Induction of cell apoptosis is one of the major host defense mechanisms through which macrophages control Mycobacterium tuberculosis (Mtb) infection. However, the mechanisms underlying macrophage apoptosis triggered by Mtb infection are still largely unknown. In this study, a microarray profiling survey revealed 14 miRNAs were down-regulated in CD14+ monocytes from active pulmonary tuberculosis patients, and only the reduction of miR-20a-5p could be reversed after successful anti-tuberculosis treatment. Validation of miR-20a-5p expression was confirmed using real time qPCR. Moreover, miR-20a-5p expression also decreased in differentiated THP-1 macrophages after mycobacterial infection in vitro. Functional assays through forced or inhibited expression of miR-20a-5p in THP-1 macrophages demonstrated that miR-20a-5p functioned as a negative regulator of mycobacterial-triggered apoptosis. Importantly, inhibition of miR-20a-5p expression resulted in more efficient mycobacterial clearance from infected ...

https://www.tandfonline.com/doi/pdf/10.1080/15384101.2016.1215386

Down-regulation of miR-20a-5p triggers cell apoptosis to facilitate mycobacterial clearance through targeting JNK2 in human macrophages.

The development of in situ major histocompatibility complex (MHC) tetramer (IST) staining to detect antigen (Ag)-specific T cells in tissues has radically revolutionized our knowledge of the local cellular immune response to viral and bacterial infections, cancers, and autoimmunity. IST combined with immunohistochemistry (IHC) enables determination of the location, abundance, and phenotype of T cells, as well as the characterization of Ag-specific T cells in a 3-dimensional space with respect to neighboring cells and specific tissue locations. In this review, we discuss the history of the development of IST combined with IHC. We describe various methods used for IST staining, including direct and indirect IST and IST performed on fresh, lightly fixed, frozen, and fresh then frozen tissue. We also describe current applications for IST in viral and bacterial infections, cancer, and autoimmunity. IST combined with IHC provides a valuable tool for studying and tracking the Ag-specific T cell immune response in tissues.

/pdf/detection-of-antigen-specific-t-cells-using-in-situ-mhc-b1xxujhj2f.pdf

Detection of Antigen-Specific T Cells Using In Situ MHC Tetramer Staining.

In Vivo Induction of Apoptosis in the Thymus by Administration of Mycobacterial Cord Factor(Trehalose 6,6′-Dimycolate)(抗酸菌ミコール酸含有糖脂質による胸腺におけるアポトーシスの誘導について)

Mycobacterium tuberculosis (Mtb) causes human tuberculosis, and more people die of it than of any other pathogen in the world. Immunodominant antigens elicit the large majority of T cells during an infection, making them logical vaccine candidates. Yet, it is still unknown whether these immunodominant antigenspecific T cells recognize Mtb-infected cells. Two immunodominant antigens, TB10.4 and Ag85b, have been incorporated into vaccine strategies. Surprisingly, mice vaccinated with TB10.4 generate TB10.4-specific memory CD8 T cells but do not lead to additional protection compared to unvaccinated mice during TB. Ag85b-specific CD4 T cells are also generated during vaccination, but the literature on whether these cells recognize Mtb-infected cells is also inconsistent. We demonstrate that TB10.4-specific CD8 T cells do not recognize Mtbinfected cells. However, under the same conditions, Ag85b-specific CD4 T cells recognize Mtb-infected macrophages and inhibit bacterial growth. In contrast, polyclonal CD4 and CD8 T cells from the lungs of infected mice can specifically recognize Mtb-infected macrophages, suggesting macrophages present antigens other than the immunodominant TB10.4. The antigen location may also be critical for presentation to CD8 T cells, and live Mtb may inhibit antigen presentation of TB10.4. Finally, we propose that TB10.4 is a decoy antigen as it elicits a robust CD8 T cell response that poorly recognizes Mtb-infected macrophages, allowing Mtb to evade host immunity.

/pdf/antigen-specific-cd4-and-cd8-t-cell-recognition-during-2wjg22x0sz.pdf

Antigen Specific CD4+ and CD8+ T Cell Recognition During Mycobacterium Tuberculosis Infection

Detecting and treating active and latent tuberculosis are pivotal elements for effective infection control; yet, due to their significant inherent limitations, the diagnostic means for these two stages of tuberculosis (TB) to date remain suboptimal. This paper reviews the current diagnostic tools for mycobacterial infection and focuses on the application of flow cytometry as a promising method for rapid and reliable diagnosis of mycobacterial infection as well as discrimination between active and latent TB: it summarizes diagnostic biomarkers distinguishing the two states of infection and also features of the distinct immune response against Mycobacterium tuberculosis (Mtb) at certain stages of infection as revealed by flow cytometry to date.

/pdf/immune-response-to-mycobacterial-infection-lessons-from-flow-py8923kp0q.pdf

Immune Response to Mycobacterial Infection: Lessons from Flow Cytometry

The in vivo kinetics of antigen-presenting cells (APCs) in patients with advanced and convalescent tuberculosis (TB) is not well characterized. In order to target Mycobacterium tuberculosis (MTB) peptides- and HLA-DR-holding monocytes and macrophages, 2 MTB peptide-specific CD4+ T-cell receptor (TCR) tetramers eu and hu were successfully constructed. Peripheral blood (PBL) samples from inpatients with advanced pulmonary TB (PTB) were analyzed using flow cytometry, and the percentages of tetramer-bound CD14+ monocytes ranged from 0.26–1.44% and 0.21–0.95%, respectively; significantly higher than those measured in PBL samples obtained from non-TB patients, healthy donors, and umbilical cords. These tetramers were also able to specifically detect macrophages in situ via immunofluorescent staining. The results of the continuous time-point tracking of the tetramer-positive rates in PBL samples from active PTB outpatients undergoing treatment show that the median percentages were at first low before treatment, increased to their highest levels during the first month, and then began to decrease during the second month until finally reaching and maintaining a relatively low level after 3–6 months. These results suggest that there is a relatively low level of MTB-specific monocytes in advanced and untreated patients. Further experiments show that MTB induces apoptosis in CD14+ cells, and the percentage of apoptotic monocytes dramatically decreases after treatment. Therefore, the relatively low level of MTB-specific monocytes is probably related to the apoptosis or necrosis of APCs due to live bacteria and their growth. The bactericidal effects of anti-TB drugs, as well as other unknown factors, would induce a peak value during the first month of treatment, and a relatively low level would be subsequently reached and maintained until all of the involved factors reached equilibrium. These tetramers have diagnostic potential and can provide valuable insights into the mechanisms of antigen presentation and its relationship with TB infection and latent TB infection.

/pdf/relatively-low-level-of-antigen-specific-monocytes-detected-300ge0ppcg.pdf

Relatively low level of antigen-specific monocytes detected in blood from untreated tuberculosis patients using CD4+ T-cell receptor tetramers.

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Relatively low level of antigen-specific monocytes detected in blood from untreated tuberculosis patients using CD4+ T-cell receptor tetramers.