Cellular immunity in current active pulmonary tuberculosis

Value of serum cytokine biomarkers TNF-α, IL-4, sIL-2R and IFN-γ for use in monitoring bacterial load and anti-tuberculosis treatment progress

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Serum cytokine levels may correlate with tuberculosis patient disease status.

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Serum TNF-α level may be a useful biomarker for predicting bacillar burden.

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Serum TNF-α and IFN-γ levels may reliably monitor anti-TB treatment progress.

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Serum IL-4 level had no value while serum IL-2R level value awaits further study.

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Cytokine biomarkers are useful biomarkers in clinical TB patient care settings.

Tuberculosis (TB) patient serum cytokine levels may be predictive of anti-tuberculosis treatment progress. Here, serum levels of cytokines TNF-α, IL-4, sIL-2R and IFN-γ were measured then correlated to clinical TB manifestations, bacterial burden, chest imaging findings and clinical course. Study subjects included 67 newly diagnosed pulmonary TB (PTB) patients with active disease admitted to Beijing Chest Hospital for anti-TB chemotherapeutic treatment. Blood was drawn at 0 months (pre-treatment), 1–2 months (at any time between 1 and 2 month) and after 6 months completion of treatment and serum TNF-α, IL-4, sIL-2R and IFN-γ levels were measured in duplicate using enzyme-linked immunosorbent assays (ELISAs). Correlation analysis was conducted to evaluate sensitivity and specificity of cytokine levels as predictors of disease activity and treatment progress. The results indicated that the pre-treatment serum TNF-α level of the smear-negative group was lower than that of the smear 1+ group, while serum TNF-α after 6 months completion of treatment and IFN-γ levels at 1–2 months and after 6 months completion of treatment were significantly lower, respectively, than at 0 months (before treatment) (P < 0.05). Using a cut-off value of 845 pg/ml, serum TNF-α level was predictive of treatment progress, with a sensitivity of 51%, specificity of 60% and AUC of 0.594 (P = 0.013). Meanwhile, using a cut-off value of 393 pg/ml, serum IFN-γ provided superior monitoring efficacy, with a sensitivity of 60%, specificity of 64% and AUC of 0.651 (P = 0.017). In conclusion, both serum TNF-α and IFN-γ levels might be useful biomarkers for monitoring treatment progress.

Levels of soluble VCAM-1, soluble ICAM-1, and soluble E-selectin in patients with tuberculous pleuritis

Tuberculosis is characterized by the presence of activated mononuclear cells both in the peripheral circulation and in pleural fluid. Expression and up-regulation of adhesion molecules is the basis of cell-cell adhesion in granuloma formation and in leukocyte migration to the inflammatory site. Soluble isoforms of adhesion molecules have been described, and their expression at high levels indicated an activated state. The purpose of this study was to evaluate levels of soluble adhesion molecules in serum and pleural fluid from patients with tuberculous pleural effusions, compared with non-tuberculous pleural effusions. We analysed levels of soluble vascular cell adhesion molecule-1 (s.VCAM-1), soluble intercellular adhesion molecule-1 (s.ICAM-1), and soluble E-selectin (sE-selectin) in serum and pleural fluid from patients with tuberculous pleuritis, by sandwich ELISA. Serum levels of s.ICAM-1 and s.VCAM-1 in patients with tuberculosis were higher than those in healthy controls (p < 0.001). Levels of sE-selectin levels were in the normal range compared with control groups. In pleural fluid, levels of s.VCAM-1 and s.ICAM-1 were increased in pleural effusions. Patients with tuberculous pleural effusion exhibited high levels of s.ICAM-1 compared with patients with neoplastic pleural involvement. Up-regulation of s.VCAM-1 and s.ICAM-1 in serum, along with increased levels of sE-selectin in pleural effusions from tuberculous patients, may result in transmigration of activated inflammatory cells inducing pleural damage, which may contribute to the pathological processes involved.

