Interferon gamma production in the course of Mycobacterium tuberculosis infection

It is not clear why some individuals with unknown predisposition develop tuberculosis, while others remain healthy in spite of heavy exposure. Interferon gamma (IFNgamma) is considered to be the key cytokine responsible for resistance to M. tuberculosis infection, as confirmed by increased susceptibility to mycobacterial infections in rare inherited defects in IL-12-IFNgamma axis. The aim of this study was to assess the IFNgamma production by peripheral blood lymphocytes from immunocompetent tuberculosis (TB) patients. The study group included 51 TB patients. In all cases, TB was confirmed by culture. Twenty healthy TB contacts were considered as control group. Commercially available ELISA-based assays were used to measure IFNgamma in the supernatant of whole blood cell cultures after stimulation with PWM (Phytolacca Americana), PHA (phytohemagglutynin), and PPD (purified protein derivative). No difference in IFNgamma secretion between the patients and control group was found when blood cells were stimulated by PWM or PHA. PPD-induced IFNgamma formation was higher in TB patients than in controls. The secretion of IFNgamma after non-specific stimulation varied in different clinical and radiological presentation of tuberculosis and it was lower in most advanced and extensive forms of the disease. It is unclear whether the difference in formation and release of IFNgamma is a primary or secondary phenomenon in the course of the disease.