Polarized helper T cells in tubercular pleural effusion: phenotypic identity and selective recruitment

Reanalysis and validation of the transcriptional pleural fluid signature in pleural tuberculosis

Introduction

Pleural tuberculosis (PlTB), the most common site of extrapulmonary TB, is characterized by a paucibacillary nature and a compartmentalized inflammatory response in the pleural cavity, both of which make diagnosis and management extremely challenging. Although transcriptional signatures for pulmonary TB have already been described, data obtained by using this approach for extrapulmonary tuberculosis and, specifically, for pleural tuberculosis are scarce and heterogeneous. In the present study, a set of candidate genes previously described in pulmonary TB was evaluated to identify and validate a transcriptional signature in clinical samples from a Brazilian cohort of PlTB patients and those with other exudative causes of pleural effusion.

Methods

As a first step, target genes were selected by a random forest algorithm with recursive feature elimination (RFE) from public microarray datasets. Then, peripheral blood (PB) and pleural fluid (PF) samples from recruited patients presenting exudative pleural effusion were collected during the thoracentesis procedure. Transcriptional analysis of the selected top 10 genes was performed by quantitative RT-PCR (RT-qPCR).

Results

Reanalysis of the public datasets identified a set of candidate genes (CARD17, BHLHE40, FCGR1A, BATF2, STAT1, BTN3A1, ANKRD22, C1QB, GBP2, and SEPTIN4) that demonstrated a global accuracy of 89.5% in discriminating pulmonary TB cases from other respiratory diseases. Our validation cohort consisted of PlTB (n = 35) patients and non-TB (n = 34) ones. The gene expressions of CARD17, GBP2, and C1QB in PF at diagnosis were significantly different between the two (PlTB and non-TB) groups (p < 0.0001). It was observed that the gene expressions of CARD17 and GBP2 were higher in PlTB PF than in non-TB patients. C1QB showed the opposite behavior, being higher in the non-TB PF. After anti-TB therapy, however, GBP2 gene expression was significantly reduced in PlTB patients (p < 0.001). Finally, the accuracy of the three above-cited highlighted genes in the PF was analyzed, showing AUCs of 91%, 90%, and 85%, respectively. GBP2 was above 80% (sensitivity = 0.89/specificity = 0.81), and CARD17 showed significant specificity (Se = 0.69/Sp = 0.95) in its capacity to discriminate the groups.

Conclusion

CARD17, GBP2, and C1QB showed promise in discriminating PlTB from other causes of exudative pleural effusion by providing accurate diagnoses, thus accelerating the initiation of anti-TB therapy.

The tuberculous pleural effusion

Pleural tuberculosis (TB) is a common entity with similar epidemiological characteristics to pulmonary TB. It represents a spectrum of disease that can variably self-resolve or progress to TB empyema with severe sequelae such as chronic fibrothorax or empyema necessitans. Coexistence of and progression to pulmonary TB is high. Diagnosis is challenging, as pleural TB is paucibacillary in most cases, but every effort should be made to obtain microbiological diagnosis, especially where drug resistance is suspected. Much attention has been focussed on adjunctive investigations to support diagnosis, but clinicians must be aware that apparent diagnostic accuracy is affected both by the underlying TB prevalence in the population, and by the diagnostic standard against which the specified investigation is being evaluated. Pharmacological treatment of pleural TB is similar to that of pulmonary TB, but penetration of the pleural space may be suboptimal in complicated effusions. Evidence for routine drainage is limited, but evacuation of the pleural space is indicated in complicated disease.

Educational aims

To demonstrate that pleural TB incorporates a wide spectrum of disease, ranging from self-resolving lymphocytic effusions to severe TB empyema with serious sequelae.To emphasise the high coexistence of pulmonary TB with pleural TB, and the importance of obtaining sputum for culture (induced if necessary) in all cases.To explore the significant diagnostic challenges posed by pleural TB, and consequently the frequent lack of information about drug sensitivity prior to initiating treatment.To highlight the influence of underlying TB prevalence in the population on the diagnostic accuracy of adjunctive investigations for the diagnosis of pleural TB.To discuss concerns around penetration of anti-TB medications into the pleural space and how this can influence decisions around treatment duration in practice.

Research progress of single-cell sequencing in tuberculosis

Tuberculosis is a major infectious disease caused by Mycobacterium tuberculosis infection. The pathogenesis and immune mechanism of tuberculosis are not clear, and it is urgent to find new drugs, diagnosis, and treatment targets. A useful tool in the quest to reveal the enigmas related to Mycobacterium tuberculosis infection and disease is the single-cell sequencing technique. By clarifying cell heterogeneity, identifying pathogenic cell groups, and finding key gene targets, the map at the single cell level enables people to better understand the cell diversity of complex organisms and the immune state of hosts during infection. Here, we briefly reviewed the development of single-cell sequencing, and emphasized the different applications and limitations of various technologies. Single-cell sequencing has been widely used in the study of the pathogenesis and immune response of tuberculosis. We review these works summarizing the most influential findings. Combined with the multi-molecular level and multi-dimensional analysis, we aim to deeply understand the blank and potential future development of the research on Mycobacterium tuberculosis infection using single-cell sequencing technology.

Single-cell profiling reveals distinct immune response landscapes in tuberculous pleural effusion and non-TPE

Background

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (Mtb) and remains a major health threat worldwide. However, a detailed understanding of the immune cells and inflammatory mediators in Mtb-infected tissues is still lacking. Tuberculous pleural effusion (TPE), which is characterized by an influx of immune cells to the pleural space, is thus a suitable platform for dissecting complex tissue responses to Mtb infection.

Methods

We employed singe-cell RNA sequencing to 10 pleural fluid (PF) samples from 6 patients with TPE and 4 non-TPEs including 2 samples from patients with TSPE (transudative pleural effusion) and 2 samples with MPE (malignant pleural effusion).

Result

Compared to TSPE and MPE, TPE displayed obvious difference in the abundance of major cell types (e.g., NK, CD4+T, Macrophages), which showed notable associations with disease type. Further analyses revealed that the CD4 lymphocyte population in TPE favored a Th1 and Th17 response. Tumor necrosis factors (TNF)-, and XIAP related factor 1 (XAF1)-pathways induced T cell apoptosis in patients with TPE. Immune exhaustion in NK cells was an important feature in TPE. Myeloid cells in TPE displayed stronger functional capacity for phagocytosis, antigen presentation and IFN-γ response, than TSPE and MPE. Systemic elevation of inflammatory response genes and pro-inflammatory cytokines were mainly driven by macrophages in patients with TPE.

Conclusion

We provide a tissue immune landscape of PF immune cells, and revealed a distinct local immune response in TPE and non-TPE (TSPE and MPE). These findings will improve our understanding of local TB immunopathogenesis and provide potential targets for TB therapy.

Exploring modulations in T-cell receptor-mediated T-cell signaling events in systemic circulation and at local disease site of patients with tubercular pleural effusion: An attempt to understand tuberculosis pathogenesis at the local disease site

Introduction

T cells are crucial for pathogenesis as well as control for tuberculosis (TB). Although much is known about the signaling pathways which are required for the activation of T cells during acute infection but the way these cells respond during persistent of infection still remained elusive. Therefore, it is rationale to understand T cell activation during tuberculous pleural effusion (TPE), which is similar to bacterial persistency system.

Methods

Herein, we will employ T cell receptor (TCR) based approaches for studying events of T cell activation pathways in cells of blood and pleural fluid among patients with TPE. We performed spectrofluorimetric analysis to study effect of M. tuberculosis antigens, ESAT-6 and Ag85A stimulation on intracellular calcium levels, Phosphorylation levels of ZAP-70 (Zeta-chain-associated protein kinase 70), PKC-θ (Protein kinase C theta), Erk1/2 (Extracellular signal-regulated kinase 1 and 2) and p-38 two important members of MAPKs (Mitogen activated Protein kinases) in CD3 and CD28 induced cells of blood and pleural fluid of same patients with TPE by western blotting. Patients with non-TPE were also included as matching disease controls in this study.

Results

We observed significantly higher intracellular calcium levels, Phosphorylation levels of ZAP-70, Erk1/2 and p-38 in CD3 and CD28 induced cells of pleural fluid as compared to the blood cells of same patients with TPE. Alteration in the activation of these events has also been noted after stimulation of ESAT-6 and Ag85A.