Examining a paradox in the pathogenesis of human pulmonary tuberculosis: immune activation and suppression/anergy

Protective immunity against Mycobacterium tuberculosis (MTB) in animal models is based on cell-mediated immunity (CMI), involving bi-directional interactions between T cells and cells of the monocyte/macrophage (MO/MA) lineage. Key factors include MO-derived interleukin (IL)-12 and tumor necrosis factor (TNF)-alpha as well as T cell derived IL-2 and interferon (IFN)-gamma. These cytokines appear particularly crucial in the induction of MA-mediated elimination of mycobacteria. Several lines of evidence indicate that similar mechanisms are operating in humans. During active pulmonary tuberculosis (PTB), signs of both immune depression and immune activation are concomitantly present. Decreased tuberculin skin test reactivity in vivo and deficient IFN-gamma production by MTB-stimulated mononuclear cells in vitro are observed. On the other hand, the serum levels of several cytokines, including TNF, and other inflammatory mediators are increased and circulating MO and T cell show phenotypic and functional evidence of in vivo activation. In this review, we will discuss the evidence for three models, which could explain this apparent paradox: 1. Stimulation of the T cell-suppressive function from MO/MA; 2. Intrinsic T cell refractoriness, possibly associated with tendency to apoptosis (programmed cell death), and 3. Compartmentalization and redistribution of immune responses to the site of disease. The opportunistic behavior of MTB during human immunodeficiency virus (HIV) infection can be explained by suppression of type-1 responses at the level of antigen-presenting cells, CD4 T cells and effector macrophages. The ominous prognostic significance of intercurrent PTB during HIV infection seems primarily due to prolonged activation of HIV replication in macrophages. Supportive immune therapy during PTB could aim at correcting the type-1 deficiency either by IFN-gamma inducers (e.g. IL-12, IL-18) or by neutralizing the suppressive cytokines transforming growth factor beta (TGF-beta) and IL-10. Alternatively, inflammatory over-activity could be reduced by neutralizing TNF. Finally, anti-apoptotic therapies (e.g. IL-15) might be considered.

Characterization of local memory cells in stage-classified pulmonary tuberculosis: preliminary observations

Immunophenotype analysis and proliferative responses were investigated in bronchoalveolar lavage (BAL) cells from 21 patients with stage-classified tuberculosis: six with localized pulmonary infiltrate (LPI); seven with diffuse pulmonary infiltrate (DPI); and eight with pleural effusions (PE). Bronchoalveolar lavage cells from these patients contained a high number of cells/ml. The macrophage number was significantly lower in the DPI group (P < 0.05) compared to the LPI or PE groups. Conversely, neutrophils were markedly increased in DPI patients compared to LPI (P < 0.01) and PE (P < 0.01) patients. Lymphocyte infiltration (97.7 +/- 2.3% CD3+, > 83% alphabeta+ and CD4+ > CD8+) was observed in the three groups. A significant increase in the number of total lymphocytes (P < 0.01) and CD4+ cells (P < 0.05) was observed in the LPI group compared to the PE group. In the LPI group CD4+CD45RO+ cell infiltration was higher than CD4+CD45RA+ cells (P < 0.001), contrasting to similar numbers of these subpopulations in the DPI group. Lymphocytes from three out of three LPI patients (alphabeta+CD4+CD45RO+) responded against tuberculin purified protein derivative contrasting to the unresponsiveness of five patients with either DPI or PE. This impaired response was reverted in two out of five patients by using peripheral blood monocytes instead of alveolar macrophages. It is suggested that, in humans, alphabetaCD4+CD45RO cells are the main lymphocyte type involved in the initial local cell-mediated immune response against Mycobacterium tuberculosis.

Immunodeficiency in non-tuberculous mycobacterial disease

T-cell immunity was investigated in eight patients with non-tuberculous mycobacterial disease, to see whether impaired immune function might be the explanation for their infection. Cellular immune function was evaluated in vitro by measuring the proliferation of peripheral blood mononuclear cells in response to both non-specific mitogens (phytohaemagglutinin and pokeweed mitogen) and specific recall antigens (streptokinase-streptodornase and purified protein derivative from Mycobacterium tuberculosis), and in vivo, by measuring the skin test response to a panel of recall antigens. Functionally relevant T-lymphocyte sub-populations (CD4, CD8, activated CD3 and gamma/delta T-cells) were enumerated by two-colour flow cytometry. The results were compared with those for a group of patients with pulmonary tuberculosis, with groups of controls matched for age and smoking habit, and with a patient group receiving steroid treatment. The patients with non-tuberculous mycobacterial disease had poor or absent skin test responses; in vitro, their response to recall antigens was depressed, although their response to mitogens was normal. The patients had significantly raised levels of CD8 lymphocytes and activated T-cells, but lacked any circulating gamma/delta T-cells. There were also differences between the various control groups. In conclusion, this study demonstrates a deficiency in the cellular immune system of these patients, which is most readily detectable by skin testing, or by measuring lymphocyte proliferative responses to recall antigens. However, the study also shows changes in cellular immune responses in controls matched for age and smoking and in patients on steroid treatment, and underscores the need for matched controls. Further work needs to be done to ascertain whether the cellular immune deficiency is a cause of, or is caused by, the mycobacterial infections, and also to investigate the pathological significance of the alterations in T-cell sub-populations.

