Figure 1.

Figure shows both in vivo (TST test) and in vitro (IGRAs) release of inflammatory cytokines by T-cells sensitized to mycobacterial antigens. In the skin test, antigens are injected intra dermally which bring specific lymphocytes to the site causing release of cytokines resulting in induration. In the blood test, mononuclear cells from peripheral blood produce IFN-γ from sensitized T-cells which is measured by ELISA.[6] Adapted from: Andersen P, Munk ME, Pollock JM, et al. Specific immune- based diagnosis of tuberculosis. Lancet 2000;356:1099-04