Differences in PPD- and mitogen-induced T-cell activation marker expression characterize immunopathology in acute...

Impaired T-cell responses to mitogens and high T-cell activation marker (TAM) expression on Mycobacterium tuberculosis-specific T-cells characterize immunopathology in patients with tuberculosis (TB). In a study of patients with TB (n = 60) and asymptomatic contacts (controls, n = 37), we found that TB patients had higher CD38⁺ T-cell proportions specific for M. tuberculosis protein (PPD_Mtb), yet total proportions of PPD_Mtb-specific T-cells were comparable. Notably, both activated (CD38⁺) and total IFN-γ⁺ T-cells from TB patients had lower mitogen (phytohemagglutinin, PHA)-induced responses. This impaired mitogen response improved the classification efficacy of the TAM-TB assay, especially employing the PPD/PHA-induced T-cell ratio.