The source of Mycobacterium tuberculosis-specific IFN-γ production in peripheral blood mononuclear cells of TB patients

Platelets correlate with false negative T-SPOT.TB results by inhibiting interferon-γ production in T cells via degranulation

Background

T-SPOT.TB (T-SPOT) is widely used for the detection of Mycobacterium tuberculosis infection by detecting interferon-gamma (IFN-γ) release in T lymphocytes. This assay is performed on peripheral blood mononuclear cells (PBMCs) separated by Ficoll density gradient centrifugation, which often contain some residual platelets. Here, we investigated the impact of platelets on T-SPOT assay and related mechanisms.

Methods

The correlation between platelet count, platelet-to-lymphocyte ratio (PLR), and the IFN-γ secreting T cells (ISCs) in positive control wells of T-SPOT assay were retrospectively analyzed. T-SPOT assay was performed with un-treated PBMCs, platelets-removed PBMCs, and platelets-enriched PBMCs to confirm the impact of platelets on T-SPOT assay. The activation of platelets and their impact on IFN-γ production in T cells were detected by flow cytometry (FCM). Platelets and T cells were cultured in a mixed culture system and co-culture system respectively, followed by detection of the frequencies of IFN-γ-producing T cells and the levels of intracellular IFN-γ in T cells by FCM. Moreover, the effect of platelet releasate on the T-SPOT assay was evaluated.

Results

The ISCs in positive control wells of the T-SPOT assay showed a significant decrease with the increase in platelet count. The PLR of the peripheral blood were negatively correlated with the ISCs in positive control wells of the T-SPOT assay. Removal or enrichment of platelets significantly increased or decreased the ISCs and the positive rate of T-SPOT. Inhibition of platelet activation significantly increased the ISCs of T-SPOT. The frequencies of IFN-γ-producing T cells in PBMCs and the levels of intracellular IFN-γ were significantly reduced by the addition of platelets, both in the mixed culture system and the co-culture system. Platelet releasate upon thrombin activation significantly decreased the ISCs of T-SPOT.

Conclusions

Platelets correlate with negative T-SPOT results by inhibiting IFN-γ production in T cells via degranulation.

Exploring key molecular signatures of immune responses and pathways associated with tuberculosis in comorbid diabetes mellitus: a systems biology approach

Background

Comorbid type 2 diabetes mellitus (T2DM) increases the risk for tuberculosis (TB) and its associated complications, although the pathological connections between T2DM and TB are unknown. The current research aims to identify shared molecular gene signatures and pathways that affirm the epidemiological association of T2DM and TB and afford clues on mechanistic basis of their association through integrative systems biology and bioinformatics approaches. Earlier research has found specific molecular markers linked to T2DM and TB, but, despite their importance, only offered a limited understanding of the genesis of this comorbidity. Our investigation used a network medicine method to find possible T2DM-TB molecular mediators.

Results

Functional annotation clustering, interaction networks, network cluster analysis, and network topology were part of our systematic investigation of T2DM-TB linked with 1603 differentially expressed genes (DEGs). The functional enrichment and gene interaction network analysis emphasized the importance of cytokine/chemokine signalling, T cell receptor signalling route, NF-kappa B signalling pathway and Jak-STAT signalling system. Furthermore, network analysis revealed significant DEGs such as ITGAM and STAT1, which may be necessary for T2DM-TB immune responses. Furthermore, these two genes are modulators in clusters C4 and C5, abundant in cytokine/chemokine signalling and Jak-STAT signalling pathways.

Conclusions

Our analyses highlight the role of ITGAM and STAT1 in T2DM-TB-associated pathways and advances our knowledge of the genetic processes driving this comorbidity.