Discussion

Present study demonstrated up-regulated activation of TCR mediated T cell signaling events at local disease site (Pleural fluid) as compared to the blood sample of TB pleurisy patients which could be involved in T-cell dysfunctioning during the progression of the disease and also could be responsible for Th 1 dominance at local disease site in patients with TPE.

Single-cell immune profiling reveals functional diversity of T cells in tuberculous pleural effusion

Orchestration of an effective T lymphocyte response at infection sites is critical for protection against Mycobacterium tuberculosis (Mtb) infection. However, the local T cell immunity landscape in human tuberculosis is poorly defined. Tuberculous pleural effusion (TPE), caused by Mtb, is characterized by an influx of leukocytes to the pleural space, providing a platform suitable for delineating complex tissue responses to Mtb infection. Using single-cell transcriptomics and T cell receptor sequencing, we analyzed mononuclear cell populations in paired pleural fluid and peripheral blood of TPE patients. While all major cell clusters were present in both tissues, their relative proportions varied significantly by anatomic location. Lineage tracking analysis revealed subsets of CD8 and CD4 T cell populations with distinct effector functions specifically expanded at pleural sites. Granzyme K–expressing CD8 T cells were preferentially enriched and clonally expanded in pleural fluid from TPE, suggesting that they are involved in the pathogenesis of the disease. The findings collectively reveal the landscape of local T cell immunity in tuberculosis.

Pleural Tuberculosis

Pleural tuberculosis (TB) is common and often follows a benign course but may result in serious long-term morbidity. Diagnosis is challenging because of the paucibacillary nature of the condition. Advances in Mycobacterium culture media and PCR-based techniques have increased the yield from mycobacteriologic tests. Surrogate biomarkers perform well in diagnostic accuracy studies but must be interpreted in the context of the pretest probability in the individual patient. Confirming the diagnosis often requires biopsy, which may be acquired through thoracoscopy or image-guided closed pleural biopsy. Treatment is standard anti-TB therapy, with optional drainage and intrapleural fibrinolytics or surgery in complicated cases.

Anaphylatoxins orchestrate Th17 response via interactions between CD16+ monocytes and pleural mesothelial cells in tuberculous pleural effusion

The complement system is activated in tuberculous pleural effusion (TPE), with increased levels of the anaphylatoxins stimulating pleural mesothelial cells (PMCs) to secrete chemokines, which recruit nonclassical monocytes to the pleural cavity. The differentiation and recruitment of naive CD4⁺ T cells are induced by pleural cytokines and PMC-produced chemokines in TPE. However, it is unclear whether anaphylatoxins orchestrate CD4⁺ T cell response via interactions between PMCs and monocytes in TPE. In this study, CD16⁺ and CD16^- monocytes isolated from TPE patients were cocultured with PMCs pretreated with anaphylatoxins. After removing the PMCs, the conditioned monocytes were cocultured with CD4⁺ T cells. The levels of the cytokines were measured in PMCs and monocyte subsets treated separately with anaphylatoxins. The costimulatory molecules were assessed in conditioned monocyte subsets. Furthermore, CD4⁺ T cell response was evaluated in different coculture systems. The results indicated that anaphylatoxins induced PMCs and CD16⁺ monocytes to secrete abundant cytokines capable of only inducing Th17 expansion, but Th1 was feeble. In addition, costimulatory molecules were more highly expressed in CD16⁺ than in CD16⁻ monocytes isolated from TPE. The interactions between monocytes and PMCs enhanced the ability of PMCs and monocytes to produce cytokines and that of monocytes to express HLA-DR, CD40, CD80 and CD86, which synergistically induced Th17 expansion. In the above process, anaphylatoxins enhanced the interactions between monocytes and PMCs by increasing the level of the cytokines IL-1β, IL-6, IL-23 and upregulating the phenotype of CD40 and CD80 in CD16⁺ monocytes. Collectively, these data indicate that anaphylatoxins play a central role in orchestrating Th17 response mainly via interactions between CD16⁺ monocytes and PMCs in TPE.

Tuberculous pleural effusion is characterized by intense chronic accumulations of fluid and lymphocyte cells and monocytes/macrophages in the pleural space. Complement mediators play important roles in providing protection against Mycobacterium tuberculosis. Our results demonstrated that Mycobacterium tuberculosis infection induced the amplification of complement activation in TPE. Complement activation produces anaphylatoxins that induce PMCs and CD16⁺ monocytes to secrete abundant cytokines capable of only inducing Th17 expansion, but Th1 was feeble. In addition, costimulatory molecules were more highly expressed in CD16⁺ than in CD16⁻ monocytes isolated from TPE. The interactions between monocytes and PMCs enhanced the ability of PMCs and monocytes to produce cytokines and that of monocytes to express HLA-DR, CD40, CD80 and CD86, which synergistically induced Th17 expansion. In the above process, anaphylatoxins enhanced the interactions between monocytes and PMCs by increasing the level of the cytokines IL-1β, IL-6, IL-23 and upregulating the phenotype of CD40 and CD80 in CD16+ monocytes. In summary, these data highlighted the importance of anaphylatoxins and the innate immune system in eliciting pathogenic T cell responses in TPE and suggested that monocytes, especially the CD16⁺ subset, might be an efficient target for controlling inflammation.

Predominance of Th1 Immune Response in Pleural Effusion of Patients with Tuberculosis among Other Exudative Etiologies

Pleural tuberculosis (PlTB), a common form of extrapulmonary TB, remains a challenge in the diagnosis among many causes of pleural effusion. We recently reported that the combinatorial analysis of interferon gamma (IFN-γ), IFN-γ-inducible protein 10 (IP-10), and adenosine deaminase (ADA) from the pleural microenvironment was useful to distinguish pleural effusion caused by TB (microbiologically confirmed or not) among other etiologies. In this cross-sectional cohort study, a set of inflammatory mediators was quantified in blood and pleural fluid (PF) from exudative pleural effusion cases, including PlTB (n = 27) and non-PlTB (nTB) (n = 25) patients. The levels of interleukin-2 (IL-2), IL-4, IL-6, IL-10, IL-17A, IFN-γ, tumor necrosis factor (TNF), IP-10, transforming growth factor β1 (TGF-β), and ADA were determined using cytometric bead assay, enzyme-linked immunosorbent assay (ELISA), or biochemical tests. IFN-γ, IP-10, TNF, TGF-β, and ADA quantified in PF showed significantly higher concentrations in PlTB patients than in nTB patients. When blood and PF were compared, significantly higher concentrations of IL-6 and IL-10 in PF were identified in both groups. TGF-β, solely, showed significantly increased levels in PF and blood from PlTB patients when both clinical specimens were compared to those from nTB patients. Principal-component analysis (PCA) revealed a T helper type 1 (Th1) pattern attributed mainly to higher levels of IP-10, IFN-γ, TGF-β, and TNF in the pleural cavity, which was distinct between PlTB and nTB. In conclusion, our findings showed a predominantly cellular immune response in PF from TB cases, rather than other causes of exudative effusion commonly considered in the differential diagnosis of PlTB.

Evidence that changes in antimicrobial peptides during tuberculosis are related to disease severity, clinical presentation, specific therapy and levels of immune-endocrine mediators

Given the role of host defense peptides (HDPs) in the defensive response against mycobacteria, we analyzed the circulating levels of LL-37, β-defensin-2 and -3 in newly diagnosed patients with pulmonary (PTB) or pleural tuberculosis (PLTB) in whom measurements of pleural fluids were also performed. Severe PTB patients displayed higher circulating amounts of β-defensin-3, statistically different from controls, further decreasing upon antimycobacterial treatment. LL-37 concentrations appeared within the normal range at diagnosis, but tended to increase during treatment, becoming statistically upon its completion in moderate cases. PLTB patients revealed decreased levels of β-defensin-2 in presence of increased amounts of β-defensin-3 and LL-37; in their plasma or pleural fluids. Considering the immune-endocrine dysregulation of tuberculosis, we also performed correlation analysis detecting positive associations between levels of cortisol, IL-6 and β-defensin-3 in plasma from untreated severe patients as did their dehydroepiandrosterone and LL-37 values. Increased presence of β-defensins, may represent an attempt to improve defensive mechanisms; which also take part in the inflammatory reaction accompanying TB, reinforced by the association with immune-endocrine mediators. The divergent profile of PLTB patients, decreased β-defensin-2 but increased β-defensin-3 and LL-37 levels, suggests a differential role of these HDPs in a situation characterized for its better protective response.