Correlation of serum interleukin-2 receptor-alpha levels with clinical manifestations in pulmonary tuberculosis

SETTING

The analysis of serum levels of soluble interleukin-2 receptor alpha (sIL-2R-alpha) is an indirect method of studying the in vivo state of immune activation, particularly in patients with pulmonary tuberculosis (PTB) where the disease is associated with cellular immune reactions.

OBJECTIVE

To quantitate the serum sIL-2R-alpha in patients and correlate with disease activity.

DESIGN

The levels of sIL-2R-alpha were determined using ELISA in serum samples from untreated patients with PTB (n = 107), 30 of whom were later tested during treatment, household family contacts (n = 38), and healthy controls (n = 22).

RESULTS

Concentrations of sIL-2R-alpha were significantly higher in PTB patients than in controls (2845 +/- 187 vs 1217 +/- 80 pg/mL, P < 0.0001), and were even more pronounced in the sputum positive (3200 +/- 148 pg/mL) and treatment failure (3335 +/- 196 pg/mL) groups of patients. However, in household family contacts, the sIL-2R-alpha levels were found to be similar to those of healthy controls. The sIL-2R-alpha levels correlated positively with disease activity as assessed by roentgenographic findings. In six of the 16 responder patients, the sIL-2R-alpha levels fell from 3228 +/- 144 pg/mL to 1497 +/- 131 pg/mL (P < 0.0001) after 3 months of successful treatment with anti-tuberculosis drugs. However, no significant change was observed in the treatment failure patients even after one year of chemotherapy with second-line drugs.

CONCLUSION

These studies indicate that determination of serum concentrations of sIL-2R-alpha is a sensitive and specific method for monitoring disease activity in terms of T cell activation in pulmonary tuberculosis.

Effect of low-level PEEP on inspiratory work of breathing in intubated patients, both with healthy lungs and with COPD

OBJECTIVE

Evaluation of low-level PEEP (5 cm H2O) and the two different CPAP trigger modes in the Bennett 7200a ventilator (demand-valve and flow-by trigger modes) on inspiratory work of breathing (Wi) during the weaning phase.

DESIGN

Prospective controlled study.

SETTING

The intensive care unit of a university hospital.

PATIENTS

Six intubated patients with normal lung function (NL), ventilated because of non-pulmonary trauma or post-operative stay in the ICU, and six patients recovering from acute respiratory failure due to exacerbation of chronic obstructive pulmonary disease (COPD), breathing either FB-CPAP or DV-CPAP with the Bennett 7200a ventilator.

INTERVENTIONS

The patients studied were breathing with zero end-expiratory pressure (ZEEP), as well as CPAP of 5 cm H2O (PEEP), with the following respiratory modes: the demand-valve trigger mode, pressure support of 5 cm H2O, and the flow-by trigger mode (base flow of 20 l/min and flow trigger of 2 l/min). Furthermore, Wi during T-piece breathing was evaluated.

MEASUREMENTS AND RESULTS

Wi was determined using a modified Campbell's diagram. Total inspiratory work (Wi), work against flow-resistive resistance (W(ires)), work against elastic resistance (Wiel), work imposed by the ventilator system (W(imp)), dynamic intrinsic positive end-expiratory pressure (PEEPidyn), airway pressure decrease during beginning inspiration (P(aw)) and spirometric parameters were measured. In the NL group, only minor, clinically irrelevant changes in the measured variables were detected. In the COPD group, in contrast, PEEP reduced Wi and its components W(ires) and Wiel significantly compared to the corresponding ZEEP settings. This was due mainly to a significant decrease in PEEPidyn when external PEEP was applied. Flow-by imposed less Wi on the COPD patients during PEEP than did demand-valve CPAP. Differences in W(imp) between the flow-by and demand-valve trigger models were significant for both groups. However, in relation to Wi these differences were small.

CONCLUSION

We conclude that the application of low-level external PEEP benefits COPD patients because it reduces inspiratory work, mainly by lowering the inspiratory threshold represented by PEEPidyn. Differences between the trigger modes of the ventilator used in this study were small and can be compensated for by the application of a small amount of pressure support.

