tuberculosis patients could secrete gamma interferon (IFN-γ) and monocyte chemoattractant protein 1 (MCP-1), which play important roles in mediating cytotoxicity against mycobacterium and stimulating monocyte chemotaxis toward the site of infection. In conclusion, our study identified novel mycobacterial protein antigens recognized by γδ TCR cells that could be candidates for the development of vaccines or adjuvants against mycobacterium infection.

Expression of regulatory receptors on γδ T cells and their cytokine production in Behcet's disease

INTRODUCTION

Behcet's disease (BD) is a multi-systemic disorder with muco-cutaneous, ocular, arthritic, vascular or central nervous system involvement. The role of γδ T cells is implicated in BD. The activation status of γδ T cells and their cytokine secretion against phosphoantigens are evaluated in BD.

METHODS

NKG2A, NKG2C, NKG2D, CD16 and CCR7 molecules on γδ T cells were analyzed in 70 BD, 27 tuberculosis (TB) patients and 26 healthy controls (HC). Peripheral γδ T cells were expanded with a phosphoantigen (BrHPP) and IL-2, restimulated with BrHPP and a TLR3 ligand, and cytokine production was measured.

RESULTS

γδ T cells were not increased in both BD and TB patients, but the proportions of TCRVδ2+ T cells were lower (58.9 and 50.7 vs. 71.7%, P=0.04 and P=0.005) compared to HC. Higher proportion of TCRVδ2+ T cells were CD16+ (26.2 and 33.9 vs. 16.6%, P=0.02 and P=0.001) and CCR7- (32.2 and 27.9 vs. 17.7%, P<0.0001 and P=0.014) in BD and TB patients compared to HC. NKG2C+ γδ+ T cells were relatively increased (0.5 and 0.6 vs. 0.3%, P=0.008 and 0.018), whereas NKG2D positivity was decreased in patients with BD and TB (77.7 and 75.8 vs. 87.5%, P=0.001 and 0.004). Expansion capacity of γδ T cells in BD and TB as well as production of IL-13, IFN-γ, granulocyte monocyte colony stimulating factor (GM-CSF), TNF-α, CCL4 and CCL5 in BD was lower compared to HC, when restimulated by TLR3 ligand and BrHPP.

CONCLUSION

The changes on γδ T cells of BD as well as TB patients implicate that γδ T cells have already been exposed to regulatory effects, which changed their activity. Lower cytokine response of γδ T cells implicates down modulation of these cells in BD.

Diversity of γδ T-cell antigens

In the last two decades, it has become clear that γδ T cells recognize a diverse array of antigens including self and foreign, large and small, and peptidic and non-peptidic molecules. In this respect, γδ antigens as a whole resemble more the antigens recognized by antibodies than those recognized by αβ T cells. Because of this antigenic diversity, no single mechanism-such as the major histocompatibility complex (MHC) restriction of αβ T cells-is likely to provide a basis for all observed T-cell antigen receptor (TCR)-dependent γδ T-cell responses. Furthermore, available evidence suggests that many individual γδ T cells are poly-specific, probably using different modes of ligand recognition in their responses to unrelated antigens. While posing a unique challenge in the maintenance of self-tolerance, this broad reactivity pattern might enable multiple overlapping uses of γδ T-cell populations, and thus generate a more efficient immune response.

HIV Gag-specific immune response mediated by double negative (CD3(+)CD4(-)CD8(-)) T cells in HIV-exposed seronegative individuals