Tuberculous pleural effusion

Tuberculous effusion is a common disease entity with a spectrum of presentations from a largely benign effusion, which resolves completely, to a complicated effusion with loculations, pleural thickening and even frank empyema, all of which may have a lasting effect on lung function. The pathogenesis is a combination of true pleural infection and an effusive hypersensitivity reaction, compartmentalized within the pleural space. Diagnostic thoracentesis with thorough pleural fluid analysis including biomarkers such as adenosine deaminase and gamma interferon achieves high accuracy in the correct clinical context. Definitive diagnosis may require invasive procedures to demonstrate histological evidence of caseating granulomas or microbiological evidence of the organism on smear or culture. Drug resistance is an emerging problem that requires vigilance and extra effort to acquire a complete drug sensitivity profile for each tuberculous effusion treated. Nucleic acid amplification tests such as Xpert MTB/RIF can be invaluable in this instance; however, the yield is low in pleural fluid. Treatment consists of standard anti-tuberculous therapy or a guideline-based individualized regimen in the case of drug resistance. There is low-quality evidence that suggests possible benefit from corticosteroids; however, they are not currently recommended due to concomitant increased risk of adverse effects. Small studies report some short- and long-term benefit from interventions such as therapeutic thoracentesis, intrapleural fibrinolytics and surgery but many questions remain to be answered.

Pleural tuberculosis: A concise clinical review

Tuberculosis (TB) is the leading infectious cause of death worldwide, and the commonest cause of death in people living with HIV. Globally, pleural TB remains one of the most frequent causes of pleural exudates, particularly in TB-endemic areas and in the HIV positive population. Most TB pleural effusions are exudates with high adenosine deaminase (ADA), lymphocyte-rich, straw-coloured and free flowing, with a low yield on mycobacterial culture. TB pleurisy can also present as loculated neutrophil-predominant effusions which mimic parapneumonic effusions. Rarely, they can present as frank TB empyema, containing an abundance of mycobacteria. Up to 80% of patients have parenchymal involvement on chest imaging. The diagnosis is simple if M. tuberculosis is detected in sputum, pleural fluid or biopsy specimens, and the recent advent of liquid medium culture techniques has increased the microbiological yield dramatically. Where the prevalence of TB is high the presence of a lymphocyte-predominant exudate with a high ADA has a positive predictive value of 98%. In low prevalence areas, the absence of an elevated ADA and lymphocyte predominance makes TB very unlikely, and pleural biopsy should be performed to confirm the diagnosis. Pleural biopsy for liquid culture and susceptibility testing must also be considered where the prevalence of drug resistant TB is high. Treatment regimens are identical to those administered for pulmonary TB. Initial pleural drainage may have a role in symptom relief and in hastening the resolution of the effusion. Surgical intervention may be required in loculated effusions and empyemas.

Programmed death-1+ T cells inhibit effector T cells at the pathological site of miliary tuberculosis

Optimal T cell activation is vital for the successful resolution of microbial infections. Programmed death-1 (PD-1) is a key immune check-point receptor expressed by activated T cells. Aberrant/excessive inhibition mediated by PD-1 may impair host immunity to Mycobacterium tuberculosis infection, leading to disseminated disease such as miliary tuberculosis (MTB). PD-1 mediated inhibition of T cells in pulmonary tuberculosis and TB pleurisy is reported. However, their role in MTB, particularly at the pathological site, remains to be addressed. The objective of this study was to investigate the role of PD-1-PD-ligand 1 (PD-L1) in T cell responses at the pathological site from patients of TB pleurisy and MTB as clinical models of contained and disseminated forms of tuberculosis, respectively. We examined the expression and function of PD-1 and its ligands (PD-L1-PD-L2) on host immune cells among tuberculosis patients. Bronchoalveolar lavage-derived CD3 T cells in MTB expressed PD-1 (54·2 ± 27·4%, P ≥ 0·0009) with significantly higher PD-1 ligand-positive T cells (PD-L1: 19·8 ± 11·8%; P ≥ 0·019, PD-L2: 12·6 ± 6·2%; P ≥ 0·023), CD19⁺ B cells (PD-L1: 14·4 ± 10·4%; P ≥ 0·042, PD-L2: 2·6 ± 1·43%; not significant) and CD14⁺ monocytes (PD-L1: 40·2 ± 20·1%; P ≥ 0·047, PD-L2: 22·4 ± 15·6%; P ≥ 0·032) compared with peripheral blood (PB) of MTB and healthy controls. The expression of PD-1 was associated with a diminished number of cells producing effector cytokines interferon (IFN)-γ, tumour necrosis factor (TNF)-α, interleukin (IL)-2 and elevated apoptosis. Locally accumulated T cells were predominantly PD-1⁺ -PD-L1⁺ , and blocking this pathway restores the protective T cell response. We conclude that M. tuberculosis exploits the PD-1 pathway to evade the host immune response by altering the T helper type 1 (Th1) and Th2 balance at the pathological site of MTB, thereby favouring disease dissemination.

Novel biomarker analysis of pleural effusion enhances differentiation of tuberculous from malignant pleural effusion

Lymphocytic pleurisy is commonly observed in tuberculosis and cancer. Noninvasive biomarkers are needed to distinguish tuberculous pleural effusion (TPE) from malignant pleural effusion (MPE) because current clinical diagnostic procedures are often invasive. We identified immune response biomarkers that can discriminate between TPE and MPE. Fourteen pleural effusion biomarkers were compared in 22 MPE patients and five TPE patients. Of the innate immunity biomarkers, the median levels of interleukin (IL)-1β and interferon-induced protein-10 (IP-10) were higher in TPE patients than in MPE patients (P<0.05 and P<0.01, respectively). Of the adaptive immunity biomarkers, the median levels of IL-13 and interferon-γ (IFN-γ) were higher in TPE patients than in MPE patients (P<0.05). In addition, the levels of basic fibroblast growth factor were higher in MPE patients than in TPE patients (P<0.05). Receiver operator characteristic analysis of these biomarkers was performed, resulting in the highest area under the curve (AUC) for IP-10 (AUC =0.95, 95% confidence interval, P<0.01), followed by IL-13 (AUC =0.86, 95% confidence interval, P<0.05). Our study shows that five biomarkers (IL-1β, IP-10, IFN-γ, IL-13, and basic fibroblast growth factor) have a potential diagnostic role in differentiating TPE from MPE, particularly in lung cancer-related MPE.

Characterization of CD4/CD8+ αβ and Vγ2Vδ2+ T cells in HIV-negative individuals with different Mycobacterium tuberculosis infection statuses

BACKGROUND

The immune responses of T cell subsets among patients with different Mycobacterium tuberculosis (M.tb) infection statuses [i.e., active tuberculosis (ATB), latent tuberculosis infection (LTBI) and non-infection (healthy control, HC)] have not been fully elucidated in HIV-negative individuals. Specifically, data are limiting in high tuberculosis epidemic regions in China. To investigate the distributions and functions of T cell subsets (i.e., CD3+, CD4+, CD8+ αβ and Vγ2Vδ2+ T cells) in HIV-negative subjects with different M.tb infection statuses, we conducted a case-control study that enrolled 125 participants, including ATB patients (n = 46), LTBI subjects (n = 34), and HC (n = 45).

RESULTS

An IFN-γ release assay (IGRA) was employed to screen LTBI subjects. Whole blood cell surface staining and flow cytometry were used to detect phenotypic distributions of T cells in the peripheral blood mononuclear cells (PBMCs) and tuberculous pleural fluid mononuclear cells (PFMCs). PPD and the phosphorylated antigen HMBPP were employed as stimulators for the detection of M.tb antigen-specific T cell functions via intracellular cytokine staining (ICS). The absolute numbers of T cell subsets, including CD3+ CD4+, CD3+ CD8+ αβ and Vγ2Vδ2+ T cells, were significantly reduced in active tuberculosis compared with latent tuberculosis or the healthy controls. Importantly, PPD-specific CD3+ CD4+ and CD3+ CD8+ αβ T cells and HMBPP-specific Vγ2Vδ2+ T cells in ATB patients were also significantly reduced compared to the LTBI/HC subjects (P<0.05). In contrast, the proportion of CD4+ T cells in PFMCs was higher compared to PBMCs, while CD8+ and Vγ2Vδ2+ T cells in PFMCs were lower compared to PBMCs (all P < 0.05). PPD-specific CD4+ T cells predominated among CD3+ T cells in PFMCs.

CONCLUSIONS

Cellular immune responses are impaired in ATB patients. Antigen-specific CD4+ T cell may migrate from the periphery to the lesion site, where they exert anti-tuberculosis functions.

