Cytokines as Immunological Markers for Follow up of Disease Activity During the Treatment of Pulmonary Tuberculosis

Abstract

Background: Cytokines play a major role in protection against Mycobacterium tuberculosis infection and regulate the immune responses at a cellular level. Cytokine profile determines clinical outcome of the disease and responses to treatment as well. A T helper 1 (Th1) cytokine interferon gamma (IFN-U) is one of the most important cytokines which activate the macrophages to produce tumor necrosis factor-alpha (TNF-V). Excessive production of TNF-V have been implicated in immunopathogenesis of tuberculosis. A T helper 2 (Th2) response leads to release of IL-4, and IL-10 promoting an anti-inflammatory macrophage response. Interleukin-4(IL-4), has been implicated to down-regulate IFN-U, and thus has a harmful effect on TB patients. IL10 cytokine has the
capacity to inhibit Th1 activation and thus terminates cell mediated immune responses.
Objective:The objective of the present study was to determine Th1 and Th2 cytokine profile in patients with tuberculosis to identify immunological marker for follow up of the disease activity, and to study the outcome of treatment.
Methods: To examine this, blood samples were collected from newly diagnosed HIV negative pulmonary tuberculosis patients and from apparently healthy individuals as controls following an informed consent. Blood samples were as well collected at several intervals during the treatment with anti-tuberculosis drugs. Levels of IFN-U, TNF-V, IL-4 and IL-10 were measured pre and during treatment using commercial available enzyme-linked immune-sorbent assay (ELISA). Data were analyzed using SPSS 20. Receiver Operating Characteristic (ROC) Curve analysis has been
carried out to assess their discriminative power and to determine cut-off values. Analysis has been carried out further by calculating other measures of diagnostic test accuracy.
Results: The median serum level of IL-4 was 20 and 35 pg/ml higher in new cases (untreated patients) and in patients under treatment with oral anti-tuberculosis, respectively, compared with that of controls (p=001). Levels of TNF- were significantly increased in patients before and after
the treatment than those in control (p=0.001). New cases had the highest median level (10pg/ml) followed by those under treatment group (6pg/ml). Levels for IFN-U were not statistically different between patients and controls (p=0.351). Median levels of IL10 were similar in both controls and new cases groups (35pg/ml), but lower in patients under treatment group (20pg/ml). Increase in levels of IL-4 during treatment showed that Th2 immune responses still present and may indicate active disease and thus IL4 cytokine may be a possible marker for the disease activity.
Conclusion: serum levels of TNF- in TB patients is useful in the evaluation of the disease activity during therapy, not replacing clinical parameters of disease activity in TB. Similar to TNF-, IL-4 can also be used as marker for TB severity. On the other hand IL-4test can be used to diagnose TB
in highly exposed suspects where a positive result is more likely to indicate TB.

Keywords: Tuberculosis; Cytokines; Immunological markers.