Compared with healthy tuberculin reactors, Mycobacterium tuberculosis-stimulated peripheral blood mononuclear cells from tuberculosis patients had diminished production and mRNA expression of the Th1 cytokines gamma interferon and interleukin 2 (IL-2), with no change in production and mRNA expression for the Th2 cytokines IL-4, IL-10, and IL-13. These results were confirmed by evaluation of T cells and CD4+ cells. At the level of systemic T cells, development of tuberculosis is associated with diminished Th1 but not enhanced Th2 responses.