Tuberculous pleural effusions: advances and controversies

On a global scale, tuberculosis (TB) remains one of the most frequent causes of pleural effusions. Our understanding of the pathogenesis of the disease has evolved and what was once thought to be an effusion as a result of a pure delayed hypersensitivity reaction is now believed to be the consequence of direct infection of the pleural space with a cascade of events including an immunological response. Pulmonary involvement is more common than previously believed and induced sputum, which is grossly underutilised, can be diagnostic in approximately 50%. The gold standard for the diagnosis of tuberculous pleuritis remains the detection of Mycobacterium tuberculosis in pleural fluid, or pleural biopsy specimens, either by microscopy and/or culture, or the histological demonstration of caseating granulomas in the pleura along with acid fast bacilli (AFB). In high burden settings, however, the diagnosis is frequently inferred in patients who present with a lymphocytic predominant exudate and a high adenosine deaminase (ADA) level, which is a valuable adjunct in the diagnostic evaluation. ADA is generally readily accessible, and together with lymphocyte predominance justifies treatment initiation in patients with a high pre-test probability. Still, false-negative and false-positive results remain an issue. When adding closed pleural biopsy to ADA and lymphocyte count, diagnostic accuracy approaches that of thoracoscopy. The role of other biomarkers is less well described. Early pleural drainage may have a role in selected cases, but more research is required to validate its use and to define the subpopulation that may benefit from such interventions.

PPE57 induces activation of macrophages and drives Th1-type immune responses through TLR2

Proline-glutamic acid (PE) and proline-proline-glutamic acid (PPE) are related proteins exclusive to Mycobacteria that play diverse roles in modulating critical innate immune pathways. In this study, we observed that the PPE57 protein is associated with the cell wall and is exposed on the cell surface. PPE57 enhances Mycobacterium spp. entering into macrophages and plays a role in macrophage phagocytosis. To explore the underlying mechanism, we demonstrated that PPE57 is able to recognise Toll-like receptor 2 (TLR2) and further induce macrophage activation by augmenting the expression of several cell surface molecules (CD40, CD80, CD86 and MHC class II) and pro-inflammatory cytokines (TNF-α, IL-6 and IL-12p40) within macrophages. These molecules are involved in the mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) signalling pathways. We demonstrated that PPE57 effectively polarises T cells to secrete interferon (IFN)-γ and IL-2 and to up-regulate CXCR3 expression in vivo and in vitro, suggesting that this protein may contribute to Th1 polarisation during the immune response. Moreover, recombinant Bacillus Calmette-Guérin (BCG) over-expressing PPE57 could provide better protective efficacy against Mycobacterium tuberculosis challenge compared with BCG. Taken together, our data provides several pieces of evidence that PPE57 may regulate innate and adaptive immunity by interacting with TLR2. These findings indicate that PPE57 protein is a potential antigen for the rational design of an efficient vaccine against M. tuberculosis.

KEY MESSAGES

PPE57 is located on the cell surface and enhances mycobacterium entry into macrophage. PPE57 interacts directly with TLR2 on macrophages. PPE57 plays a key role in the activation of macrophages in a TLR2-dependent manner. PPE57 induces a Th1 immune response via TLR2-mediated macrophage functions. Recombinant BCG over-expressing PPE57 could improve protective efficacy against M. tuberculosis.

CD4(+) CD25(high) forkhead box protein 3(+) regulatory T lymphocytes suppress interferon-γ and CD107 expression in CD4(+) and CD8(+) T cells from tuberculous pleural effusions

Tuberculous pleural effusion is characterized by a T helper type 1 (Th1) profile, but an excessive Th1 response may also cause tissue damage that might be controlled by regulatory mechanisms. In the current study we investigated the role of regulatory T cells (Treg ) in the modulation of Th1 responses in patients with tuberculous (TB) pleurisy. Using flow cytometry we evaluated the proportion of Treg (CD4(+) CD25(high) forkhead box protein 3(+) ), interferon (IFN)-γ and interleukin (IL)-10 expression and CD107 degranulation in peripheral blood (PB) and pleural fluid (PF) from patients with TB pleurisy. We demonstrated that the proportion of CD4(+) CD25(+) , CD4(+) CD25(high) FoxP3(+) and CD8(+) CD25(+) cells were increased in PF compared to PB samples. Mycobacterium tuberculosis stimulation increased the proportion of CD4(+) CD25(low/neg) IL-10(+) in PB and CD4(+) CD25(low/neg) IFN-γ(+) in PF; meanwhile, CD25(high) mainly expressed IL-10 in both compartments. A high proportion of CD4(+) CD107(+) and CD8(+) CD107(+) cells was observed in PF. Treg depletion enhanced the in-vitro M. tuberculosis-induced IFN-γ and CD4(+) and CD8(+) degranulation responses and decreased CD4(+) IL-10(+) cells in PF. Our results demonstrated that in TB pleurisy Treg cells effectively inhibit not only IFN-γ expression but also the ability of CD4(+) and CD8(+) cells to degranulate in response to M. tuberculosis.

Regulation of CD4(+) T cells by pleural mesothelial cells via adhesion molecule-dependent mechanisms in tuberculous pleurisy

Background

Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) have been demonstrated to be expressed on pleural mesothelial cells (PMCs), and to mediate leukocyte adhesion and migration; however, little is known about whether adhesion molecule-dependent mechanisms are involved in the regulation of CD4⁺ T cells by PMCs in tuberculous pleural effusion (TPE).

Methods

Expressions of ICAM-1 and VCAM-1 on PMCs, as well as expressions of CD11a and CD29, the counter-receptors for ICAM-1 and VCAM-1, respectively, expressed on CD4⁺ T cells in TPE were determined using flow cytometry. The immune regulations on adhesion, proliferation, activation, selective expansion of CD4⁺ helper T cell subgroups exerted by PMCs via adhesion molecule-dependent mechanisms were explored.

Results

Percentages of ICAM-1-positive and VCAM-1‒positive PMCs in TPE were increased compared with PMC line. Interferon-γ enhanced fluorescence intensity of ICAM-1, while IL-4 promoted VCAM-1 expression on PMCs. Percentages of CD11a^highCD4⁺ and CD29^highCD4⁺ T cells in TPE significantly increased as compared with peripheral blood. Prestimulation of PMCs with anti‒ICAM-1 or ‒VCAM-1 mAb significantly inhibited adhesion, activation, as well as effector regulatory T cell expansion induced by PMCs.

Conclusions

Our current data showed that adhesion molecule pathways on PMCs regulated adhesion and activation of CD4⁺ T cells, and selectively promoted the expansion of effector regulatory T cells.

Levels of inflammatory cytokines, adrenal steroids, and mRNA for GRα, GRβ and 11βHSD1 in TB pleurisy

Our previous work on the immune-endocrine features of patients with pulmonary tuberculosis (TB) showed markedly decreased plasma levels of dehydroepiandrosterone (DHEA) together with augmented concentrations of Cortisol and pro- and anti-inflammatory cytokines. Studies in peripheral blood mononuclear cells (PBMC) indicated a lower mRNA α/β ratio of glucocorticoid receptors -GR- together with a higher 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) mRNA expression in cases with severe pulmonary TB. Since Pleural TB (PLTB) is a rather benign manifestation of TB, we now analyzed the systemic and local immune-endocrine profile as well as the GRα, GRβ, 11βHSD1 and 11βHSD2 transcripts in PBMC and pleural effusion mononuclear cells (PEMC) of patients with PLTB. PLTB patients had increased levels of IL-1β, IL-6 and IFNγ together with reduced Cortisol and DHEA concentrations in pleural fluids. Also, a significantly increased expression of 11βHSD1 and GRα was found in PEMC compared to PBMC. Findings point out to an appropriate immune response and a substantial inflammatory reaction, wherein the low Cortisol concentrations may be equally effective, because of the increased expression of GRα and 11βHSD1 transcripts which may optimize the immunomodulatory properties of Cortisol.