STAT1 and its related molecules as potential biomarkers in Mycobacterium tuberculosis infection

Tuberculosis (TB) is a severe infectious disease that seriously endangers human health. The immune defence mechanism of the body against TB is still unclear. The purpose of this study was to find the key molecules involved in the immune defence response during TB infection, and provide reference for the treatment of TB and further understanding of the immune defence mechanism of the body. Data from http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE83456 were downloaded from GEO data sets for analysis, and a total of 192 differentially expressed genes were screened out. Most of these genes are enriched in the interferon signalling pathway and are defence response–related. We also found that STAT1 plays an important role in the immune defence of TB infection and it is one of the key genes related to interferon signalling pathway. STAT1‐related molecules including hsa‐miR‐448, hsa‐miR‐223‐3p, SAMD8_hsa_circRNA 994 and TWF1_hsa_circRNA 9897 were therefore screened out. Furthermore, expression levels of hsa‐miR‐448 and hsa‐miR‐223‐3p were then verified by qRT‐PCR. Results showed that both hsa‐miR‐448 and hsa‐miR‐223‐3p were down‐regulated in plasma from patients with pulmonary TB. Taken together, our data indicate that an mRNA‐miRNA‐circRNA interaction chain may play an important role in the infection of MTB, and STAT1 and related molecules including hsa‐miR‐223‐3p, has‐miR‐448, SAMD8_hsa_circRNA994 and TWF1_hsa_circRNA9897 were identified as potential biomarkers in the development of active TB.

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.

The performance of the TBAg/PHA ratio in the diagnosis of active TB disease in immunocompromised patients

OBJECTIVES

The results of the T-SPOT.TB (T-SPOT) assay are reduced in immunocompromised patients with active tuberculosis (ATB), and it is difficult using T-SPOT results to distinguish ATB from latent tuberculosis infection (LTBI) in this condition. The aim of this study was to determine the performance of the TBAg/PHA ratio in T-SPOT assay in the diagnosis of ATB in immunocompromised patients.

METHODS

One hundred and forty three immunocompromised ATB patients and 124 LTBI individuals were diagnosed according to conventional tests and T-SPOT assay.

RESULTS

The results of T-SPOT assay are of no value in the diagnosis of ATB in immunocompromised patients. However, the number of phytohaemagglutinin (PHA) spot-forming cells (sfc) in T-SPOT assay was substantially decreased in immunocompromised ATB patients compared with that in LTBI individuals. Receiver operating characteristic (ROC) analysis revealed that a further calculation of the TBAg/PHA ratio (the larger of the ESAT-6/PHA and CFP-10/PHA) showed a better performance in distinguishing these two diseases. Using the threshold value of 0.316, the sensitivity and specificity for distinguishing immunocompromised ATB patients from LTBI individuals were respectively 79.21 and 94.05%.

CONCLUSIONS

Our findings suggest that the TBAg/PHA ratio might have some significance for the diagnosis of TB disease in immunocompromised patients.

Association of MBL2, TLR1, TLR2 and TLR6 Polymorphisms With Production of IFN-γ and IL-12 in BCG Osteitis Survivors R1

BACKGROUND

Interferon-gamma (IFN-γ) is a key cytokine in defense against mycobacteria, including Bacillus Calmette-Guérin (BCG). Mannose-binding lectin (MBL) and toll-like receptors (TLRs) are pattern-recognizing molecules of innate immunity. The aim of the present study was to investigate the relationship between polymorphisms in MBL, TLR1, TLR2 and TLR6 encoding genes and stimulated IFN-γ and interleukin-12 (IL-12) ex vivo production in BCG osteitis survivors.

METHODS

Data on single nucleotide polymorphisms in the MBL2 gene and TLR1, TLR2 and TLR6 genes were available from 132 former BCG osteitis patients, and data on ex vivo IFN-γ and IL-12 production were available from 115 and 118 patients, respectively. The present study is a secondary analysis of these available data. In an earlier study, we were able to characterize low IFN-γ and low IL-12 producers after BCG+IL-12 or BCG+IFN-γ stimulations, respectively.

RESULTS

Three patients had the homozygous variant MBL2 genotype, and one of them was a low IFN-γ producer (both concentration and response <5th percentile). The heterozygous variant MBL2 genotype showed no association with IFN-γ or IL-12 production. The TLR2 variant genotype was present in 14 subjects; 28.6% of them were low IFN-γ producers versus 7.8% of those 103 with the TLR2 wild genotype (P = 0.037). TLR1 or TLR6 polymorphisms had no significant associations with stimulated ex vivo IFN-γ or IL-12 production.

CONCLUSIONS

Preliminary evidence was found that variant genotypes of the MBL2 gene (if homozygous) and variant genotypes of the TLR2 gene (only heterozygotes present) are associated with low IFN-γ production.