The frequencies of PPD- and RD1-peptide-specific CD8+ IFN-γ-only producing cells were significantly higher in active tuberculosis than in latent tuberculosis infection (P = .017 and .016, respectively), as was the frequency of CD8+ PPD-specific cells secreting both IFN-γ and TNF-α (P = .013; Figure 1C). This evidence concerns the gene IFNG and tuberculosis.