Immunohistological characterization of spinal TB granulomas from HIV-negative and -positive patients

Tuberculosis (TB) is mainly a disease of the lungs, but Mycobacterium tuberculosis (Mtb) can establish infection in virtually any organ in the body. Rising rates of extrapulmonary (EP) TB have been largely associated with the HIV epidemic, as patients co-infected with HIV show a four-fold higher risk of EPTB. Spinal TB (Pott's Disease), one of the most debilitating extrapulmonary forms of disease, is difficult to diagnose and can cause deformity and/or neurological deficits. This study examined the histopathology and distribution of immune cells within spinal TB lesions and the impact of HIV on pathogenesis. The overall structure of the spinal granulomas resembled that seen in lung lesions from patients with pulmonary TB. Evidence of efficient macrophage activation and differentiation were detectable within organized structures in the spinal tissue, irrespective of HIV status. Interestingly, the granulomatous architecture and macroscopic features were similar in all samples examined, despite a reversal in the ratio of infiltrating CD4 to CD8 T cells in the lesions from HIV-infected patients. This study provides a foundation to understand the mechanism of tissue destruction and disease progression in Spinal TB, enabling the future development of novel therapeutic strategies and diagnostic approaches for this devastating disease.

Frequency of regulatory T-cells in the peripheral blood of patients with pulmonary tuberculosis from shanxi province, china

BACKGROUND

Tuberculosis (TB) is a disease caused by the chronic and continuous infection of the pathogen Mycobacterium tuberculosis (M. tuberculosis). M. tuberculosis is an intracellular bacterial pathogen and is eliminated mainly through CD4(+) effector Th cells. M. tuberculosis induces regulatory T lymphocytes (Tregs) that mediate immune suppression by cell-to-cell contact or by secreting cytokines such as transforming growth factor-β (TGF-β). To understand the role of regulatory T-cells in the pathogenesis of TB, we have measured the in vivo frequency of regulatory T-cells and associated in vivo cytokine production in pulmonary tuberculosis patients.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we analyzed blood samples from 3 different populations (Group 1: patients with active TB, Group 2: patients recovered from TB and Group 3: healthy controls). We measured natural regulatory T-cell expression in peripheral blood using flow cytometry, and levels of blood serum IFN-γ and TGF-β1 using ELISA. The in vivo function of inductive regulatory T cells was mainly indicated by the expression of IFN-γ, TGF-β1, etc. Frequencyof natural regulatory T cells and inductive regulatory T cells in the peripheral blood samples from Group 1 patients were all significantly higher (P<0.05) than those from Groups 2 and 3.

CONCLUSION/SIGNIFICANCE

Our results indicate that frequency of natural regulatory T cells and inductive regulatory T cells are significantly higher in the peripheral blood of patients with active pulmonary tuberculosis. These findings have potential application in improving TB diagnostic methods.

Recruitment of Th1 effector cells in human tuberculosis: hierarchy of chemokine receptor(s) and their ligands

Selective recruitment of IFN-γ biased Th1 effector cells at the pathologic site(s) determines the local immunity of tuberculosis (TB). We observed the enrichment of CXCR3, CCR5 and CD11a(high) T cells in the peripheral blood, pleural fluid and bronchoalveolar lavage of TB pleural effusion (TB-PE) and miliary tuberculosis (MTB) patients respectively. CXCR3(+)CCR5(+) T cells were significantly high at the local disease site(s) in both the forms of TB and their frequency was highest among activated lymphocytes in TB-PE. Interestingly, all CCR5(+) cells were invariably positive for CXCR3 but all CXCR3(+) cells did not co-express CCR5 in pleural fluid whereas the situation was reverse in bronchoalveolar lavage. These CXCR3(+)CCR5(+) cells dominantly produced IFN-γ in response to Mycobacterium tuberculosis antigen. In vitro chemotaxis assay indicates dominant role of RANTES and IP-10 in the selective recruitment of CXCR3(+)CCR5(+)cells at the tubercular pathologic sites.

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.

Induction of CCL8/MCP-2 by mycobacteria through the activation of TLR2/PI3K/Akt signaling pathway

Pleural tuberculosis (TB), together with lymphatic TB, constitutes more than half of all extrapulmonary cases. Pleural effusions (PEs) in TB are representative of lymphocytic PEs which are dominated by T cells. However, the mechanism underlying T lymphocytes homing and accumulation in PEs is still incompletely understood. Here we performed a comparative analysis of cytokine abundance in PEs from TB patients and non-TB patients by protein array analysis and observed that MCP-2/CCL8 is highly expressed in the TB-PEs as compared to peripheral blood. Meanwhile, we observed that CCR5, the primary receptor used by MCP-2/CCL8, is mostly expressed on pleural CD4⁺ T lymphocytes. Furthermore, we found that infection with either Mycobacterium bovis Bacillus Calmette-Guérin (BCG) or Mycobacterium tuberculosis H37Rv induced production of MCP-2/CCL8 at both transcriptional and protein level in Raw264.7 and THP-1 macrophage cells, mouse peritoneal macrophages as well as human PBMC monocyte-derived macrophages (MDMs). The induction of MCP-2/CCL8 by mycobacteria is dependent on the activation of TLR2/PI3K/Akt and p38 signaling pathway. We conclude that accumulation of MCP-2/CCL8 in TB-PEs may function as a biomarker for TB diagnosis.

Significance of the frequency of CD4+CD25+CD127- T-cells in patients with pulmonary tuberculosis and diabetes mellitus

BACKGROUND AND OBJECTIVE

Pulmonary tuberculosis and diabetes mellitus (DM) are closely associated. The objective of this study was to determine whether the expression of CD4+CD25+CD127- T-cells (regulatory T-cells (Treg)) is associated with diabetic pulmonary tuberculosis.

METHODS

Flow cytometry was used to determine the frequencies of CD4+CD25+ and CD4+CD25+CD127- T-cells in peripheral blood, bronchoalveolar lavage fluid (BALF) and pleural effusions from 120 patients (30 with pulmonary tuberculosis and DM (TBDM), 30 with pulmonary tuberculosis without DM (TB), 30 with tuberculous pleurisy without DM (TBP) and 30 healthy volunteers). The concentrations of interferon (IFN)-γ and interleukin (IL)-10 in BALF and pleural effusions were determined by enzyme-linked immunosorbent assay.

RESULTS

Treg frequencies in peripheral blood were significantly higher in patients with TBDM, TB and TBP than in the control group, with the frequency in TBDM being the highest (P < 0.01 for all). In TBP patients, Treg frequencies were significantly lower in pleural effusions than in peripheral blood. In TB patients, Treg frequencies in BALF and peripheral blood were not significantly different. However, in TBDM patients, Treg frequencies were significantly higher in BALF than in peripheral blood. IL-10 expression was significantly higher, and IFN-γ expression was significantly lower in BALF of TBDM patients compared with BALF and pleural effusions of TB patients.

CONCLUSIONS

In patients with pulmonary tuberculosis and DM, the imbalance between Treg and effector T-cells at pathological sites may be associated with weakened immunity and clinical manifestations of TB.

Foxp3+ regulatory T cells among tuberculosis patients: impact on prognosis and restoration of antigen specific IFN-γ producing T cells

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) and programmed death-1 (PD-1) molecules have emerged as pivotal players in immune suppression of chronic diseases. However, their impact on the disease severity, therapeutic response and restoration of immune response in human tuberculosis remains unclear. Here, we describe the possible role of Treg cells, their M. tuberculosis driven expansion and contribution of PD-1 pathway to the suppressive function of Treg cells among pulmonary tuberculosis (PTB) patients. Multicolor flow cytometry, cell culture, cells sorting and ELISA were employed to execute the study. Our results showed significant increase in frequency of antigen-reactive Treg cells, which gradually declined during successful therapy and paralleled with decline of M. tuberculosis-specific IL-10 along with elevation of IFN-γ production, and raising the IFN-γ/IL-4 ratio. Interestingly, persistence of Treg cells tightly correlated with MDR tuberculosis. Also, we show that blocking PD-1/PD-L1 pathway abrogates Treg-mediated suppression, suggesting that the PD-1/PD-L1 pathway is required for Treg-mediated suppression of the antigen-specific T cells. Treg cells possibly play a role in dampening the effector immune response and abrogating PD-1 pathway on Treg cells significantly rescued protective T cell response, suggesting its importance in immune restoration among tuberculosis patients.

Impaired expression of CD26 compromises T-cell recruitment in human visceral leishmaniasis

An inefficient Th1 response, coupled with skewed Th2 cytokine production, has been implicated to increase susceptibility to visceral leishmaniasis (VL) infection. The expression of the dipeptidyl peptidase Cd26 by polarized Th1 activates a chemokine cascade that recruits Th1 recruitment to the pathologic site. Here, we studied 42 patients with confirmed VL (mean age 24.80 ± 16.26 years; range 3-70 years; 25 males and 17 females), 30 endemic controls, and 10 nonendemic controls. We observed a decrease in constitutive and antigen-induced expression of CD26 on the T cells of VL patients. Soluble CD26 (sCD26) levels in serum and BM were also found to be significantly lower in VL patients. Following successful therapy, increased sCD26 expression was observed. Tuberculosis pleural effusion derived CCR5(+) CXCR3(+) effector T cells showed enhanced chemokine-driven migration in the presence of posttreatment BM aspirate containing high levels of sCD26. Moreover, T-cell migration could be inhibited by blocking RANTES, IP-10, and CD26 signaling from the posttreatment aspirate with Ab. Our results indicate that, in VL patients, impaired expression and secretion of CD26 compromises chemokine activation and thus T-cell recruitment, eventually resulting in a deficient state of local immunity at pathologic sites.

