CD4 and tuberculosis: Interestingly, patients with active tuberculosis had higher frequencies of PPD reactive cytokine-positive CD4 T cells (median 0.81%, interquartile range (IQR) from 0.35–1.73%) than individuals with successfully treated disease (median 0.39%, IQR 0.10–0.73%, p = 0.02, Mann-Whitney test, figure 1).