Fig. 1.

Scatter plot of the magnitude of tuberculosis (TB) antigen-specific immune responses against CD4 (a) and CD8 (b) T cell counts. The sum of interferon (IFN)-γ spots/10⁶ peripheral blood mononuclear cells (PBMC) in response to TB-specific peptide pools early secretory antigen target-6 (ESAT-6) and culture filtrate protein-10 (CFP-10) are plotted against CD4 (a) and CD8 (b) T cell counts observed in each individual who had a positive test result. Open circles represent patients with active/probable tuberculosis, closed circles represent patients with latent TB infection. A positive TB enzyme-linked immunospot assay was defined as follows: the sum of the IFN-γ spots to both peptide pools exceeds that seen in the medium alone well by 25. In this set of experiments the number of IFN-γ spots seen in medium alone well in each individual was < 4 spots/10⁶ PBMC.