Immune responses in the lungs of patients with tuberculous pleural effusion without pulmonary tuberculosis

Background

Tuberculous pleural effusion (TPE) is one of the most common forms of extrapulmonary tuberculosis. Because most studies of TPE focused on the pleural space, little information regarding lung parenchyma is available. We therefore aimed to investigate immune responses in the lung parenchyma of TPE patients without pulmonary tuberculosis.

Methods

Patients with any evidence of pulmonary tuberculosis, either from radiologic or bacteriologic evaluation, were excluded. Bronchoalveolar lavage fluid (BALF) was collected from 10 newly diagnosed, untreated, HIV-negative TPE patients and 10 healthy controls. We analyzed T-lymphocyte subpopulations and measured 10 cytokines in BALF. Cytokine levels in BALF were standardised using urea.

Results

The concentrations of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), vascular endothelial growth factor (VEGF), and the CD4+/CD8+ ratio of T-lymphocytes were significantly higher in TPE patients without pulmonary tuberculosis than in the controls. Of the cytokines measured in BALF, VEGF showed the highest concentration. No difference was observed in T-helper type 2 cytokines between the 2 groups.

Conclusion

There were significant immune responses and increases in IFN-γ, TNF-α, and VEGF in the lung parenchyma of TPE patients without pulmonary tuberculosis. This result suggests that TPE may induce a significant immune response in lung parenchyma.

Differentiation and recruitment of IL-22-producing helper T cells stimulated by pleural mesothelial cells in tuberculous pleurisy

RATIONALE

IL-22-producing helper T cells (Th22 cells) have been reported to be involved in tuberculosis infection. However, differentiation and immune regulation of Th22 cells in tuberculous pleural effusion (TPE) remain unknown.

OBJECTIVES

To elucidate the mechanism by which Th22 cells differentiate and recruit into the pleural space.

METHODS

The distribution and phenotypic features of Th22 cells in both TPE and blood were determined. The impacts of proinflammatory cytokines and antigen presentation by pleural mesothelial cells (PMCs) on Th22-cell differentiation were explored. The chemoattractant activity of chemokines produced by PMCs for Th22 cells was observed.

MEASUREMENTS AND MAIN RESULTS

Th22 cells were significantly higher in TPE than in blood. IL-1β, IL-6, and/or tumor necrosis factor-α promoted Th22-cell differentiation from CD4(+) T cells. It was found that PMCs expressed CCL20, CCL22, and CCL27, and that TPE and PMC supernatants were chemotactic for Th22 cells. This activity was partly blocked by anti-CCL20, anti-CCL22, and anti-CCL27 antibodies. IL-22 and IL-17 significantly improved PMC wound healing. Moreover, PMCs were able to stimulate CD4(+) T-cell proliferation and Th22-cell differentiation by presenting tuberculosis-specific antigen.

CONCLUSIONS

The overrepresentation of Th22 cells in TPE may be due to pleural cytokines and to PMC-produced chemokines. Our data suggest a collaborative loop between PMCs and Th22 cells in TPE. In particular, PMCs were able to function as antigen-presenting cells to stimulate CD4(+) T-cell proliferation and Th22-cell differentiation.

Differentiation and recruitment of Th9 cells stimulated by pleural mesothelial cells in human Mycobacterium tuberculosis infection

Newly discovered IL-9–producing CD4⁺ helper T cells (Th9 cells) have been reported to contribute to tissue inflammation and immune responses, however, differentiation and immune regulation of Th9 cells in tuberculosis remain unknown. In the present study, our data showed that increased Th9 cells with the phenotype of effector memory cells were found to be in tuberculous pleural effusion as compared with blood. TGF-β was essential for Th9 cell differentiation from naïve CD4⁺ T cells stimulated with PMA and ionomycin in vitro for 5 h, and addition of IL-1β, IL-4 or IL-6 further augmented Th9 cell differentiation. Tuberculous pleural effusion and supernatants of cultured pleural mesothelial cells were chemotactic for Th9 cells, and this activity was partly blocked by anti-CCL20 antibody. IL-9 promoted the pleural mesothelial cell repairing and inhibited IFN-γ-induced pleural mesothelial cell apoptosis. Moreover, pleural mesothelial cells promoted Th9 cell differentiation by presenting antigen. Collectively, these data provide new information concerning Th9 cells, in particular the collaborative immune regulation between Th9 cells and pleural mesothelial cells in human M. tuberculosis infection. In particular, pleural mesothelial cells were able to function as antigen-presenting cells to stimulate Th9 cell differentiation.

Immune response to Mycobacterium tuberculosis infection in the parietal pleura of patients with tuberculous pleurisy

The T lymphocyte-mediated immune response to Mycobacterium tuberculosis infection in the parietal pleura of patients with tuberculous pleurisy is unknown. The aim of this study was to investigate the immune response in the parietal pleura of tuberculous pleurisy compared with nonspecific pleuritis. We have measured the numbers of inflammatory cells particularly T-cell subsets (Th1/Th2/Th17/Treg cells) in biopsies of parietal pleura obtained from 14 subjects with proven tuberculous pleurisy compared with a control group of 12 subjects with nonspecific pleuritis. The number of CD3+, CD4+ and CCR4+ cells and the expression of RORC2 mRNA were significantly increased in the tuberculous pleurisy patients compared with the nonspecific pleuritis subjects. The number of toluidine blue+ cells, tryptase+ cells and GATA-3+ cells was significantly decreased in the parietal pleura of patients with tuberculous pleurisy compared with the control group of nonspecific pleuritis subjects. Logistic regression with receiver operator characteristic (ROC) analysis for the three single markers was performed and showed a better performance for GATA-3 with a sensitivity of 75%, a specificity of 100% and an AUC of 0.88. There was no significant difference between the two groups of subjects in the number of CD8, CD68, neutrophil elastase, interferon (IFN)-γ, STAT4, T-bet, CCR5, CXCR3, CRTH2, STAT6 and FOXP3 positive cells. Elevated CD3, CD4, CCR4 and Th17 cells and decreased mast cells and GATA-3+ cells in the parietal pleura distinguish patients with untreated tuberculous pleurisy from those with nonspecific pleuritis.

Diagnostic accuracy of T-cell interferon-γ release assays in tuberculous pleurisy: a meta-analysis

BACKGROUND AND OBJECTIVE

The diagnosis of tuberculous pleurisy by analysis of pleural fluid using standard diagnostic tools is difficult. Recently, T-cell interferon-γ release assays (IGRA) have been introduced for the diagnosis of tuberculous pleurisy. The aim of the present meta-analysis was to establish the overall diagnostic accuracy of IGRA on both pleural fluid and peripheral blood, for diagnosing tuberculous pleurisy.

METHODS

A systematic review was performed of English language publications. Sensitivity, specificity and other measures of the accuracy of IGRA for the diagnosis tuberculous pleurisy using both pleural fluid and blood were pooled using a random-effects model or a fixed-effects model. Receiver operating characteristic curves were used to summarize overall test performance.

RESULTS

Seven out of eight studies met the inclusion criteria. The summary estimates of sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value, negative predictive value and diagnostic odds ratio were, for pleural fluid: 0.75, 0.82, 3.49, 0.24, 0.85, 0.70 and 19.04, respectively; and for blood: 0.80, 0.72, 2.86, 0.28, 0.78, 0.74 and 11.06, respectively.

CONCLUSIONS

As almost 20% of non-tuberculosis patients would be erroneously treated for tuberculosis and 25% of patients with tuberculous pleurisy would be missed, pleural fluid IGRA are not useful for the clinical diagnosis of tuberculous pleurisy.

