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

Abstract

The proportions of peripheral blood mononuclear cells (PBMC), CD4(+) T cells, and CD8(+) T cells that produce gamma interferon (IFN-gamma) 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-gamma production. These results show that (i) IFN-gamma production by CD8(+) and CD4(+) cells correlates with the clinical manifestations of M. tuberculosis infection and (ii) IFN-gamma production by CD8(+) cells depends on CD4(+) cells.

FIG. 1

Frequency of IFN-γ-producing cells in stimulated PBMC. PBMC were obtained from six healthy tuberculin-negative persons (PPD−), nine healthy tuberculin reactors (PPD+), nine patients with moderately advanced tuberculosis (MA), and six patients with far advanced tuberculosis (FA). The frequency of IFN-γ-producing cells upon stimulation with M. tuberculosis (A) or PHA (B) was determined by ELISPOT. Each circle represents the number of IFN-γ-producing cells per 10⁵ cells for one person. The horizontal bars indicate median values.

FIG. 2

Frequency of IFN-γ-producing CD8⁺ cells (A) and CD4⁺ cells (B) in M. tuberculosis-stimulated PBMC. PBMC were obtained from six healthy tuberculin-negative persons (PPD−), nine healthy tuberculin reactors (PPD+), nine patients with moderately advanced tuberculosis (MA), and six patients with far advanced tuberculosis (FA). The frequency of IFN-γ-producing cells after stimulation with M. tuberculosis was determined by ELISPOT. Each circle represents the number of IFN-γ-producing cells per 10⁵ CD8⁺ or CD4⁺ cells for one person. The horizontal bars indicate median values.

FIG. 3

IFN-γ production per CD8⁺ cell (A) and CD4⁺ cell (B). IFN-γ production per cell was estimated by measuring the density of spots on the ELISPOT plates for healthy tuberculin reactors and tuberculosis patients shown in Fig. 2, using an integrated image analysis system. The y axis shows spot density in arbitrary units. Each circle represents the mean spot density for one person. The horizontal bars indicate median values.

FIG. 4

Effect of depletion of CD8⁺ or CD4⁺ cells on IFN-γ production. PBMC, CD8-depleted PBMC, and CD4-depleted PBMC from three healthy tuberculin reactors were cultured with M. tuberculosis for 72 h. The frequency of IFN-γ-producing cells per 10⁵ cells was determined by ELISPOT (A), and IFN-γ concentrations in supernatants were measured by enzyme-linked immunosorbent assay (B). Mean values and standard errors are shown.