CD4 and tuberculosis: The QFT-Plus assay includes a second antigen tube (TB2) containing processed ESAT-6/CFP-10 peptides that are optimized to elicit a CD8+ T-cell response in addition to the CD4+ response, with the intention to increase sensitivity based on higher CD8+ T-cell responses in cases of recent MTB exposure, TB and individuals with low CD4+ T-cell counts (TB/HIV-coinfection, children aged < 5 years) (Shafeque et al. 2020).