Polyfunctional Mycobacterium tuberculosis-specific effector memory CD4+ T cells at sites of pleural TB

Pleural tuberculosis (TB) is a common presentation of Mycobacterium tuberculosis (MTB) infection, and despite spontaneous resolution remains a strong risk factor for reactivation pulmonary TB in a majority of individuals. This study was undertaken to further understand the characteristics of immune cells at sites of pleural TB. A significant shift toward memory CD4+ T cells with an effector phenotype and away from naïve CD4+ T cells in pleural fluid as compared to blood mononuclear cells was found. These data suggest that effector T cells are capable of migrating to sites of active TB infection and/or the differentiation to effector phenotype T cells in situ is highly amplified. Using multi-parameter flow cytometry analysis, a significant portion of MTB-specific CD4+ T cells in the pleural space were polyfunctional demonstrating two, three or four simultaneous functions including IFN-gamma, IL-2, TNF-alpha, and or MIP-1 alpha production. A greater proportion of these polyfunctional cells were of effector memory rather than central memory phenotype. The role of these polyfunctional MTB-specific CD4+ T cells at sites of pleural TB requires further study.

Protective cellular responses to Burkholderia mallei infection

Burkholderia mallei is a Gram-negative bacillus causing the disease glanders in humans. During intraperitoneal infection, BALB/c mice develop a chronic disease characterised by abscess formation where mice normally die up to 70 days post-infection. Although cytokine responses have been investigated, cellular immune responses to B. mallei infection have not previously been characterised. Therefore, the influx and activation status of splenic neutrophils, macrophages and T cells was examined during infection. Gr-1+ neutrophils and F4/80+ macrophages infiltrated the spleen 5 h post-infection and an increase in activated macrophages, neutrophils and T cells occurred by 24 h post-infection. Mice depleted of Gr-1+ cells were acutely susceptible to B. mallei infection, succumbing to the infection 5 days post-infection. Mice depleted of both CD4 and CD8 T cells did not succumb to the infection until 14 days post-infection. Infected μMT (B cell) and CD28 knockout mice did not differ from wildtype mice whereas iNOS-2 knockout mice began to succumb to the infection 30 days post-infection. The data presented suggests that Gr-1+ cells, activated early in B. mallei infection, are essential for controlling the early, innate response to B. mallei infection and T cells or nitric oxide are important during the later stages of infection.

CCL5 participates in early protection against Mycobacterium tuberculosis

Control of M.tb, the causative agent of TB, requires immune cell recruitment to form lung granulomas. The chemokines and chemokine receptors that promote cell migration for granuloma formation, however, are not defined completely. As immunity to M.tb manifests slowly in the lungs, a better understanding of specific roles for chemokines, in particular those that promote M.tb-protective T(H)1 responses, may identify targets that could accelerate granuloma formation. The chemokine CCL5 has been detected in patients with TB and implicated in control of M.tb infection. To define a role for CCL5 in vivo during M.tb infection, CCL5 KO mice were infected with a low dose of aerosolized M.tb. During early M.tb infection, CCL5 KO mice localized fewer APCs and chemokine receptor-positive T cells to the lungs and had microscopic evidence of altered cell trafficking to M.tb granulomas. Early acquired immunity and granuloma function were transiently impaired when CCL5 was absent, evident by delayed IFN-gamma responses and poor control of M.tb growth. Lung cells from M.tb-infected CCL5 KO mice eventually reached or exceeded the levels of WT mice, likely as a result of partial compensation by the CCL5-related ligand, CCL4, and not because of CCL3. Finally, our results suggest that most T cells use CCR5 but not CCR1 to interact with these ligands. Overall, these results contribute to a model of M.tb granuloma formation dependent on temporal regulation of chemokines rather than on redundant or promiscuous interactions.

CCL22 is involved in the recruitment of CD4+CD25 high T cells into tuberculous pleural effusions

BACKGROUND AND OBJECTIVE

CD4(+)CD25(high) regulatory T cells are increased in tuberculous pleural effusions (TPE). However, the mechanism by which CD4(+)CD25(high) T cells infiltrate into the pleural cavity is unknown. The aim of this study was to investigate whether the chemokines CCL22 and CCL17 are present in TPE, and the chemoattractant activity of these chemokines for infiltration of CD4(+)CD25(high) T cells into the pleural space.

METHODS

The concentrations of CCL22 and CCL17 were measured in pleural effusions from 33 patients with tuberculous pleurisy, 21 patients with pleural bacterial infections and 18 patients with transudative pleural effusions. T lymphocyte subsets in pleural effusions were assessed by flow cytometry. Pleural effusion cells were analysed for the expression of CCL22. The chemoattractant activity of CCL22 for CD4(+)CD25(high) T cells was assessed in vitro.

RESULTS

The frequency of CD4(+)CD25(high) T cells was significantly higher in TPE than in blood. High concentrations of CCL22 were detected in tuberculous effusions, but not in bacterial effusions or transudates. Macrophages and T cells in TPE expressed CCL22. Tuberculous pleural fluid was chemotactic for CD4(+)CD25(high) T cells in vitro, and anti-CCL22 antibody partly inhibited this chemotactic activity.

CONCLUSIONS

CCL22 appeared to be increased in TPE compared with bacterial pleural effusions or transudates. CCL22 may be responsible for the infiltration of CD4(+)CD25(high) T cells into the pleural space of patients with tuberculous pleurisy.

NK cells from tuberculous pleurisy express high ICAM-1 levels and exert stimulatory effect on local T cells

Tuberculous pleurisy, one of the most common manifestations of extrapulmonary tuberculosis, is characterized by a T-cell-mediated hypersensitivity reaction along with a Th1 immune profile. In this study, we investigated functional cross-talk among T and NK cells in human tuberculous pleurisy. We found that endogenously activated pleural fluid-derived NK cells express high ICAM-1 levels and induce T-cell activation ex vivo through ICAM-1. Besides, upon in vitro stimulation with monokines and PAMP, resting peripheral blood NK cells increased ICAM-1 expression leading to cellular activation and Th1 polarization of autologous T cells. Furthermore, these effects were abolished by anti-ICAM-1 Ab. Hence, NK cells may contribute to the adaptive immune response by a direct cell-contact-dependent mechanism in the context of Mycobacterium tuberculosis infection.

CD3 expression distinguishes two gammadeltaT cell receptor subsets with different phenotype and effector function in tuberculous pleurisy

Tuberculous pleurisy is a naturally occurring site of Mycobacterium tuberculosis (Mtb) infection. Herein, we describe the expression of activation, natural killer (NK) and cell migration markers, as well as effector functions from gammadeltaT cells in peripheral blood (PB) and pleural effusion (PE) from tuberculosis patients (TB). We observed a decreased percentage of circulating gammadeltaT from TB patients and differential expression of NK as well as of chemokine receptors on PB and PE. Two subsets of gammadeltaT cells were differentiated by the CD3/gammadeltaT cell receptor (gammadeltaTCR) complex. The gammadeltaTCR(low) subset had a higher CD3 to TCR ratio and was enriched in Vdelta2(+) cells, whereas most Vdelta1(+) cells belonged to the gammadeltaTCR(high) subset. In PB from TB, most gammadeltaTCR(high) were CD45RA(+)CCR7(-) and gammadeltaTCR(low) were CD45RA(+/-)CCR7(+)CXCR3(+). In the pleural space the proportion of CD45RA(-)CCR7(+)CXCR3(+) cells was higher. Neither spontaneous nor Mtb-induced interferon (IFN)-gamma production was observed in PB-gammadeltaT cells from TB; however, PE-gammadeltaT cells showed a strong response. Both PB- and PE-gammadelta T cells expressed surface CD107a upon stimulation with Mtb. Notably, PE-gammadeltaTCR(low) cells were the most potent effector cells. Thus, gammadeltaT cells from PB would acquire a further activated phenotype within the site of Mtb infection and exert full effector functions. As gammadeltaT cells produce IFN-gamma within the pleural space, they would be expected to play a beneficial role in tuberculous pleurisy by helping to maintain a T helper type 1 profile.

Effects of prednisolone on the systemic release of mediators of cell-mediated cytotoxicity during human endotoxemia

Corticosteroids are widely used for the suppression of cell-mediated cytoxicity. This process is mediated by natural killer cells and cytotoxic T lymphocytes, and their activation can be monitored by levels of the chemokines CXCL9 and CXCL10, the degranulation product granzymes A and B, and by levels of secretory phospholipase A2. The current study aimed to determine the effects of increasing doses of prednisolone on the release of these mediators in healthy humans exposed to LPS. Therefore, 32 healthy men received prednisolone orally at doses of 0, 3, 10, or 30 mg (n = 8 per group) at 2 h before intravenous injection of Escherichia coil LPS (4 ng/kg). Prednisolone dose-dependently attenuated the LPS-induced rises in the plasma concentrations of the chemokines CXCL9 and CXCL10, as well as of granzymes A and B levels. CXCL10 and granzyme B release were most sensitive to prednisolone, with a significant inhibition already achieved at the lowest prednisolone dose (3 mg). The levels of secretory phospholipase A2 were increased after LPS administration but were not significantly affected by prednisolone. This study demonstrates that prednisolone differentially inhibits the systemic release of mediators involved in cell-mediated cytotoxicity in humans in vivo.