Double negative (DN) T cells are CD3(+), CD4(-), CD8(-) cells with either T-cell receptors (TCR) αβ or TCR γδ whose importance on protection against HIV infection is unknown. Since HIV-exposed seronegative individuals correspond to an ideal group in whom correlates of protection are expected, the role of these cells was studied in 13 HIV-serodiscordant couples in a stable relationship and reporting unprotected sexual intercourses. HIV-specific immune responses mediated by DN T-cells were evaluated by measuring intracellular IFNγ and MIP1β (CCL4) production in response to HIV-Gag peptides. Thirty-five healthy controls not exposed to HIV were tested similarly and used to define a threshold for positive responses. Interestingly, Gag-specific DN T-cell responses were found in 3/13 (23%) HIV-exposed seronegative individuals (Group A), involving both DN/αβ(+) and DN/γδ(+) T-cells through MIP1β and IFNγ production. 4/13 (30%) of partners infected with HIV (Group B) also showed Gag-specific responses but were mediated exclusively by DN/γδ(+) T-cells, mainly through IFNγ production. DN T-cells in Group A individuals can display differential HIV-specific immune responses, which might contribute to the low susceptibility to infection with HIV shown by individuals in Group A.

Homeostasis and function of regulatory T cells in HIV/SIV infection

Regulatory T cells (Tregs) play a pivotal role in the maintenance of tolerance as well as in the control of immune activation, particularly during chronic infections. In the setting of HIV infection, the majority of studies have reported an increase in Treg frequency but a decrease in absolute number in all immune compartments of HIV-infected individuals. Several nonexclusive mechanisms have been postulated to explain this preferential Treg accumulation, including peripheral survival, increased proliferation, increased peripheral conversion, and tissue redistribution. The role played by Tregs during HIV infection is still poorly understood, as two opposing hypotheses have been proposed. A detrimental role of Tregs during HIV infection was suggested based on the evidence that Tregs suppress virus-specific immune responses. Conversely, Tregs could be beneficial by limiting immune activation, thus controlling the availability of HIV targets as well as preventing immune-based pathologies. Despite the technical difficulties, getting a better understanding of the mechanisms regulating Treg dynamics remains important, as it will help determine whether we can successfully manipulate Treg function or number to the advantage of the infected host. The aim of this review is thus to discuss the recent findings on Treg homeostasis and function in the setting of HIV infection.

Regulatory T cells exhibit decreased proliferation but enhanced suppression after pulsing with sirolimus

Although regulatory T cells (Tregs) suppress allo-immunity, difficulties in their large-scale production and in maintaining their suppressive function after expansion have thus far limited their clinical applicability. Here we have used our nonhuman primate model to demonstrate that significant ex vivo Treg expansion with potent suppressive capacity can be achieved and that Treg suppressive capacity can be further enhanced by their exposure to a short pulse of sirolimus. Both unpulsed and sirolimus-pulsed Tregs (SPTs) are capable of inhibiting proliferation of multiple T cell subpopulations, including CD4(+) and CD8(+) T cells, as well as antigen-experienced CD28(+) CD95(+) memory and CD28(-) CD95(+) effector subpopulations. We further show that Tregs can be combined in vitro with CTLA4-Ig (belatacept) to lead to enhanced inhibition of allo-proliferation. SPTs undergo less proliferation in a mixed lymphocyte reaction (MLR) when compared with unpulsed Tregs, suggesting that Treg-mediated suppression may be inversely related to their proliferative capacity. SPTs also display increased expression of CD25 and CTLA4, implicating signaling through these molecules in their enhanced function. Our results suggest that the creation of SPTs may provide a novel avenue to enhance Treg-based suppression of allo-immunity, in a manner amenable to large-scale ex vivo expansion and combinatorial therapy with novel, costimulation blockade-based immunosuppression strategies.

Nocardia brasiliensis induces an immunosuppressive microenvironment that favors chronic infection in BALB/c mice

