Circulating interleukin-18 and osteopontin are useful to evaluate disease activity in patients with tuberculosis.

BACKGROUND

T helper type 1 (Th1) responses have been implicated in the protective immunity, pathophysiology and development of tuberculosis. However, it is still unclear which molecule(s) reflect disease activity in patients with tuberculosis.

METHODS

By specific enzyme immunoassays, circulating interferon-gamma. (IFN-gamma), interleukin-12 (IL-12), IL-18 and osteopontin (OPN) were measured in 47 patients with pulmonary tuberculosis and 7 patients with miliary tuberculosis before anti-tuberculosis therapy, and also measured in 19 patients with tuberculosis before and after anti-tuberculosis therapy.

RESULTS

Circulating IFN-gamma, IL-18 and OPN levels were significantly higher in patients with pulmonary tuberculosis than in healthy controls, while there was no significant difference in levels of circulating IL-12 between tuberculosis patients and controls. Circulating IFN-gamma, IL-12, IL-18 and OPN paralleled the extent of lung lesions, and circulating IFN-gamma, IL-18 and OPN paralleled the magnitude of fever in patients with pulmonary tuberculosis. Patients with miliary tuberculosis had extremely high levels of circulating OPN, IFN-gamma and IL-18. Circulating IL-18 and OPN were significantly decreased with anti-tuberculosis therapy, whereas circulating IL-12 and IFN-gamma were not.

CONCLUSIONS

Among Th1 response associated molecules, circulating levels of IL-18 and OPN, but not IFN-gamma or IL-12, reflect disease activity in patients with tuberculosis.