Serum soluble interleukin-2 receptor: a useful indicator of the clinical course in pulmonary tuberculosis

SETTING

In tuberculosis both host protection and most pathogenic mechanisms depend on T lymphocytes. After activation by mycobacterial antigens, T cells both secrete interleukin-2 (IL-2) and express a high affinity receptor for this molecule (IL-2R) on their own surface. A soluble fraction of IL-2 receptor (sIL-2R), released from cell membrane, is detectable in serum and its concentration is known to be elevated in tuberculosis.

OBJECTIVE

To ascertain the role of sIL-2R as an indicator of clinical evolution and response to antituberculosis treatment.

DESIGN

A prospective study, in which we have measured serum sIL-2R in 52 patients (42 with active and 10 with inactive pulmonary tuberculosis) and in 36 healthy controls. In 20 patients, serum sIL-2R levels were measured serially throughout the treatment. Levels of sIL-2R were correlated to clinical and radiological parameters.

RESULTS

Serum sIL-2R was significantly increased in patients with tuberculosis as compared to healthy subjects. Both the radiological findings and the clinical state of patients showed a good correlation with sIL-2R. All patients with normal values of sIL-2R 6 months after starting therapy had a favourable clinical evolution.

CONCLUSION

Serum sIL-2R is a useful marker of the clinical state and evolution of patients with pulmonary tuberculosis. The detection of permanently high values beyond 3-6 months of treatment suggests that additional drugs or prolonged administration would be advisable in order to ensure full recovery.

Cytokine gene expression by cultures of human lymphocytes with autologous Mycobacterium tuberculosis-infected monocytes

In order to better understand the immunoregulation following Mycobacterium tuberculosis infection, cytokine mRNA induction in response to in vitro infection of human monocytes with live virulent M. tuberculosis H37Rv cocultured with autologous lymphocytes was quantitated by reverse transcriptase-PCR. Induced levels of interleukin 1 beta (IL-1 beta), IL-2, tumor necrosis factor alpha, and gamma interferon (IFN-gamma) were compared among groups of individuals representing three phases of immunity to infection with M. tuberculosis: naive normal control subjects, purified protein derivative (PPD)-reactive normal donors, and individuals with active tuberculosis (TB [diseased]). Levels of IL-1 beta and tumor necrosis factor alpha mRNA in cocultured cells from TB patients were 51 and 45%, respectively, of those obtained in cells from sensitized healthy volunteers and were comparable to those from naive normal donors. Lymphoproliferative responses to M. tuberculosis and induction of the T-cell cytokine IL-2 were predictably high in the cells of PPD-sensitized donors, low in normal naive individuals, and variable among TB patients. In contrast, the induced level of another lymphokine, IFN-gamma, did not follow the pattern seen in IL-2 induction. Infection with live M. tuberculosis induced high levels of IFN-gamma mRNA in lymphocytes of both PPD-sensitized and normal naive donors compared with those of TB patients. Interestingly, polyclonal stimulation with the mitogen concanavalin A induced similar IFN-gamma levels in cells from all three donor groups. The high level of IFN-gamma induced by the infection of monocytes from naive normal donors suggests a role for natural killer (NK) cells in the production of IFN-gamma in this coculture system. This response appears independent of the role performed by T cells.

Cellular immunity in tuberculous pleural effusions: evidence of spontaneous lymphocyte proliferation and antigen-specific accelerated responses to purified protein derivative (PPD)

The kinetics of in vitro cellular proliferation against a PPD of Mycobacterium tuberculosis or streptococcal antigen (streptokinase-streptodornase) was evaluated in pleural fluid and peripheral blood mononuclear cells (PBMC) from patients with tuberculous and non-tuberculous pleuritis. The peak proliferative response to PPD by mononuclear cells from pleural fluid occurred earlier (day 3) in 65% of patients with tuberculosis, a finding not seen in non-tuberculous effusions. Spontaneous lymphocyte proliferation of both peripheral blood lymphocytes and pleural effusion lymphocytes was frequently observed, irrespective of etiology. However, 20 of 21 tuberculous patients manifesting spontaneous lymphocyte proliferation had accelerated kinetics of proliferation to PPD, which was antigen-specific. These results suggest that spontaneous lymphocyte proliferation occurs as a response to antigen stimulation at the site of disease, and is not a non-specific response to inflammation. Furthermore, enhanced reactivity against mycobacterial antigen, manifested by accelerated kinetics of proliferation, has diagnostic potential in patients with pleural effusions.