Nocardia brasiliensis is an intracellular microorganism and the most common etiologic agent of actinomycetoma in the Americas. Several intracellular pathogens induce an immunosuppressive microenvironment through increases in CD4+ Foxp3+ regulatory T cells (Treg), thus downregulating other T-cell subpopulations and assuring survival in the host. In this study, we determined whether N. brasiliensis modulates T-lymphocyte responses and their related cytokine profiles in a murine experimental model. We also examined the relationship between N. brasiliensis immunomodulation and pathogenesis and bacterial survival. In early infection, Th17/Tc17 cells were increased at day 3 (P < 0.05) in footpad tissue and spleen. Treg subpopulations peaked at days 7 and 15 (P < 0.01) in the footpad and spleen, respectively. Transforming growth factor β1 (TGF-β1) and interleuki-10 (IL-10) are cytokines known for their immunosuppressive effects. During early and chronic infections, these cytokines were elevated with increased TGF-β1 levels from days 3 to 30 (P < 0.01) and sustained IL-10 expression throughout infection compared to uninfected mice. IL-6 production was increased at day 3 (P < 0.01), whereas gamma interferon (IFN-γ), IL-17A, and IL-23 levels were highest at day 15 postinfection (P < 0.01) when a decrease in the bacterial load (>1 log) was also observed (P < 0.05). After these changes, at 30 to 60 days postinfection, IFN-γ production was decreased, whereas the expression of anti-inflammatory cytokines and the bacterial load again increased (P < 0.05). The increment in Treg cells and the related cytokine profile correlated with reduced inflammation at day 15 (P < 0.05) in the footpad. We conclude that N. brasiliensis modulates the immune system to induce an immunosuppressive microenvironment that benefits its survival during the chronic stage of infection.

Porcine regulatory T cells: mechanisms and T-cell targets of suppression

Tregs are known for their suppressive capacity on various immune reactions. In swine, existence as well as suppressive activity of Foxp3(+) Tregs could be demonstrated but detailed functional investigations are lacking. Therefore, we analysed the functional properties of porcine Tregs. We observed that besides TCR stimulation Tregs require IL-2 for activation. Furthermore, we investigated the following mechanisms of suppression: (i) cell-cell contact dependency, (ii) production of soluble suppressive factors and (iii) competition for growth factors. Our experiments revealed that suppression by porcine Tregs is abrogated by blocking cell-cell contact or by supplementing excessive amounts of IL-2. Additionally it could be shown that porcine Tregs produce immunosuppressive IL-10. Thereby, we demonstrated that porcine Tregs can use all main mechanisms of suppression mentioned above. Further investigations on the suppressive activity of Tregs using CFSE proliferation assays demonstrated that suppression affects T-helper cells as well as cytotoxic T lymphocytes and TCR-γδ T cells.

Novel biomarkers distinguishing active tuberculosis from latent infection identified by gene expression profile of peripheral blood mononuclear cells

Background

Humans infected with Mycobacterium tuberculosis (MTB) can delete the pathogen or otherwise become latent infection or active disease. However, the factors influencing the pathogen clearance and disease progression from latent infection are poorly understood. This study attempted to use a genome-wide transcriptome approach to identify immune factors associated with MTB infection and novel biomarkers that can distinguish active disease from latent infection.

Methodology/Principal Findings

Using microarray analysis, we comprehensively determined the transcriptional difference in purified protein derivative (PPD) stimulated peripheral blood mononuclear cells (PBMCs) in 12 individuals divided into three groups: TB patients (TB), latent TB infection individuals (LTBI) and healthy controls (HC) (n = 4 per group). A transcriptional profiling of 506 differentially expressed genes could correctly group study individuals into three clusters. Moreover, 55- and 229-transcript signatures for tuberculosis infection (TB&LTBI) and active disease (TB) were identified, respectively. The validation study by quantitative real-time PCR (qPCR) performed in 83 individuals confirmed the expression patterns of 81% of the microarray identified genes. Decision tree analysis indicated that three genes of CXCL10, ATP10A and TLR6 could differentiate TB from LTBI subjects. Additional validation was performed to assess the diagnostic ability of the three biomarkers within 36 subjects, which yielded a sensitivity of 71% and specificity of 89%.

Conclusions/Significance

The transcription profiles of PBMCs induced by PPD identified distinctive gene expression patterns associated with different infectious status and provided new insights into human immune responses to MTB. Furthermore, this study indicated that a combination of CXCL10, ATP10A and TLR6 could be used as novel biomarkers for the discrimination of TB from LTBI.