Contribution of CD8⁺ T cells to gamma interferon production in human tuberculosis

The proportions of peripheral blood mononuclear cells (PBMC), CD4⁺ T cells, and CD8⁺ T cells that produce gamma interferon (IFN-γ) in response to Mycobacterium tuberculosis were markedly reduced in tuberculosis patients, particularly in those with severe disease. Depletion of CD4⁺ but not CD8⁺ cells prior to stimulation of PBMC with M. tuberculosis abolished IFN-γ production. These results show that (i) IFN-γ production by CD8⁺ and CD4⁺ cells correlates with the clinical manifestations of M. tuberculosis infection and (ii) IFN-γ production by CD8⁺ cells depends on CD4⁺ cells.