Relatively Low Level of Antigen-specific Monocytes Detected in Blood from Untreated Tuberculosis Patients Using CD4+ T-cell Receptor Tetramers

Abstract

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.

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

“…Although, TB patients presented with a higher percentage of CD14C cells than health control, 56,57 it was confirmed that the apoptosis of macrophages was triggered after Mtb infection, 48 and the percentage of apoptotic monocytes dramatically decreased after Mtb treatment. 58 In conclusion, we elucidate a novel mechanism of host response against mycobacterial in humans. We show that miR-20a-5p is downregulated after mycobacterial infection and indirectly increased Bim expression, although the molecular mechanisms required for the reduction of miR20a-5p by mycobacterial have yet to be fully elucidated, which promotes macrophage apoptosis to facilitate mycobacterial clearance.…”

“…Since, the percentage of apoptotic monocytes dramatically decreased after treatment, 58 miR20a-5p has the potential to be a biomarker to diagnose tuberculosis and evaluate treatment outcomes.…”

Immune Response to Mycobacterial Infection: Lessons from Flow Cytometry

“…The flow cytometer performs this analysis by passing thousands of cells per second through a laser beam and capturing the light that emerges from each cell when passing through it. The data gathered can be analyzed statistically by flow cytometry software to report cellular characteristics such as size, complexity, phenotype, and health [19]. …”

“…Using CD4 + T-cell receptor tetramers, it has been shown that there is a relatively low level of Mtb -specific monocytes in the peripheral blood of patients with advanced and untreated TB compared to non-TB patients, healthy donors, and umbilical cords. This phenomenon is presumably related to the apoptosis or necrosis of antigen presenting cells such as macrophages due to live mycobacteria and their growth [19]. Elsewhere, a decreased proliferative response and production of IFN- γ affecting both CD4 + and CD8 + T cell subpopulations which occurred in active TB [30] and suppression of IL-17 + CD4 + T-cells were associated with active TB [31].…”

Role of mitochondrial oxidative stress on lymphocyte homeostasis in patients diagnosed with extra‐pulmonary tuberculosis

“…Other factors that also contribute to disease severity are T‐reg cells, low CD4/CD8 count, and suppressed gene activity. Earlier, progression in bacterial infection was reported to be inversely corelated with weak or impaired adaptive responses (Huang et al, ; Day et al, ). Lymphocytes, the known effector cells of our immune system, play an important role in providing immunologic resistance against Mycobacterium infection (Mishra et al, ).…”