Mycobacterial lipopeptides elicit CD4+ CTLs in Mycobacterium tuberculosis-infected humans

In searching for immunogenic molecules with the potential to induce protective immune responses against tuberculosis, we developed an ex vivo model to study frequency, phenotype, and effector functions of human T lymphocytes recognizing hydrophobic Ags of Mycobacterium tuberculosis (M.Tb). To obtain unbiased results, we characterized T lymphocytes responding to a crude cell wall extract (chloroform methanol extract of M.Tb (M.Tb-CME)) containing a broad spectrum of mycobacterial glycolipids and lipopeptides. A significant proportion of T lymphocytes recognized M.Tb-CME (290 IFN-gamma+ T cells/10(5) PBMCs) and developed to effector memory cells as determined by the expression of CD45RO and the chemokine receptors CXCR3 and CCR5. Expanded lymphocytes fulfilled all criteria required for an efficient immune response against tuberculosis: 1) release of macrophage-activating Th1 cytokines and chemokines required for the spatial organization of local immune responses, 2) cytolytic activity against Ag-pulsed macrophages, and 3) recognition of infected macrophages and killing of the intracellular bacteria. Phenotypically, M.Tb-CME-expanded cells were CD4+ and MHC class II restricted, challenging current concepts that cytotoxic and antimicrobial effector cells are restricted to the CD8+ T cell subset. Pretreatment of M.Tb-CME with protease or chemical delipidation abrogated the biological activity, suggesting that responses were directed toward mycobacterial lipopeptides. These findings suggest that lipidated peptides are presented by M.Tb-infected macrophages and elicit CD4+ cytolytic and antimicrobial T lymphocytes. Our data support an emerging concept to include hydrophobic microbial Ags in vaccines against tuberculosis.

Sphingosine 1-phosphate promotes antigen processing and presentation to CD4+ T cells in Mycobacterium tuberculosis-infected monocytes

Sphingosine 1-phosphate (S1P) has recently been described to induce antimycobacterial activity. The present study analyses the role played by S1P in antigen presentation of monocytes and in the next activation of Mycobacterium tuberculosis (MTB)-specific CD4+ T cell response. Results reported herein show that S1P stimulation of MTB-infected monocytes (i) inhibits intracellular mycobacterial growth, (ii) enhances phagolysosome maturation and the transit of mycobacteria in MHC class II compartments, (iii) increases the frequency of MTB-specific CD4+CD69+ T cells, expressing the inflammatory homing receptor CCR5, derived from tuberculosis patients and PPD+, BCG naïve, healthy subjects, and (iv) induces IFN-gamma production in CD4+CD69+CCR5+ T cells derived from PPD+ healthy individuals, only. Altogether, these results show that S1P promotes antigen processing and presentation in monocytes, increases the frequency of MTB-specific CD4+ T cells and can regulate IFN-gamma production by antigen specific CD4+ T cells in the course of active disease.

Diagnosis and treatment of tuberculous pleural effusion in 2006

Tuberculous (TB) pleural effusion occurs in approximately 5% of patients with Mycobacterium tuberculosis infection. The HIV pandemic has been associated with a doubling of the incidence of extrapulmonary TB, which has resulted in increased recognition of TB pleural effusions even in developed nations. Recent studies have provided insights into the immunopathogenesis of pleural TB, including memory T-cell homing and chemokine activation. The definitive diagnosis of TB pleural effusions depends on the demonstration of acid-fast bacilli in the sputum, pleural fluid, or pleural biopsy specimens. The diagnosis can be established in a majority of patients from the clinical features, pleural fluid examination, including cytology, biochemistry, and bacteriology, and pleural biopsy. Measurement of adenosine deaminase and interferon-gamma in the pleural fluid and polymerase chain reaction for M tuberculosis has gained wide acceptance in the diagnosis of TB pleural effusions. Although promising, these tests require further evaluation before their routine use can be recommended. The treatment of TB pleural effusions in patients with HIV/AIDS is essentially similar to that in HIV-negative patients. At present, evidence regarding the use of corticosteroids in the treatment of TB pleural effusion is not clear-cut.

Life and death in the granuloma: immunopathology of tuberculosis

During tuberculosis (TB) infection, the granuloma provides the microenvironment in which antigen-specific T cells colocate with and activate infected macrophages to inhibit the growth of Mycobacterium tuberculosis. Although the granuloma is the site for mycobacterial killing, virulent mycobacteria have developed a variety of mechanisms to resist this macrophage-mediated killing. These surviving mycobacteria become dormant, however, if host cellular immunity or the signals maintaining granuloma structure wane, or if mycobacteria resume replication, leading to reactivation of TB. This balance of life and death applies not only to the mycobacterium but also to the host macrophages that may undergo apoptosis or necrosis, leading to the characteristic caseous necrosis within the granuloma, and the potential spread of TB infection. The immunological factors controlling the development and maintenance of the granuloma will be reviewed.

Potential correlates of BCG induced protection against tuberculosis detected in a mouse aerosol model using gene expression profiling

Tuberculosis (TB) is responsible for more than 2 million deaths per year with the incidence of new cases rising throughout the world. Mycobacterium bovis bacillus Calmette Guerin (BCG) is currently the only available licensed vaccine against M. tuberculosis. Despite the variable protective efficacy in different populations it affords some protection, particularly against childhood and disseminated forms of the disease. BCG remains the gold standard for assessing other prospective TB vaccines, yet there is a lack of information on the mechanisms of BCG protection and consequently there are no definitive correlates of protection for this vaccine. In order to further studies in this area we assessed lung RNA homogenates from naïve, BCG vaccinated and aerosol challenged mice. We found increased IFN-gamma levels in lungs of aerosol challenged mice previously vaccinated with BCG and a number of transcripts regulated by IFN-gamma were also increased in the lungs of these animals. These transcripts represent a cluster of IFN-gamma related transcripts that may assist in determining if BCG and maybe other potential vaccines will elicit protection against M. tuberculosis.

Selective Activation of Peripheral Blood T Cell Subsets by Endotoxin Infusion in Healthy Human Subjects Corresponds to Differential Chemokine Activation

Although activation of human innate immunity after endotoxin administration is well established, in vivo endotoxin effects on human T cell responses are not well understood. Most naive human T cells do not express receptors for LPS, but can respond to endotoxin-induced mediators such as chemokines. In this study, we characterized the in vivo response of peripheral human T cell subsets to endotoxin infusion by assessing alterations in isolated T cells expressing different phenotypes, intracellular cytokines, and systemic chemokines concentration, which may influence these indirect T cell responses. Endotoxin administration to healthy subjects produced T cell activation as confirmed by a 20% increase in intracellular IL-2, as well as increased CD28 and IL-2R alpha-chain (CD25) expression. Endotoxin induced indirect activation of T cells was highly selective among the T cell subpopulations. Increased IL-2 production (36.0 +/- 3.7 to 53.2 +/- 4.1) vs decreased IFN-gamma production (33.8 +/- 4.2 to 19.1 +/- 3.2) indicated selective Th1 activation. Th2 produced IL-13 was minimally increased. Differentially altered chemokine receptor expression also indicated selective T cell subset activation and migration. CXCR3+ and CCR5+ expressing Th1 cells were decreased (CXCR3 44.6 +/- 3.2 to 33.3 +/- 4.6 and CCR5 24.8 +/- 2.3 to 12 +/- 1.4), whereas plasma levels of their chemokine ligands IFN-gamma-inducible protein 10 and MIP-1alpha were increased (61.4 +/- 13.9 to 1103.7 +/- 274.5 and 22.8 +/- 6.2 to 55.7 +/- 9.5, respectively). In contrast, CCR4+ and CCR3 (Th2) proportions increased or remained unchanged whereas their ligands, eotaxin and the thymus and activation-regulated chemokine TARC, were unchanged. The data indicate selective activation among Th1 subpopulations, as well as differential Th1/Th2 activation, which is consistent with a selective induction of Th1 and Th2 chemokine ligands.